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Sugarcane
Dr. Gururaj Hunsigi Director
Kamataka Institute of Applied Agricultural Research (KIAAR) Sameerwadi, Bagalkot
Prism Books Pvt Ltd • Bangalore • Calcutta • Hyderabad
A2281096XB
Sugarcane in Agriculture and industry
Prism Books Pvt Ltd 1865, 32nd Cross, BSK II Stage, Bangalore - 560 070 http://www.prismbooks.com
© 2001 by Publisher
Author: Dr. Gururaj Hunsigi
Price: Rs. 950/- US $ 49.95 (including postage)
No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any information storage and retrieval system, without permission in writing from the publisher.
ISBN: 81-7286-149-4
Printed in India at Eastern Press Pvt Ltd., Bangalore.
DEDICATED TO
PADMA BHUSHAN, PUJYA K.J. SOMAIYA
Foreword
Sugarcane is one of the most important commercial crops in our country, next only to cotton, since ages. Of late, however, it has had a roller-coaster ride with cycles of surplus and shortage. It has come to occupy an important position as a crop both in tropics and subtropics.
The earliest reference to sugarcane is in Atharvaveda (5000 years ago). The ancient India knew the art and science of making sugar. Sugar was made as early as 3000 B.C. By 100 A.D., bagasse was used as captive fuel. The Sanskrit word 'Sarkara' is adopted in many languages; Sugar (English), Zucker (German), Azacar (Spanish), Sucre (French), Shakhar (Marathi), Sakar (Gujarati), Shakkar (Hindi) etc. Interestingly, sugar does not find a place in Holy Quran or Holy Bible. Instead, honey is mentioned. Thus, Alexander the Great called it as 'honey reed' and noted it as a 'closely spaced well husbanded garden crop'. There is ample evidence to claim that India is the home of sugarcane and the world owes it to India for cane sugar and its derivatives.
Sugarcane plays a key role in the Indian economy. With 480 sugar factories located in the rural areas through out the country, the Indian sugar industry is a prime catalyst in converting the potential agro-industrial rural sector into economic strength of the country. Over 45 million farmers are involved in sugarcane cultivation, harvesting and ancillary activities. The industry employs over 5 lakh skilled and unskilled workers mainly from the rural areas. Thus, over 7.5% of our rural population is directly or indirectly dependent on the sugar industry.
The industry's contribution to the Indian economy is enormous. With a total turn over of more than Rs. 20,000 crores per year, the Indian sugar industry is amongst the largest tax payers to the Central and State exchequers contributing around Rs. 1000 crores per annum. In any other country, an industry of this size and contribution would have received utmost attention and assistance from the Government. In India, the sugar industry remains comparatively neglected and its potential has not been fully harnessed.
Be that as it may, during the past 50 years, this crop has metamorphosed from sugarcane to fibre cane to alcohol cane and to energy cane. Hence a few factories have diversified into by-products based industries and have invested and put up distilleries, organic chemical plants, paper and board factories etc. But the emphasis is now on cogeneration of power. The sugar industry has the potential to generate 3000 MW of surplus power. The emerging technologies indicate that 5000 T C D plant can easily export about 18 MW power to the grid with high pressure (above 60 ATA), high temperature
(above 480°C) and high efficiency boilers with a double extraction cum condensing
turbines with hardly any additional consumption of fuel.
Sugarcane in Agriculture and Industry authored by Dr. Gururaj Hunsigi is a comprehensive handbook. It deals with every aspect of sugarcane, both from agricultural and industrial point of view. There are 28 chapters dealing with topics such as the origin, distribution and botany of sugarcane, varieties, production practices etc.
The varietal development since 50s to present day rich, short duration and early yielding varieties finds a prominent place in the book. The soil and climatic requirements of cane are well documented. The author has not lost sight of ratoon cane management since ratoons cost less but add to the sugarcane economy and hence this aspect has received due attention. The recenr innovations in transgenic sugarcane and simulation models are very well narrated.
As suppliers of raw material, sugarcane farmers play a key role in the sugar industry. Therefore, various cane developmental activities have been described. The readers would find it useful to also know about the various sugar policies evolved from time to time, since independence.
The main advantage of growing cane lies in its economics. Hence, there has been an appreciable endeavour to present the economics of cane cultivation. A chapter on tissue culture deals with the basics of this technology with special reference to sugarcane. Lastly, the fundamental steps involved in sugar processing are given in the chapter on the manufacturing of sugar.
In a very modest way, Dr. Gururaj Hunsigi's book on sugarcane aims to ultimately
achieve higher productivity of cane and sugar. It is hoped that this book would be
useful to cane development staff, factory personnel, administrators, policy makers,
students, cane growers and the general elite who are interested in this 'honey reed'.
Dr. Shantilal K. Somaiya
Chairman Somaiya Group of Industries
Preface Sugarcane cultivation and jaggery making is one of the oldest occupations in India, strengthening the rural economy. With the passage of time, great strides have been made in improving the yield and quality of sugarcane. The percapita consumption of sugar has nearly doubled since independence. Keeping in pace with the demand, there has been a phenomenal increase in the number of sugar factories in the country.
The book Sugarcane in Agriculture and Industry is written in the backdrop of this scenario. It is meant to serve as a complete handbook for students, teachers, planners, administrators, farmers, sugar industry personnel and the general elite interested in the sweet crop. The book deals with future farming of sugarcane and sugar processing to meet the demands of 2 1 " century.
Great emphasis is placed on the production practices, varieties, pest, disease and weed management. Recent innovations in tissue culture and precision engineering through sugarcane simulation models and transgenics with environmental safety are elaborately discussed.
A great deal of work has gone into making the book comprehensive by incorporating an introductory chapter on sugar manufacture, glossary, bibliography and subject index. I do hope the readers will find the book informative, instructive, engaging and worth reading.
I take this opportunity to express my heartfelt gratitude to Dr. S. K. Somaiya, Chairman of the Somaiya Group of Industries as well as Sri Samir S. Somaiya and Sri P. M. Kavadia for their constant patronage.
The book is made possible by the love and affection showered by my family Indumathi, Satish, Rajashree, Dr. Prahallad, Pusrushottam, Dr. Pratibha, Roopa and grand children Nitin, Vibha and Kartik.
Dr. Gururaj Hunsigi
Acknowledgements
The author places on record his deep sense of gratitude to:
Sri Mydur Anand, Sugar Consultant, Bangalore
Sri S. C. Srivastava, Lucknow
Dr. K. Krishna Murthy, Former Vice Chancellor, UAS, Bangalore
Dr. K. Perumal, Bangalore
Dr. K. Mohan Naidu, Dr. T. V. Sreenivasan, Dr. T. R. Srinivasan, Dr. B. Sundara and Dr. K. V. Bhagyalaxmi, Sugarcane Experts, Sugarcane Breeding Institute, Coimbatore
Dr. D. G. Hapase, Dr. G. K. Zende and Dr. G. P. Gokhale, Pune
Dr. R. L. Yadav, Meerut
Dr. H. N. Shahi, Dr. S. Solomon and Dr. S. R. Mishra, IISR, Lucknow
Sri V. B. Bagal, Director (W), Godavari Sugar Mills, Sameerwadi
Sri EG. Satpute, Asst. Director, KIAAR, Sameerwadi
Sri Vithal Rao Bakshi, Mudhol
Sri B. S. Gurumurthy, Sugar Consultant, Bangalore
Dr. M. A. Singlachar and Dr. B. R. Hegde, Former Directors of Research, UAS, Bangalore
Dr. B. Shivaraj, Dr. H. V. Nanjappa and Dr. Andani Gowda, Professors, UAS, Bangalore
Dr. C. Shankariah, Dr. N. Krishna Murthy and Dr. L.G. K. Naidu, UAS, Bangalore
Dr. Prabhanjan Rao, Hyderabad.
Contents
1. Exordium 1
1.1 Table top sweeteners 2
1.2 Cane vs beet sugar 3
1.3 Economic importance 4
1.4 Productivity of sugarcane 6
1.5 Sugarcane growing regions of India 8
1.6 Non-sacchariferous plants 10
2. Origin, history, and distribution 14
3. Related species and genera 16
3.1 Related species and general description 16
3.2 Nobilization products 20
4. Botany of sugarcane 22
5. Physiology of sugarcane 26
5.1 Sucrose: the main currency 29
6. Varieties in sugarcane 30
6.1 An era of the early and short duration variety 43
7. Flowering: a bane in commercial plantation 47
8. Sugarcane soils 51
8.1 Problem soils 57
Contents
9. Ecology of sugarcane 60
9.1 Temperature 65
9.2 Rainfall 66
9.3 Relative humidity (RH) 66
9.4 Atmospheric CO2 concentration 67
9.5 Sunlight 61
9.6 Frost 69
9.7 Wind 69
9.8 Microclimate 69
9.9 Effect of greenhouse gases (GHGs) 70
9.10 Effect of climate on ripening 70
10. Production practices 72
10.1 Preparatory tillage 72
10.2 Green manuring and application of bulky manures 75
10.3 Seed material and seed rate 76
10.4 Geometry of planting and planting depth 77
10.5 Planting period 78
10.6 Agronomy of late planted crop 80
10.7 Planting methods 81
10.7.1 Flat method of planting 81
10.7.2 Trench or Java method of planting 81
10.7.3 Partha method of planting 82
10.7.4 Deep trench planting 83
10.7.5 Rayungan method or Rajoeng method of planting 84
10.7.6 Seblang or sprouted bud method of planting 84
10.7.7 Distance planting method 85
10.7.8 Align method of planting 85
10.7.9 Tjeblock method of planting 85
10.7.10 Modified trench system of planting 86
10.7.11 Contour system of planting 87
10.7.12 Single bud direct planting 87
10.7.13 Chip bud or bud chip technique of planting 87
Sugarcane in agriculture and industry
10.7.14 Pit planting 88
10.7.15 Skip-furrow planting 89
10.7.16 Paired-row planting 89
10.7.17 IISR 8626 method of planting 91
10.7.18 Ring planting 91
10.7.19 Spaced transplanting technique (STP) 93
10.7.20 Polybag seedling transplanting method 94
10.7.21 Ridges and furrows method of planting 95
10.8 Mechanical planters 96
10.9 Aftercare 97
10.10 Managing canes under stress conditions 97
10.10.1 Cold stress 98
10.10.2 Agronomy of waterlogged or excess moisture conditions 98
10.10.3 Moisture stress conditions 100
10.10.4 Managing acid soils 102
10.10.5 Managing saline-alkali soils 103
10.10.6 Sugarcane in Tilah land and shallow black soils 105
10.11 Sugarcane based cropping and farming systems 105
10.11.1 Companion cropping in sugarcane 112
10.11.2 Sugarcane based farming systems 118
11. Nutrition and fertiliser management 124
.1 Nutrient uptake and removal 124
11.2 Nitrogen 125
11.2.1 Nitrogen losses 129
11.2.2 N carriers 130
11.2.3 Varietal response 132
11.2.4 Time and method of N application 134
11.2.5 The rhizosphere 135
11.2.6 Nitrogen cycle in sugarcane 138
11.2.7 Biofertilizers 140
11.2.8 Time and method of applying biofertilizers 144
11.2.9 N2 fixers and environmental protection 145
Contents
11.2.10 Ex situ composting of trash and press mud
(modified Japanese method) 145
11.2.11 Vermicomposting 147
11.3 Phosphorus 150
11.3.1 Sources of P 152
11.3.2 Phosphate Solubilising Microorganisms (PSM) 155
11.3.3 Mycorrhizal symbiosis 157
11.4 Potassium 159
11.4.1 Forms of potassium 160
11.4.2 Soil K extractants 162
11.4.3 Source, method and time of K application 163
114.4 Rate of K application and response studies 163
11.4.5 Response to NPK fertilizers 164
11.5 Sulphur 169
11.5.1 Sources of S 171
11.6 Calcium and magnesium 172
11.7 Silicon 173
11.8 Micronutrients 174
11.8.1 Iron and manganese 176
11.8.2 Zinc 176
11.8.3 Other micronutrients 177
11.9 Visual symptoms of nutrient deficiencies and disorders 178
11.10 Nutrition management 180
11.10.1 Soil and tissue testing 180
11.10.2 Crop logging 180
11.10.3 Diagnosis and Recommendations Integrated System (DRIS) 181
11.10.4 Integrated Nutrient Management System (INMS) 182
11.10.5 Constraint analysis 185
11.11 Biological software in sugar industry 186
12. Water management 189
12.1 Evapotranspiration (ET) or consumptive use (CU), Irrigation efficiency (IE), and Water use efficiency (WUE) 190
12.2 Soil moisture status and leaf water potential (YL) 192
mm
Sugarcane in agriculture and industry
12.3 When to irrigate? 194
12.4 How much to irrigate? 195
12.5 How to irrigate? 198
12.5.1 Sprinkler irrigation 198
12.5.2 Furrow method of irrigation 199
12.5.3 Drip or trickle irrigation 201
12.6 Drainage 203
13. Managing the ratoon cane 206
13.1 Ratooning defined 206
13.2 Why ratoons? 206
13.3 The root system in ratoons 207
13.4 Fertilization 209
13.4.1 Nitrogen 209
13.4.2 Phosphorus 214
13.4.2 Potassium 216
13.4.3 Secondary, minor, and beneficial elements 219
13.5 Foliar diagnosis 224
13.6 Time and method of fertilizer application 226
13.7 Yield attributes of ratoon cane 227
13.8 Quality: ratoon vs plant cane 229
13.9 Cultural requirement 229
13.10 Number of ratoons 231
13.11 Ratooning power of cultivars 232
13.12 Water requirement 234
13.13 Gap filling 236
13.14 Trash management 237
13.15 Management of weeds, pests, and diseases associated with ratoons 238
13.16 Effect of growth regulants on sprouting and ratoon yield 238
13.17 Allelopathy in ratoon cropping 240
13.18 Environmental concern: a plea for integrated nutrient management (INM) 242
14. Management of seed cane 249
14.1 Sett treatment 250
14.2 Agronomy of seed cane 250
14.3 Thermotherapy or Heat therapy 251
14.4 Three-tier seed programme 252
15. Integrated weed management 254
15.1 Integrated weed control 256 15.2 Herbicide protectants, antidotes or safeners, surfactants and adjuvants 264
15.3 Weed control in crop rotation and intercropping system 265
15.4 Control of noxious perennial weeds 265
15.5 Methods of application 266
16. Pest and disease management 268
16.1 Pests 268
16.1.1 Shoot borer (Chilo infescatellus Snellen) 269
16.1.2 Top borer (Scirpophaga excerptalis walker) 269
16.1.3 Internode borer (Chilo sacchariphagus indicus.Kapur) 270
16.1.4 Stalk borer (Chilo auricilius, Dudgeon) 270
16.1.5 Gurudaspur borer (Acigona steniellus, Hampson) 271
16.1.6 Root borer (Emmalocera depressella, Swinhoe) 271
16.1.7 White Grubs (Anomala sp., Holotrichia sp., Pentodon sp.,
Alissonotum sp., and Hetronychus sp.) 272
16.1.8 Termites 272
16.1.9 Scale insect: Melanapsis glomerata (Green) 273
16.1.10 Pyrilla (Pyrilla purpusilla, Walker) 274
16.1.11 White files 274
16.1.12 Non-insect pests 275
16.2 Biological control of sugarcane pests 278
16.2.1 Parasites 278
16.3 Diseases 280
16.3.1 Red rot (Colletotrichum falcatum) 281
16.3.2 Smut (Ustilago scitaminea Sydow) 282
Sugarcane in agriculture and industry
16.3.3 Wilt (Cephalosporium sacchari Buller or Fusarium moniliformae Sheldon) 282
16.3.4 Pineapple disease (Ceratocystis paradoxa de Seyner) 283
16.3.5 Leafspots 284
16.3.6 Ratoon Stunting Disease (RSD) (Clavibacter Xyli) 285
16.3.7 Grassy Shoot Disease (GSD) 285
16.3.8 Mosaic 285
16.4 Nematodes 286
17. Transgenic sugarcane: some applications of biotechnology 288
18. Sugarcane simulation models 293
18. 1 Generalia 293
18.2 Empirical models 295
18.3 Mechanistic models. 297
19. Ripening, maturity and harvest 300
19.1 Ripening methods 303
19.2 Methods of cane purchase 307
19.3 Harvest strategy 310
19.3.1 Pre-harvest maturity survey 312
19.3.2 Methods of harvest 312
19.3.3 Mechanised harvesting 314
19.3.4 Post-harvest losses 315
19.4 Cane fires 316
20. jaggery manufacture and allied products 318
20.1 Allied products 323
20.1.1 Khandasari 323
20.1.2 Liquid jaggery (Kaakavi/Kakumbi/Golnupa) 323
20.1.3 Rab 323
20.1.4 Bura 323
20.1.5 Misri 324
20.1.6 Shakkar 324
Contents
20.2 Preservation of sugarcane juice 324
20.3 High fructose syrup (HFS) 324
20.4 Nutrient sweeteners from cane sugar 325
21. By-products of the sugar industry: recent trends 330
21.1 Environmental system 330
21.2 Production system 330
21.3 Economic system 330
21.4 Fibre cane system 333
21.4.1 Factors affecting fibre in cane 333
21.4.2 Role of varieties 334
21.4.3 Bagasse storage 336
21.4.4 Biodegradation of bagasse 337
21.4.5 Development of wet-pile technology 338
21.4.6 Bagasse for paper making 338
21.4.7 Bagasse newsprint (BNP) 338
21.4.8 Agglomerated products of bagasse 340
21.4.9 Other products of bagasse 341
21.5 Energy cane system 346
21.5.1 Efficiency of phytomass production in energy cane 348
21.5.2 Food vs fuel farming 349
21.5.3 Ethanol from fermentable solids 350
21.5.4 Ethanol from cellulosic materials 351
21.5.5 Fuel alcohols 352
21.5.6 Molasses 353
21.5.7 Press mud or filter cake 357
21.5.8 Distillery effluents 359
21.6 Power cane system 360
22. Pollution problems and control measures 362
22.1 Effluent treatment Methods for the sugar industry 362
22.1.1 Physical treatment methods 363
22.1.2 Chemical treatment methods 363
Sugarcane in agriculture and industry
22.1.3 Biological treatment methods 363
22.1.4 Air pollution 367
22.2 Effluent treatment for distillery units 367
22.2.1 General process 368
22.2.2 Anaerobic digestion and methane production 368
22.2.3 Aerobic process 370
22.3 Biocomposting 371
23. Cane farmers and sugar policy 372
23.1 Sugar policy 373
23.2 Enactments 375
23.3 High powered committee recommendations 376
24. Economics of cane cultivation 379
25. Tissue culture 389
25.1 Basic steps in micropropagation 391
25.2 Major advantages of tissue culture 391
25.3 Rapid multiplication of sugarcane by tissue culture 394
25.4 Some terminologies 396
26. What ails the sugar industry? 398
27. Processing of sugarcane into white sugar 399
27.1 Extraction of juice from sugarcane 400
27.1.1 Milling 400
27.1.2 Imbibition 401
27.1.3 Juice weighing 409
27.2 Clarification process 409
27.2.1 Clarification process for manufacturing raw sugar 410
27.2.2 Clarification process for manufacturing white sugar 411
27.2.3 Filtration of sediments 414
Contents
27.3 Evaporation of water 4 l 4
27.3.1 Vapour Bleeding 415
27.3.2 Comments 426
27.3.3 Extraction of non-condensables 427
27.3.4 Condensate extraction 428
27.3.5 Flashing of condensates 428
27.3.6 Syrup sulphitation 428
27.4 Crystallization in vacuum pans (Pan boiling) 428
27.4.1 Cooling of condenser water (injection water) 432
27.5 Crystallisers 432
27.5.1 Reheating 433
27.6 Centrifuging 433
27.6.1 Superheated water wash 435
27.6.2 Molasses separation 435
27.6.3 Magmising 435
27.7 Sugar drying, grading, packing and storing 435
27.7.1 Sugar drying 435
27.7.1 Sugar grading 436
27.7.3 Warehouse 436
Glossary 437
References 438
Appendixes 458
Index 461
Exordium
Sugarcane is a pluriannual plant with a cycle that can last 4-10 years (Fauconnier,
1993). It occupies a unique position in the vertex of cultivated eukaryotes (higher
plants) producing a high biological yield. Perhaps, the plasticity of Saccharum
spp. is their key to success in the acme of evolution. In plant cladistics, it is said
that only the high-sugared ones would survive any aberrance in the ecosystem—
and this giant grass has survived through several millennia. Thus, it has come to
stay as one of the most important crops supporting an agro-based industry in the
world.
Sugarcane is ecofriendly. It alters the microclimate, perhaps reduces CO2 fixa
tion and enhances O2 emission. This plant has been so far regarded as a mono
lithic crop (sugar crop). But it deserves a niche as a multi-product crop providing
food, fuel, fibre, and fertilizer. Thus, though the primary product of sugarcane is
sugar, it also provides biofuel, fibre, and fertilizer, and a myriad by-products be
sides ensuring ecological sustainability (Hunsigi and Singlachar, 1994). Sugar
cane is an important crop of commerce. It ranks sixth in total production among
crops—wheat, corn, rice, barley, soya bean, cane sugar, oats, other food crops
(Moore and Fitch, 1990).
In sugar production, nearly 60% of centrifugal sugar comes from sugarcane
and the rest from sugar beet. Sugar consumption symbolises affluence. But per
capita consumption mirrors geographical and cultural differences. The developed
countries like USA, Australia, Cuba, Brazil consume over 50 kg per capita per
year. But the developing countries of Asia, Africa, and Latin America consume
less sugar. The lowest consumption of sugar of 2 kg per person per year is in the
Central African countries of Burundi and Rwanda. The world average per capita
sugar consumption stands at 20 kg per year. It is difficult to prognosticate the
future pattern of sugar consumption. Increasing health concerns point to an era
of reduced sugar consumption. Reduced sugar consumption is likely in many
countries except, perhaps, Russia and Japan. A substantial reduction in sugar con
sumption is expected due to changes in lifestyle. The reasons attributed are: age
ing population, obesity, cardiac troubles, and fear of being diabetic. Sociologists
warn us that even criminal behaviour is attributed to increased sugar consump
tion. It is reasonably postulated that sugar is neither a devil nor an angel. Hence
'eat sugar with pleasure but with a measure'. The food and nutrition experts ad
vise that except dental caries, sugar consumption has no health hazard. Hence
1
Sugarcane in agriculture and industry
natural sugar provides a cheap source of energy, (one teaspoon releases 18 cal of energy) which is easily digested. What worries health experts is that sugar is always accompanied by fat in sweetmeats—the fat being instrumental in creating innumerable health problems.
In addition to white crystal sugar, low grade non-centrifugal sugars are consumed in Asia, Africa, and Latin America. They are variously called as panela in Venezuela and Columbia, panocha in the Philippines, piloncello in Mexico, chancaca in Peru, and raspadura in Caribbean. In the Indian subcontinent, it is given different names like gur, gula, jaggery, and desi sugar.
Sucrose is a disaccharide, made up of two monosaccharides, namely, glucose and fructose. The empirical formula of sucrose is C12H22O11 with a molecular weight of 343.2 daltons. It is soluble in water and ethanol. Beside being food, it has great potential as an industrial chemical intermediate. Sucrose and sucrose derivatives have been widely used as components of polyurethane resins. A rough estimate indicates that over 65000 tones/annum of sucrose is currently used in the manufacture of polyurethane foam resins.
1.1
TABLE TOP SWEETENERS
Artificial sweeteners have offered a challenge to natural sugar. They are aptly called
'nutritional terrorists'. They are expensive and leave a bitter aftertaste. The oldest
artificial sweetener is saccharin which is 300 times sweeter than natural sugar.
Due to high-tech marketing and advertisement, these sweeteners are gradually
being accepted. The important artificial sweeteners are Aspartame, Acesulfame
K, hydrogenated glucose syrup, Isomalt, Thaumatin, and Zylotol. Of these, As
partame and Acesulfame-K are of great commercial value. The former is 180 times
sweeter than sucrose and is an organic salt. Acesulfame-K is 130 times sweeter
than 4% sugar solution. No bitter aftertaste is noticed. These sweeteners are syn
ergistic and their 'cocktails' (blending 2 or more synergistic sweeteners) are be
coming popular among the elite. Non-saccharide sweetening agents are increas
ingly being used in Japan, USA, Australia, Europe, China, and Brazil (Dwivedi,
1999). The artificial sweetening agents along with their sweetness are given in
Table 1.1. Among the artificial sweeteners, sweet proteins like thaumatin and
monellin are in great demand in many developed countries of the world.
2
1 Exordium
3
T a b l e 1.1 Commercial Non-Saccharide Sweeteners (NSS), intensity of sweetness and consuming countries
Commercial Sweetness NSS consuming products NSS compared to countries
sucrose (on unit wt. basis)
1. Stevoiside 300 Japan, China, Brazil (diterpenoid)
2. Ammoniated 100 USA, worldwide glycyrrhizin triterpenoid
3. Phyllodulcin 400 Japan, Australia, (dihydroisocoumarin) Thailand
4. Thaumatin 10,000 European countries, (protein) Japan, Australia, USA
Source: Dwivedi, 1999.
While it should be conceded that these sweeteners provide 'hollow calories', it can be said that natural sugar from cane/beet will always find a place of prominence. For example, natural cotton, silk, and wool are always preferred to synthetic fibres. The use of High Fructose Corn Syrup (HFCS) in the soft drinks and food industry is dauntingly complex. It is presumed that HFCS will replace at least 10% of the natural sugar market.
Members of the sugarcane family have also found use as fencing, shelter, and building material. Sugarcane plantations serve as windbreaks. Some members are of medicinal value. In some countries the young shoots are eaten as lalab.
1.2
CANE VS BEET SUGAR
The introduction of slavery and peopling of America with blacks is the direct result of sugarcane cultivation.
Sugar beet (Beta vulgaris), a temperate crop, got established during the early part of the 18th century. It was introduced from Europe to USA, and the first beet
Sugarcane in agriculture and industry
process factory was commissioned in 1870, in California (USA). Today, beet sugar contributes 40—44% of the world sugar production. Beet sugar was well-protected for trade at the cost of cane sugar. Several agreements were made to promote international trade of cane sugar. The Lome convention (Lome, capital of Togo) is a unique convention between EEC (European Economic Community), and 46 countries of Africa, the Caribbean, and the Pacific (ACP) which guarantees international trade of 1.37 million tons of sugar. The International Sugar Agreement (ISA) was signed in 1937 but was scrapped due to the outbreak of World War II. The ISA was revived after the war and became effective only from 1 January 1954. Many international agreements such as the US Sugar Act and the Commonwealth Sugar Agreement (CSA) aim at equitable and stable prices for sugar sold in the world free trade market. This also promoted internal consumption of sugar since many countries of Africa and Latin America started producing sugar. Some sugar was also traded under bilateral agreements.
The early part of the 18th century witnessed an era of advancement in factory technology. The vacuum pan was invented by Howard in 1813, and the concept of triple-effect evaporation was conceived and developed during 1830-1860. The centrifugals which provided drier crystals were invented much later. The International Society of Sugarcane Technologists (ISSCT) was formed in 1923 and the first Triennial Conference was held in Hawaii, in 1924. Many ISSCT Congresses were held in different sugarcane growing countries and the 23rd Congress was held in February 1999 in India.
The international sugar trade has been complex and at present 7 8 % of it is for domestic consumption; 15% is sold in the 'free market' with 7% traded under bilateral agreements. It should be emphasised that a fair deal has to be given to a vast section of cane growers.
1.3
ECONOMIC IMPORTANCE
Sugarcane is one of the most valuable global crops with an estimated worth of
US$143 billion (Gallo-Meagher and Irvine, 1996). Worldwide, it occupies an
area of 17 million hectares with a total production of 1076 million tons (FAO,
1996). By the turn of the century, the total production is anticipated to be 1496
million tons. The productivity of sugarcane is highest in Oceania followed by
4
1 Exordium
South America (Table 1.2). The sugar production during 1994 was 110 million tons. The trends of sugar production follow a linear relationship with time,
Y = a + bt,
where t is the time in years, and a, b are constants. By 2010 AD, the expected sugar production in India is about 97 million tons. These figures are much lower than the figures reported by others. Naidu (1989) expected a production of 141 million tons while Kulkarni (1971) expected a value of 150 million tons. The latter seems more realistic. These assumptions will hold if there are no drastic changes in sugar consumption or imbalance in the international trade.
Table 1.2 Area, production of sugar and sugarcane in the world
Continent Sugarcane Production Yield Centrifugal sugar area (million tons) (tons/ha) production (raw (million ha) sugar) (million tons)
World 17.6 1075.89 61.1 109.9
Africa 1.31 69.78 53.2 7.37
North/Central 2.75 152.08 55.2 19.17
America
South America 5.22 355.81 68.1 17.49
Asia 7.87 461.29 58.6 33.57
Oceania 0.44 36.75 83.1 5.50
Source: FAO, 1996.
In the Indian economy, sugar industry plays a vital role for it provides raw materials to over 25 industries. It provides sustenance for over 8 million sugarcane planters. The area under cane is nearly 4 million hectares with a production of about 270 million tons (Box I). There are more than 400 sugar factories in the country with the crushing capacity ranging from 800-10,000 TCD (tons cane per day). The average crushing period ranges from 160-165 days. The average sugar recovery stands at 9.95 to 10.0%. Sugarcane contributes about Rs 800 crores per annum to the central exchequer in excise duties and a further Rs 400 crores
5
Sugarcane in agriculture and industry
per annum to the state governments as purchase tax and cane cess (Mann, 1995).
It also provides direct employment to 400,000 workmen and indirect employ
ment to over 4 million people from rural areas. Thus, the sugar industry is a
source of livelihood for about 35 million people, (ISSCT, 1997). The sugar in
dustry pays annually about US$350 million (present exchange rate US$ 1 = Rs 42)
towards cane price to the planters. Besides, the industry annually spends around
US$100 million towards the construction and maintenance of the feeder roads
and bridges on rivers/canals in the operational areas of the mills. The liquid efflu
ents from the mills are treated by activated sludge method to remove the sus
pended solids and impurities. Apart from this, effluents with a biological oxygen
demand (BOD) of around 30 mgl - 1 after treatment are used for irrigation pur
poses.
There is acute power shortage in the country. The sugar industry has taken a
giant step in the adoption of cogeneration of power. The total cogeneration po
tential of the industry is estimated at 3500 MW (op. cit.). During 1996-97,
surplus power totalling 70 MW was fed to the grid. Surplus bagasse of several
mills is used for the manufacture of cultural paper, newsprint, and particle board.
Our estimates show that 0.37 million tons of bagasse is used exclusively for the
manufacture of newsprint and particle board.
1.4
PRODUCTIVITY OF SUGARCANE
There is hardly any field crop that would exceed the dry matter production of
sugarcane. The production potential of sugarcane (a C4 plant) is very high due to
the distinct anatomical and biochemical features associated with C4 plants. These
include among others, twilight photosynthesis, high specific leaf weight, porosity,
and LAI. Depending on the agro-climatic conditions, the dry matter production
ranges from 20-40 g m - 2 d -1. The ultimate or maximum possible yield of any
crop is unknown. But efforts have been made to estimate the theoretical maxi
mum yield based on incident radiation, quantum efficiency of photosynthesis,
and assumed rate of respiration (Moore, 1989). Moore (1989) has placed the
theoretical maximum yield at 129 g m - 2 d-1, which is equivalent to 1.29 t ha - 1 d-1
or 470 t ha - 1 yr -1. Assuming a photosynthetic efficiency of 3.6%, Naidu (1989)
has calculated a net dry matter production of 198 t ha -1 yr -1 with a biological
6
1 Exordium
Box I
Some highlights of the Indian sugar industry, 1995-96
1. Area under sugarcane 3.93 million ha
2. Cane production 267 million tons
3. Average yield 68.0 tons/ha
4. No. and size of sugar factories 444 (capacity range: 800-
10,000 TCD)
5. Cane crushed by factories 173 millions tons
6. Cane utilised by jaggery/khandsari 70 million tons
7. Crystal sugar production 16.45 million tons
8. Domestic consumption of sugar 13.2 million tons
9. Per capita consumption per year
White sugar 14.1 kg
Gur and Khandsari 8.1 kg
10. Sugar exports 1.0 million tons
11. Projected sugar requirement -2010AD 27-28 million tons
Source: ISSCT, 1996, 1997.
yield of 566 t ha-1 or a cane yield of 339 t ha-1. The theoretical maximum cane yields and recorded yields in peninsular India are presented in Table 1.3. According to Dr. Paroda (1998) there is a wide gap between the potential and existing productivity. The yield gap is 188 t ha -1 in tropical India and 134 t ha-1 in subtropical India. In terms of energy approximately 204 million calories are required to yield 240 million calories, giving an output-input ratio of 1.18. At least ten times energy conversion can possibly be achieved by sugarcane via photosynthesis (Hunsigi, 1998).
7
8
Sugarcane in agriculture and industry
Table 1.3 Theoretical maximum and recorded yields of cane, percentage of sucrose in juice, sugar yield and sugar recovery
Parameters Theoretical Recorded yield maximum yield
Cane yield (t ha-1) 339.0 255.0
Percentage of sucrose in the juice 26.0 22.5
Sugar yield (t ha-1) 55.9 42.0
Sugar recovery 16.47 12.5*
* Average sugar recovery observed in some South Indian sugar factories.
Source: Naidu, 1989.
1.5
SUGARCANE GROWING REGIONS OF INDIA
Basically there are two sugarcane growing regions in India, tropical and subtropical. The tropical region consists of the states of Madhya Pradesh, Maharashtra, Andhra Pradesh, Tamil Nadu, Karnataka, Goa, and Kerala. The subtropical region comprises Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, Assam, and the North Eastern states. In the tropics, ideal weather conditions favour high production and higher sugar recovery. Sugarcane receives 30—36 irrigations. The growth period is quite long, i.e. 10 months or more. The crop cycle ranges from 12—14 months and can extend up to 16—18 months. Bright sunshine and cooler nights favour sugar accumulation leading to higher sugar recoveries. Smut and grassy shoot are the major diseases, while early shoot borers cause extensive damage to cane, particularly the late planted one. Red rot is a serious disease in coastal regions.
In the subtropics, extreme climatic conditions and shorter growth period are the major causes for low yield and lower sugar recoveries. The number of irrigations is restricted to 6—8. Moisture stress during summer, floods, and waterlogging in the monsoon period are factors limiting the yield. Poor cane quality leads to lower sugar recovery. The pest and disease problems are also serious. Red rot and wilt are the major diseases. The top borer and pyrilla are pests of serious concern.
1 Exordium
For the purpose of varietal improvement, the Sugarcane Breeding Institute (SBI)
has recognised seven agro-climatic zones, 4 in the subtropical belt and 3 in the
tropical region. However, for practical purposes, 5 sugarcane growing zones have
been identified.
1. North Western Zone Haryana, Punjab, and Western Uttar Pradesh
2. North Central Zone Eastern Uttar Pradesh, Bihar, and West Bengal
3. North Eastern Zone Assam and other North Eastern States
4. East Costal Zone Coastal Tamil Nadu, Coastal Andhra Pradesh, and Orissa
5. Peninsular Zone: Maharashtra, Madhya Pradesh, Gujarat, Karnataka, Tamil Nadu (barring coastal area), Kerala, and inte
rior Andhra Pradesh and Tamil Nadu
The tropical region contributes about 40% of the total cane production in the
country.
Srivastava et al. (1988) have delineated the efficient zones of production. Ac
cording to them Zone-I is of high yield and high spread. The Zone-II is high yield
and low spread. The Zone-Ill is low yield with high spread. Judging by these
parameters, parts of western Uttar Pradesh, Haryana, Maharashtra, Andhra Pradesh,
coastal areas of Tamil Nadu, and Assam have high yield accompanied by high
spread. Most of the areas of Uttar Pradesh, Bihar, and Punjab have low yield and
high spread. The rest of the area in the country has relatively high yield and low
spread (op. cit.).
A priori, fertilizers, cultural practices and good seed contribute 65% towards
cane production. Varieties play an important role and contribute 20%, while irri
gation contributes 15% towards cane production.
Analysis of the yield gap has been carried out by Arulraj (1995). The yield gap
depends on the soil type and management practices—the highest yield gap of 68—
69% was observed in Madhya Pradesh and Uttar Pradesh, while it was as low as
3 1 % in Punjab. In general, on an all-India basis, the sugarcane yield gap is around
50% (Table 1.4). This can be reduced to achieve the sugarcane requirement of the
country, i.e. 300 million tons of cane by the turn of the century.
9
Sugarcane in agriculture and industry
Tab le 1.4 Yield gaps in different states
Potential Existing Yield gap States productivity productivity (%)
(t ha-1) (t ha-1)
1. Andhra Pradesh 169.01 72.1 57.34
2. Bihar 97.16 45.4 53.27
3. Gujarat 139.77 85.5 38.83
4. Haryana 111.21 48.9 56.03
5. Karnataka 150.00 86.0 42.67
6. Madhya Pradesh 107.25 33.4 68.86
7. Maharashtra 182.33 76.4 58.10
8. Orissa 108.70 64.6 40.57
9. Punjab 82.60 56.7 31.36
10. Tamil Nadu 193.70 104.0 46.31
11. Uttar Pradesh 172.72 55.4 67.92
12. West Bengal 105.07 57.7 45.08
Source: Arulraj, 1995.
1.6
NON-SACCHARIFEROUS PLANTS
Among field crops, sugarcane, sugar beet, and sweet sorghum are sacchariferous plants. It is estimated that by 2025-2030, the world's requirement of sweeteners will be around 250 million tons. India's requirement will be about 40 million tons (Dwivedi, 1999). Sacchariferous plants alone may not be able to meet the huge global demand of sweeteners. Sweeteners from non-sacchariferous plants could help fill the gap. The sweet principle in these plants is 100-10,000 times sweeter than sucrose on a unit weight basis. These natural sweetening agents have a low calorific value as compared to sucrose (3600-4000 cal g-1). The sweet principle in these plants is in leaves, roots, shoots, fruits, etc. and comprises terpenoids, ster-
10
1 Exordium
oids, steroidal sponins, dihydrochalcones, dihydroisocoumarins, proteins, etc. The natural sweetening agents from non-sacchariferous plants are increasingly being used in developed countries like Japan, USA, Australia, and those in Europe.
At present, 15 species of non-sacchariferous plants have been identified. India is the natural habitat for as many as 13 species (loc. cit.). The important ones are: Perrillafrutescens, Stevia rebaudiana, Glycyrrhiza glabra, Abrus precatorius, andAchras sapota. The sweet principle of these species is 100 to 2000 times sweeter than sucrose. It is stated that Abrus precatorius is a substitute for Glycyrrhiza glabra. Some important sweet species, the active principle, and the parts containing it along with the method of propagation are presented in Table 1.5. There are also shrubs and woody trees like Hydrangea macropkylla, Smilax glycyphilla, Symplococos paniculata, and many citrus species which produce sweetening agents. In fact, Symplococos paniculata is well-known as sweet leaf and the principle Trilobatin is 400—1000 times sweeter than sucrose. There are also super sweet trees/shrubs grown in the tropical/subtropical regions of India.
There are sweet inducer plants such as Cynara scolymus L (Compositae). It is propagated by seeds/suckers/offshoots. The sweet principles present in the leaves are cynarin, chlorogenic acid, and caffeic acid. Dwivedi (1999) argues that 0.1 million hectares under non-sacchariferous plants is enough to meet the national requirement of sweetening agents as against the vast cultivable area required for sugarcane. However, this author asserts that the propagation and culture of these plants are difficult for widespread adoption. Hence, these non-sacchariferous plants, though highly beneficial and ecofriendly, have remained in the backyard and may not achieve a stage of commercial exploitation in the near future.
11
Sugarcane in agriculture and industry
12
13
1 Exordium
Origin, history, and distribution
Sugarcane has held the attention of many, from monks to monarchs. Legend has
it that Gautama, who became Lord Buddha, was born of sugarcane. The first
offerings to Lord Buddha were 'sticks of sugarcane'. Alexander the Great, during
his invasion of India noted that this 'honey reed' was a closely spaced, well-
husbanded garden crop. It is also related to Indian mythology in many ways. The
wild species Saccbarum locally called as Kans is used in many rituals. Saccharum
spontaneum has a mention in Valmiki's Ramayana. The plant was used in cloning
and culturing of a new child in the place of the lost child 'Lava' (son of Goddess
Sita). The earliest reference to sugarcane is in Atharva veda and Rig veda (10000—
5000 BC). Cane planting was well established in the Indus valley. The term sarkara
for sugar is known only in the Hindu scriptures. Sugar does not find a mention in
the Holy Quran, the Holy Bible or the Talmud (the Jewish Holy scriptures). It
can be reasonably postulated that the Indians knew the art and science of sugar
making. It is believed that sugar was made in India in 3000 BC. Saccharum seems
to originate from the Sanskrit word Sarkara.
Derr (1948) has extensively delved into sugarcane in Indian mythology. It is
suggestive of prosperity, for the Goddess of Wealth holds the stick of a well-grown
sugarcane. According to the inhabitants of Solomon Islands, mankind seems to
originate from the cane variety tohononu. Derr (1948) provides evidence that ba
gasse was used as fuel in India in AD 100.
Sugar and sugarcane have been highly prized since pre-historic times. Sugar
cane has spread to more than 79 countries between the latitudes, 36.7° N and
31.0° S. Figure 2.1 shows the global distribution of sugarcane. It is worth noting
that the perennial grass is concentrated in the tropical and subtropical regions of
the globe. However, in the regions lying between 18° North and South of the
equator, sugar accumulation is much higher—these regions can be said to make
up a sugar bowl.
The origin of sugarcane is controversial, but the West as the original home is
ruled out. It seems reasonable that the cultivated canes originated in the south Pa
cific, that is, to the east of 'Wallece's line' (Alexander, 1973). It has been suggested
that there was a continuous 'land bridge' between the gigantic Asian and Austral
ian continents during the Cretaceous period, which assisted the spread of canes to
Melanesia.
14
2 Origin, history and distribution
Fig. 2.1 Sugarcane growing areas of the world
The geographical distribution was widespread and, sugarcane was established as a domestic crop in 8000 BC by Neolithic horticulturists in New Guinea. From there, it went to China and India and to the Pacific Islands. The thin canes of India (S. barberi) was found in 6000 BC and the Persians brought these canes to the Mediterranean around 500 BC. The Arabs are credited with establishing the cane in Morocco in the 8th century AD. Sugar refining was perfected by Egyptians.
From Spain sugarcane spread to the Canary Islands and west Africa. The Spaniards and Portuguese were responsible for the spread of cane culture in the New World during the 16th century. On his second voyage in 1493, Columbus introduced cane to Santo Domingo, now the Dominican Republic. By the 17th century, it spread to the sugar isles of the Caribbean and from there to the Latin American countries including Brazil, Mexico, and Peru. Independent of the Western movement, scientific cane culture was practised in Mauritius, Reunion, Australia, Fiji, and South Africa (Irvine, 1977).
15
Related species and genera
RELATED SPECIES AND GENERAL DESCRIPTION
The species recognised in addition to S. officinarum (2n = 80) include S. spontaneum (2n = 40-128), S. barbari (2n = 82-124). S. sinense (2n = 88), S. robustum (2n = 60—194), S. sanguineum (2n = 60), and S. edule (2n = 80). But S. edule can hardly be called as sugarcane. It has aborted inflorescence and is eaten by natives of Melanesia. S. edule originated in New Guinea by natural hybridization between S. robustum and Miscanthus floridulus. These are low in sucrose and high in fibre content. However, Purseglove (1988) considered that S. edule is probably the sterile form of S. robustum. The recognised 5 species are: S. spontaneum, S. robustum, S. sinense, S. barbari, and S. officinarum. According to Parthasarathy (1948) cultivated sugarcanes belong to two main groups: (a) thin and hardy canes of North India, botanically classified as S. barbari and S. sinense and (b) thick noble canes, S. officinarum.
The saccharum complex consists of all six species of Saccharum, and the genera like Narenga, Erianthus, Miscanthus, and Sclerostachya. Mukherjee (1957) opines that Sclerostachya and Narenga should be considered more primitive than Erianthus but Saccharum is more advanced than any of the related genera. The area of origin of this complex is Indo-China-Myanmar border (Roach and Daniels, 1987).
(1) Saccharum spontaneum. It is an extremely variable species with high ploidy (2n =
40-128), occurring in the wild from Africa to the Middle East, China, Malaysia
through the Pacific to New Guinea. It occurs in the wild, preferring the habit of
swamps and marshy places, but occurs in the uplands as well. It originated probably
in the colder regions of tropical India. It is a perennial grass, free tillering with
robust rhizomes, and its leaves are upto 200 cm long with variable width. Sheath is
persistent with high fibre and low in sugar. Panje (1933) recognised two sub-spe
cies, namely, indicum and aegypticum. S. spontaneum has contributed the most to
wards the development of modern cultivars by offering resistance to most of the
major diseases and providing vigour and hardiness.
16
3.1
3 Related species and genera
(2) Saccharum robustum. It originated in New Guinea. Its growth is very vigorous and luxuriant; it attains a height of 10 m. The stems are of medium girth, and have high fibre and low sugar content. It grows along river banks. The stems are hard, woody, and have pithy centres with little juice. It is susceptible to Fiji disease, mosaic viruses, leaf scald, downy mildew, and root rot. Hence, it is not extensively used in breeding programmes. A sub-species of S. robustum is recognised, i.e. sanguineum. Brandes and Sartoris (1936) reiterate that the 'cradle of cultivated sugarcanes' is the region where the two wild species, namely, S. spontaneum and S. robustum are found.
(3) Saccharum barbari. It is a small group indigenous to North India and suited to subtropical and temperate regions. Based on vegetative characteristics, Barber classed them into 4 groups, namely, Mungo, Nargori, Saretha, and Sunnabile. Among these, the most important one is Saretha which has contributed to the development of noble cane Co 213 and PoJ 213. The Saretha group is well represented by Chunee canes and has produced a number of useful hybrids. The clones of S. barbari are short, medium to short in thickness with high fibre content, medium sucrose content and poor yields. But it tillers abundantly which is a useful trait in breeding of cultigens.
(4) Saccharum sinense. This is a native of China and is well represented by the
Pansahi group. The clones are tall, hardy, and vigorous with wide adaptability,
and early maturity. The stems are slender with high fibre content and poor juice
quality. The leaves are broader than those of S. barbari. The variety Uba spread
worldwide due to is frost resistance and immunity to gummosis, mosaic, and
sereh diseases. It is however, susceptible to red rot and rust. It was later replaced by
noble canes with better yield potential and juice quality.
(5) Saccharum officinarum. It is a noble cane, distinctly thick and juicy. It is supe
rior in quality with less fibre. S. officinarum does not occur in the wild. Its origin
has been contentious but sufficient evidence suggests that it is a native of the
Indo-China-Myanmar border with New Guinea as a prime centre of diversity.
The probable putative ancestor is S. robustum with introgression from Erianthus
maximus. The genetic origins of Saccharum sp. are presented in Fig. 3.1. The
clones have a bewildering range of local names with an astonishing assortment of
colours (Purseglove, 1988). Some important noble canes which are in commer
17
Sugarcane in agriculture and industry
cial cultivation are Tahiti, Otaheite, Bourbon, Blanche, Lahaina, Vellai, etc. The noble cane 'Cheribon' originated in Java and is also known as light Cheribon, black Cheribon, or stripe Cheribon. In the account of Caption Cook's voyages there is a reference to the cultivation of 'Calodina' in New Hebrides. A prominent noble cane 'Badila was in cultivation for long in South East Asia and Oceania.
Fig. 3.1 Genetic origins of Saccharum sp. (Source: Fauconnier, 1993.)
S. officinarum is suited to tropical conditions and requires favourable soil and climatic conditions, and careful husbandry. The stems are stout, thick, high in sucrose, low in fibre, and have a soft rind—hence, they are also the chewing canes. But the noble canes are highly susceptible to all major diseases.
With the march of human civilization, sugarcane has evolved from a garden crop for chewing purposes to being used for making syrup and jaggery and later crystal sugar—it has got established as an important industrial crop of the world. By 1925, the noble canes (S. officinarum) were out of cultivation as they were highly susceptible to major diseases. Now the complex hybrids of Saccharum sp. are bring used in commercial cultivation to suit the different agro-ecological regions of the world. The future will witness an era of transgenic plants with multiple resistance to pests, diseases, herbicides, etc. and with augmented yield, sugar output and value-added products. The evolution of sugarcane {Saccharum) as outlined by Simmonds (1976) is presented in Fig. 3.2.
18
3 Related species and genera
19
Sugarcane in agriculture and industry
3.2
NOBILIZATI0N PRODUCTS
The process of nobilization in sugarcane is modified back crossing. The word
'nobilization' means the crossing of wild cane, S. spontaneum with S. officinarum
and repeat back crossing with the noble parent, i.e. S. officinarum. Nobilization
means the ennobling of the wild species with thick stalks and good quality. Re
cendy, Mudge et al. (1996) have presented the genetic map of Saccharum officinarum
which contributes 90% of the genomic composition in commercial clones. Of
secondary importance is S. spontaneum which contributes approximately 5-10%
of genomes to commercial cultivars. The female parent is S. officinarum and S.
spontaneum is the male parent.
In back crossing, doubling of chromosomes occurs in the noble parent and the
progeny inherits 2n chromosomes from S. officinarum and n chromosomes from
the wild species S. spontaneum. The result is progeny with 3n chromosomes. Thus,
most of the commercial varieties are derived from S. officinarum x S. spontaneum
and are high polyploids (aneuploids). On record, the greatest of all nobilized prod
ucts is PoJ 2878 which ruled the 'sugar world' for a long time and earned the
sobriquet 'wonder cane'. From then on, a large number of interspecific hybrids
have been released which outclassed each other. But in the long history of sugar
cane culture, there has been a continuous procession of varieties which on com
mercial cultivation for some time become extinct. This is termed as 'runout' of
varieties or yield decline.
Varietal yield decline is a syndrome, the causes of which are unknown. A ruling
variety after some years of commercial cultivation loses its vigour and yielding
ability. Humbert (1959) asserted that the yield decline is due to a number of biotic
and abiotic stresses. Lack of aeration, high soil bulk density, and accumulation of
toxic elements are some of the factors causing yield decline. Reduced O2 supply
restricts root proliferation causing runout of varieties. Similarly, soil erosion, re
duced availability of trace elements, loss of organic matter due to oxidation in
tropics, and poor drainage with anaerobic conditions for long periods of growth
can cause the varietal yield decline. Poor management and gradual build-up of
pests and diseases can cause decline in yield of many commercial cultivars. Dis
eases like ratoon stunting (RSD), mosaic, red rot, root rot, etc. are instrumental in
20
3 Related species and genera
varietal yield decline. The chief causal agent for this malady is the pink mealy bug (Saccharicoccus sacchari) which carries a viral vector. Many major varieties like Co 419, Co 740, Co 421 are showing various shades of yield decline. Profusely flowering canes show early yield decline as compared to shy or non-flowering canes. Typical symptoms of yield decline are (a) premature drying of older leaves, (b) stunted growth, reduced height and girth, (c) only top 5-6 leaves remain green, and (d) a gradual tapering of the apex. Since sugarcane is vegetatively propagated, genetic deterioration of cultigens is ruled out. It is reasonably argued that heat therapy, good husbandry, and judicious use of organics and inorganics including micronutrients would greatly contain the varietal yield decline. Replacement by superior genotypes leads to a fairly permanent solution.
i 21
Botany of sugarcane
The taxonomic classification of sugarcane is that the genus Saccharum belongs to the family Poaceae (Graminae), sub-family Panicoideae, tribe Andripogoneae, and sub-tribe Saccharininae. According to Heinz (1987), the sub-tribe has two natural groupings, namely, Saccharastrae and Eulaliastrae which are not, however, the formal taxonomic units.
Fig. 4 .1 Stem of sugarcane
An elegant treatment of the botany of sugarcane is given by Van Dillewijn
(1952). The basic structure of cane is like any tropical grass. The economic part is
the culm—the stem/stalk. The stem is unbranched, circular or oval in cross-sec
<J9MNWMKBa«HeMM»<>>».
22
4 Botany of sugarcane
tion. It is differentiated into joints, each comprising a node and internode. The node consists of a lateral bud, a band of root primordia, and a growth ring (Fig. 4.1). Sugarcane is propagated asexually by stem cuttings or setts having 1-3 buds. Nodes are very close to each other at the base and top portions. The basal portion, due to closeness of buds, assists in the formation of shoots or tillers and multiple cuts (ratoons). The buds vary in size and shape and may be oval, rounded, triangular, etc. These variations help in distinguishing the varieties. The internodes vary in length from 5—25 cm and in girth from 1.5—6.0 cm in diameter. Sugar accumulates in the internodal region and the long internode is a characteristic feature of quality cane. A well-ripened cane gives a metallic sound when tapped. Moisture stress leads to shortening of internodes. At maturity, each stem may have 25-30 internodes. The cross-section of the stalk/stem could be cylindrical, conoidal, barrel, circular or oval. The stem can be striped, yellow, green, purple or variegated. The colour of the stem is controlled by the environment and modified by a coating of epidermal wax. Stem colour should not be used as a diagnostic tool or identifying varieties. The surface of the internode, save the growth ring is coated with wax. The wax coating consists of densely crowded tiny threads or rods (Van Dillewijn, 1952) and is conspicuous in the upper section of the internode where it forms a wax ring (Fig. 4.1). In some varieties, a pronounced depression or the vertical channel known as bud groove or bud furrow is prominent. At the nodal region, a root band is present with rows of root primordia which give rise to sett roots. Just below the stem epidermis, a narrow cortex or rind is observed. The rind is made up of cortical cells; many of them are sclerenchymatous. Rind hardness is of practical importance at both the field and factory levels. At the field level, a hard rind gives protection against rodents, jackals, pigs, rabbits, etc. At the factory level, rind hardness leads to 'slippage' and reduced juice extraction. Rind hardness depends mostly on the varieties and external factors like irrigation. It is generally observed that the rind is relatively softer in noble canes and varieties grown under irrigation, as compared to commercial hybrids and non-irrigated canes. Rind hardness is measured by an instrument, which works on the same principle as that of 'presometer' (Van Dillewijn, 1952). As reported by Van Dillewijn (op. cit.), the softest cane has a rind hardness of 1.4 kg, tropical canes 1.8-2.7 kg, and the North Indian canes 3.18—3.60 kg. The hard rinded canes have a hardness of 3.6-4.09 kg, whilst the wild cane Saccharum spontaneum has a hardness of 4.5 kg. Lakshmikanthan (1983) has presented snapping stress to suggest rind hardness in cultivated species. Quoting other sources, Van Dillewijn
23
Sugarcane in agriculture and industry
(1952) indicated that rind hardness is associated with the distribution of vascular bundles, the number and size of sclerenchymatous cells and their lignification.
The leaves are the important functional parts. They are attached to the stem at the base of the nodes, alternately in two rows on opposite sides of the stem. Each leaf consists of a sheath and a blade separated by a blade joint, i.e. the dew lap or collar. The sheath is a tubular structure with a broad base and tapering end. The sheath is an important diagnostic tool, and in some varieties, the sheath is closely attached, while in others it is detrashing or free trashing. It protects the buds and the self-detrashing varieties are preferred as clean cane can then be supplied to the factories. A membraneous appendage of the sheath called ligule separates it from the leaf blade. The ligule can be used as a distinguishing characteristic between varieties. The sheath may be smooth or covered with spiny hairs. A projection from the leaf sheath near the blade joint (dew lap) is the auricle (ear shaped) which may not occur in all varieties. A fully grown leaf may be as long as 60-150 cm, with a width of 2-10 cm. A well-grown crop can have a leaf area 8-10 times the ground area at grand growth phase.
In sugarcane, two types of roots are distinguishable, namely, sett roots and shoot roots (Fig. 4.2). As the sett is planted in well-tilled moist soil, sett roots strike from the root primordia of the seed piece. These roots are thin, branched, and transient. With the formation of the shoots, shoot roots are formed, which perform the main function of absorption of water and nutrients, and provide anchorage. With the formation of shoot roots, sett roots cease functioning and die (Fig. 4.2). Each shoot produces its own root system. Hence, tillering parallels the shoot root formation; as the tillering stops root formation also ceases. Shoot roots are thicker and whitish in colour.
Evans (1935) has described three types of roots: superficial roots, buttress roots, and the rope system. The superficial roots absorb water and nutrients; the buttress roots provide anchorage; and in the rope system, the roots can penetrate to a depth of 3—6 m is search of moisture and fight drought. This author has observed stubble roots to a depth of 1.5 m after the cane was harvested and ratoons are raised. The stubble roots of ratoons are suberized, thick, dark in colour, and less efficient in absorbing water and nutrients (Hunsigi, 1993).
The inflorescence of sugarcane is known as arrow or tassel. At maturity, and proper photoperiod, the terminal meristem is transformed into inflorescence primordium. The first sign of flowering is successive sheaths becoming longer and the blades shorter. Eventually, a small leaf (SL) or flag leaf is formed with a young
24
4 Botany of sugarcane
Fig. 4 .2 Root system in sugarcane
panicle of 90 cm length being pushed out. The inflorescence is a branched panicle and the cultivars can be identified based on the size, shape, and colour of the arrow. The branched panicle has hundreds of tiny flowers. These appear in pairs (spikelets), one without stalks (sessile), and others attached to stalks (pedicillate). Some flowers may have fertile pollen and eggs. On pollination, seeds are formed— dry one-seeded fruits or caryopses. The seeds are ovate, yellowish brown, and very small (1 mm long). The seed has a short viability but can be stored in a desiccator for two weeks. The tiny seeds are placed on the surface of shallow trays and they germinate better in light. Germination takes place in 2-5 days and transplants are ready after six weeks.
Sugarcane has 4 distinct phases in its life cycle: (a) germination and emergence, (b) tillering and canopy development, (c) grand growth, and (d) maturation, including flowering and ripening. The first phase takes about 4—6 weeks depending on the agroclimatic conditions. The vegetative phase comprises tillering and stalk elongation and is accompanied by increased dry matter production. The transformation from the vegetative to the reproductive phase is not distinct.
25
Physiology of sugarcane
Sugarcane has a long growing season, high water requirement, some salt and
drought tolerance, but little cold tolerance. It responds well to high fertility, irri
gation, drainage, and abundant sunlight (Irvine, 1983). Being a C4 plant, it has
a h i g h p h o t o s y n t h e t i c rate (Pn) r a n g i n g from 47 mg d m - 2 h - 1 to
100 mg d m - 2 h - 1 (op. cit.). The principal external factors which influence
photosynthesis are light spectral quality and intensity, the CO2 concentration
in air, temperature, moisture, and nutrition. A four-fold increase in photo
synthesis is observed when the CO2 concentration in air is increased from
0.01%-0.06%, but saturation occurs at 0.06%. Similarly, a linear increase in
Pn is noticed when the light intensity is increased from 300-600 cal/cm2/d.
Photosynthetic rates are higher in the blue spectrum (480 nm) than in the red
spectrum (620-695 nm). The Saccharum spp. have different Pn rates: S. spon
taneum 51.4 mg d m - 2 h - 1 , S. officinarum 29.7 mg d m - 2 h - 1 and interspecific hy
brids 36.0 mg dm - 2 h - 1. The overall average photosynthetic rate is 47 mg d m - 2 h - 1 .
In general, photosynthesis is influenced by leaf width, specific leaf weight, and leaf
porosity. Thicker leaves have higher concentrations of N, P, and K, which
accounts for the higher Pn rate. T h e accumulation of sucrose in the leaf may
inhibit photosynthesis, probably due to product repression. Photosynthetic rates
have a marginal influence on the yield. The yield is determined by stalk density,
stalk length, and stalk weight.
Recent investigations by Nose et al. (1995) indicate that photosynthetic rates
are influenced by the activities of phosphoenol pyruvate carboxylase (PEPC), malic
enzyme (ME), soluble protein (SP), fraction-1-protein, chlorophyll, and N con
tent. More importantly, photosynthetic carbon exchange rates (PCER) at high light
intensities (2000 μE m i - 1 s-1) contribute to canopy photosynthesis. In feral (wild
canes) sugarcanes PCER ranges from 20.46 to 81.56 mg C d m - 2 h - 1 . In C4 plants,
carbon exchange rates are higher than 50 mg CO2 d m - 2 h - 1 and are affected by
high light intensities, stomatal apertures, and metabolic events in leaves. The au
thors infer that the potential productivity of sugarcane is decided by the product
of the leaf area and photosynthetic efficiency. It, therefore, appears that
S. spontaneum can be used to improve photosynthetic efficiency from 1.3 to 1.6%.
This is relatively less in ratoons.
Photosynthetic rates influence dry matter accumulation and crop growth rate.
Irvine (1983) has reported a dry matter yield of 84 t ha - 1 yr - 1 while this author has
observed an average dry matter yield of 60 t ha - 1 yr - 1. Irvine (1983) has reported
26
5 Physiology of sugarcane
that a crop of 163 t ha -1 of millable cane would have a cumulative respiratory loss of 42 t ha -1 . Some physiologic parameters of cane cultivars grown in alfisols of peninsular India are given in Table 5.1 (Hunsigi et al., 1975). The crop growth rates have varied from about 20 to 52 g wk -1 in different cultivars. Stalk elongation is minimal during tillering phase (~3 months) but maximum rates range from 2.3 to 2.5 cm d -1
Ambient temperatures lower than 15—17 °C drastically reduce stalk elongation.
Leaf area and Leaf Area Index (LAI) are important growth components which influence dry matter production and eventually the cane yield. Maximum yield can be obtained from cultivars that combine high LAI with erect leaves. However, LAI is a function of plant density and dense stand/close spacing results in higher LAI. A vigorous stalk will carry about 10 green leaves with leaf surface area of 40,000 m2 and LAI of 4. The LAI values in sugarcane range from 2 to 8 and 4 . 0 -5.0 seems to be the optimum, during the grand growth phase. The optimum LAI is the one which intercepts 95% light. Ratoons may have an optimum LAI of 3-4 during the rapid close-in period. A positive and strong correlation between LAI and dry matter yield has already been alluded to. It is reasonable to assume that the maximum LAI would be about 8.0.
In 'truck crops' like sugarcane, potato, tapioca, sugarbeet, etc. where the vegetative portion is the economic produce, Harvest Index (HI) is a crude criterion to explain the physiological processes. In these crops, partitioning is continuous and is not amenable to agronomic manipulation to increase yield. Nevertheless, crops with vegetative sinks need to obtain maximum partitioning to harvestable product.
Narrating historical changes in HI , Sinclaire (1998) stated that it represents migration coefficient of photosynthate. Improvements in HI emphasise the importance of carbon allocation to economic produce. He has attributed close association between HI and N accumulation in plants. A crop with high HI requires a concomitant increase in crop N accumulation. Hence, nitrogen harvest index H I N
(ratio of N in economic produce to the total amount of N in plant) is envisioned to rationalise the HI values. It is presumed that H I N values in sugarcane should be aimed above 0.5.
To sum up, the HI of sugarcane is ~ 0 . 6 and that of potatoes is ~ 0 . 8 7 , where the economic produce is millable canes and tubers respectively. In sugarcane, when sugar is taken as the economic produce, the HI comes to 0.2; if all sugars including molasses are taken, the HI becomes 0 .23-0 .25 . When all the co-products and by-products of cane are taken including the cogeneration of power from bagasse, the HI reaches nearly unity.
27
Sugarcane in agriculture and industry
28
5 Physiology of sugarcane
5.1
SUCROSE: THE MAIN CURRENCY
Sucrose is the chief currency of all higher plants, particularly, of sugarcane. It also acts as an active messenger conveying information on the energy status of individual tissues. Sucrose is synthesised in the cytoplasm of photosynthetic cells from where it can be exported to the vacuole and the cell-wall. The most common enzyme which hydrolyses sucrose is invertase. It is present in the central vacuole and in the cell-wall. Invertase is considered a biofunctional enzyme, both catalysing sucrose breakdown and indicating the carbon status.
Sucrose is exported in the phloem. The very fact that sucrose and invertase coexist in an uneasy alliance, suggests continuous synthesis and breakdown. Paradoxically, hexoses in the vacuole, more so the fructose will inhibit invertase activity and slow down its action.
Lingle (1997) observed that sucrose begins to accumulate in cane internodes when they start elongating and continues until elongation ceases. In elongating internodes much of free sugars are glucose and fructose. Nonetheless, total sugar concentration continues to increase almost linearly as the heat units range from 400-600 °C d. On the other hand, the heat units required for phyllochron (leaf appearance rate) varies from 75.2 to 81.3 °C d (ibid.).
A significant correlation between the activity of Sucrose Synthase (SS) and sugar accumulation implicates its positive role in sucrose synthesis. Sinclaire (1997) maintained that SS activity is a measure of sink strength in plants. Two sucrose synthase isozymes, SSl, and SS2 have been identified in sugarcane.
The primary enzymes of sucrose metabolism in plans are invertase enzyme commission and sucrose phosphate synthase. But it is believed that sucrose cleavage is associated more with the activity of acid invertase. The activity of neutral invertase is highly variable among internodes. This is further corroborated by the experiments on glyphosate [N-(phosphoromethyl) glycine] used as a ripener. This chemical reduces the growth of the apical meristem and the activity of acid invertase. In addition, the water content of developed internodes decreased from about 900 to 720 g kg-1. Late formed internodes reached low water content in less heat units than did early formed internodes.
Lingle (loc. cit.) concluded that sugar-rich harvest is accompanied with low soil N availability, low soil moisture status, and cool temperatures.
29
Varieties in sugarcane
Varieties in sugarcane are called 'holy cows' for they are to be tended, maintained,
and propagated. As they are vegetatively propagated, the admixtures in commer
cial plantations are a common observance. A varietal spectrum consisting of short
duration, early and midlate varieties are of prime importance to get a higher sugar
recovery with an extended crushing period. In tropical India, the grinding or
crushing period may range from 240-300 days with a season's average recovery of
10.0 to 11.0 per cent. The ratoons and early maturing canes are crushed at the
beginning of the season. This is followed by midlate, and if needed late varieties
can be taken for crushing before the end of the season. Thus a varietal spectrum
ensures a flattened curve with high sugar recovery as against a highly skewed curve
of a single varietal crush (Fig. 6.1). A single variety, multiplied, and maintained by
one sugar factory may be subjected to endemic pests and diseases which might
take an epic scale. Thus, as a consequence, the single ruling variety may be wiped
out, and it takes a couple of years to develop and multiply the seeds on a commer
cial scale. It is worth noting that the seed ratio in sugarcane is very low, i.e. 1 : 1 0
or 1 : 12 (one hectare of seed cane provides for 10 to 12 ha of planting material).
A rational blend of varieties is as shown below:
(a) Early rich canes, short duration cvs and ratoons 40 per cent
(b) Midlate cvs 50 per cent
(c) Late and other miscellaneous cvs 10 per cent
Total 100 per cent
This is however, a rough guide and the cane managers should aim to maintain 5-
6 cultigens of varying maturity. Nonetheless, it is essential to keep 2—3 cvs in the
pipeline.
Since 1950 more than 100 varieties have been released in India for commercial
cultivation. During the early period of the 19th century, noble canes were under
cultivation. These included Otaheite, Cheribon (Creole), Caledonia (Malabar),
Badila, etc. But the noble cane era came to an end by 1925 due to serious diseases
like mosaic, sereh, smut, and red rot. The disease attack was on an epic scale and
it practically wiped out these noble canes. This also heralded the development of
nobilized hybrids. The first hybrid developed was PoJ 2878 (PoJ 2364 x EK 28)
which earned the sobriquet—the wonder cane. Other important hybrids include
30
6 Varieties of sugarcane
Co 419 (PoJ 2878 x Co 290) and Co 740 (P 3247 x P 4745) which are under cultivation for over four decades. The tonnage variety is Co 62175 (Co 915 x Co 419) which yields more than 180 t ha-1 in peninsular India. Similarly Co 421 had occupied large areas in Central and Eastern Africa. Other exotic strains which deserve recognition are B 37172, B 62163, NCO 310, CB 41-76, CP 65-357, PR 980, F. 160, and Q 69. The salient features of some important varieties grown in India are given below (Sankarnarayana, et al., 1986).
Fig. 6.1 Effect of varietal spectrum on sugar recovery and crushing period (Schematic)
(1) Co 853 (Co 508 x Co 617). Medium thick cane, purple colour, splits common, midlate, good juice quality, withstands waterlogging and drought, moderate resistance to smut. Good ratooner, jaggery is of light yellow colour, crystalline, hard in consistency, and of good quality. Profuse flowering. The yield potential is 140 t ha-1, with 17-18% pol. The CCS yield was about 18 t ha-1.
31
Sugarcane in agriculture and industry
(2) Co 1148 (P 4383 x Co 301). Grows in the subtropical belt and occupies nearly
60% of the area in Uttar Pradesh. In Haryana and Punjab, it occupies nearly 2 5 %
of the area. Good ratooner. Its yield potential is about 60 t ha -1 with 17—18%
sucrose. Medium thick with hard rind, midlate to late in maturity. Resistant to
red rot.
(3) Co 1158 (Co 421 x Co 419). Medium thick erect cane popular in the sub
tropical belt. Its spread is next to Co 1148 in Uttar Pradesh, Bihar, Punjab, and
Haryana. It yields about 75 t ha -1 with 15-16% sucrose. Moderately resistant to
red rot and wilt, and tolerant to drought conditions. Midlate variety and a good
ratooner.
(4) Co 62175 (Co 951 x Co 419). Thick cane and the yield potential is over
200 t ha -1. Moderate juice quality. Eye buds are prominent with a tendency to
sprout in situ. It is a popular variety in Karnataka, Andhra Pradesh, and Mahar
ashtra. It has a waxy coating and the rind is relatively soft. Less susceptible to
smut, red rot, and helminthosporium. Midlate variety and matures in 13 months
with 18-19% sucrose. It is a vigorous and good ratooner.
(5) Co 62198 (Co 34—120 x Co 775). Medium thick and erect cane with green
colour mixed with a tinge of purple. Bud is plumpy and ovate. Popular in Tamil
Nadu and occupies about 3% of the total cane area. High sugared with 16—18%
pol. It is high fibered, hence suitable for sugar complex with cogeneration of
power. Juice quality is good. Jaggery is hard and crystalline. The yield potential is
over 100 t ha -1 .
(6) Co 6304 (Co 419 x Co 605). Vigorous thick cane, erect, and nonlodging which combines yield and quality, midlate in maturity. In Tamil Nadu, it is a leading variety and replaced the wonder cane Co 419. Occupies an area of over 11%. In Tamil Nadu it performed well under garden soil and wet soil conditions. Its yield potential is over 150 t ha-1 with 16—18% sucrose.
(7) Co 6415 (Co 1288 x Co 740). Medium thick cane, early maturing. Self
detrashing. Suited to the North Karnataka conditions. Extensive field trials were
conducted at the Karnataka Institute of Applied Agricultural Research (KIAAR),
Bagalkot district. The yield potential is 120 t ha - 1 with a pol in juice of 20—22%.
Good ratooner. It is drought tolerant but susceptible to smut.
32
6 Varieties of sugarcane
(8) Co 6617 (Co 312 x Co 1111). Medium thick cane, greenish purple in colour, early maturing, and vigorous growing. The yield potential is above 80 t ha -1 with a sucrose content of 18-19% in the juice. It is a good ratooner and an important variety of Rajasthan. Resistant to red rot and smut but susceptible to drought.
(9) Co 6806 (Co 775 x Co 798). Early rich cane with high tillering capacity with a millable cane population of 1.5 lakhs ha - 1 . Bud size is medium, ovate in shape. Cane is of medium thickness, purple in colour with a waxy coating. It is preferred in Tamil Nadu and Pondicherry. It is reported that in experimental trials conducted in Nigeria (Africa), the variety has done well. It has resistance to smut and red rot. Self detrashing. It has high fibre without dispensing sucrose content. The yield potential is over 110 t ha -1 with a pol of 20-22% in the juice. It is a good ratooner. It is profuse flowering with a good combining ability.
(10) Co 7218 (Co 449 x Co 658). Medium thick with early maturity. The colour
ranges from yellowish to purplish with a moderate yield and sucrose. It is suitable
for growing in West Bengal.
(11) Co 7219 (Co 449 x Co 658). Midlate, medium thick cane and drought toler
ant. It has a 'stay green' character (Arabidopsis) hence valued as fodder. It was
released in Maharashtra as 'Sanjivini'. It has spread to some parts of Andhra Pradesh
and Tamil Nadu. It is a promising variety in North Karnataka and is considered as
a supplement for Co 740. It is a high yielder with good quality and a better ratooner.
It is moderately susceptible to smut and red rot. Its performance at Agricultural
Research Station (ARS), Sankeshwar is presented here (Table 6.1).
T a b l e 6.1 Performance of Co 7219 at ARS, Sankeshwar (3 years average 1980-83)
Parameters Co 740 Co 7219
Cane girth (cm) 2.81 2.82
Cane length (m) 1.88 2.20
Cane weight (kg) 0.95 1.20
Millable canes (x 103) ha"1 96 96
Pol in juice (%) 19.23 20.34
Cane yield (t ha"1) 96 104
CCS yield (t ha"1) 12.22 14.08
Source: R. S. Khot (Pers. Commn.).
33
Sugarcane in agriculture and industry
(12) Co 7314 (Co 1287self). It is early maturing, medium thick cane with yellow
ish or purplish green colour. It is high sugared (> 18% pol) and maintains the
quality for a long time. It has been released in Madhya Pradesh and Haryana.
Quality of jaggery is good.
(13) Co 7704 (Co 740 x Co 6806). Early rich cane and matures in 10-11 months.
Its performance was good in Southern Karnataka. Its yield potential is 120—
150 t ha -1 with a sucrose content of 20-22%. Tillers well with a high millable
cane population. It flowers profusely. It is resistant to drought, smut, and red rot,
and is a good ratooner.
(14) Co 7717 (Co 419 x Co 775). Medium thick to thick greenish cane with hard
rind. Bud is medium sized and ovate in shape. The variety surpasses Co 1148 in
yield and quality in subtropical India. Its yield potential is over 100 t ha - 1 with
18% sucrose in the juice. It is a good ratooner but flowers profusely. The variety is
moderately susceptible to red rot. Leaf sheath is spiny, hence manual harvesting is
difficult. However, clasping of leaf sheath is loose.
(15) Co 7804 (Co 740 x Co 6806). Thick cane and recently released in Karnataka.
It is a high yielder with a high sugar content. It tillers heavily with a good rat ion
ing ability. It has a fair degree of tolerance to red leaf spot. At the 6th month stage,
it has an LAI of 7.0 with an LAD of 465-485 days. Under experimental condi
tions it has a yield potential of 175-200 t ha - 1 , with 20.54% sucrose in the juice.
It is a good ratooner and flowers moderately.
(16) CoA 7601 (Co 678 x Co 775). Early rich, medium to thick cane, purplish
green in colour, rind is hard. Eye bud is plumpy, and ovate. Erect in habit. It is
early maturing with a high juice quality. Its yield potential is 100-110 t ha - 1 with
a sucrose content of over 20%. The purity of juice is 88% even in the 6th month
and maintains the quality up to 300 days. It is susceptible to drought, rust, and
smut. Jaggery is of good quality with light brown colour, hard, and crystalline. It
is grown mainly in Andhra Pradesh and its performance has been good in the
coastal areas. It is heavy flowering.
(17) CoA 7602 (Co 1287 x Co 775). Medium thick to thick cane with purplish
green colour turning purple on exposure. Lamina are broad but spines are not
profuse. It is recommended as a mid season ripener in Andhra Pradesh to replace
Co 975. Variety CoA 7602 is drought and red rot tolerant. It yields about 95 t ha -1
with over 20% sucrose in the juice. It is susceptible to smut and grassy shoot
diseases. The quality of jaggery is good.
34
6 Varieties of sugarcane
(18) CoC 671 (Q 63 x Co 775). It has revolutionised the sugar industry in Peninsular India. It lends credence to our observation that it performs well in medium to heavy black soils presumably due to the shallow root system.
It is an early rich cane and matures in 10 months but retains quality up to 1 3 -
14 months. CoC 671 is a thick cane with pink colour, spines are many, and the
lamina is broad. It is known for vigorous growth and is resistant to smut. But it is
susceptible to red rot. It has occupied a major area in the vertisols of Northern
Karnataka and Maharashtra. It is a moderate ratooner but responds to manage
ment practice. Its yield potential is over 125 t ha -1 with over 2 0 % pol in the juice.
Very high juice purities of 90% and above have been recorded. Surprisingly its
performance in alfisols of Southern Karnataka is poor.
(19) Co 8011 (Co 740 x Co 6304). Midlate thick cane with a good yield potential.
It is shy flowering. Its performance in North Karnataka and Maharashtra is satis
factory. Its appearance is good.
(20) Co 8014 (Co 798 x Co 775). It is a promising, midlate (12-13 months to
mature), medium thick, green cane. It is doing well in North Karnataka, the Krishna
and Godavari districts of Andhra Pradesh. The pol in juice varies between 2 1 -
22% with about 16% fibre.
Field trials have shown that the height of millable cane is 2.5-3.0 m, canopy
colour is dark green. The eye bud is small. There is no internodal split. Shy arrowing
or non-arrowing. There are no spines on leaf sheath or lamina, hence facilitates
manual harvesting. It is nonlodging. It is resistant to smut but susceptible to
grassy shoof disease.
The performance of plant crop of Co 8014 and two ratoons at ARS, Sankeshwar
is presented in Table 6.2.
T a b l e 6 . 2 Performance of Co 8014 at ARS, Sankeshwar (1987-1990)
Variety Cane yield CCS yield Pol % in Fibre %
(t ha -1) (t ha -1) juice in cane
Co 8014 113 14.83 18.63 16.30
Co 7219 98 13.45 18.77 16.84
Co 740 92 11.30 17.73
Source: R. S. Khot (Pers. Commn.).
35
Sugarcane in agriculture and industry
In a big mill test conducted at Godavari sugar mills, Co 8014 gave a sugar recov
ery of 12.68% as against 11.56% by Co 740. On balance, Co 8014 is considered
a replacement for Co 740 and Co 7219. The cultigen Co 8014 is suitable for
early and mid season crushing.
(21) Co 8021 (Co 740 x Co 6806). It is a midlate, thick purplish green cane, and
high yielding. It is erect, shy tillering, and can be accommodated under narrower
spacings. The pol in the juice varies from 18-20%. It is non-flowering, predomi
nantly grown in Tamil Nadu, Gujarat, and Karnataka. Since it has high fibre, it is
useful in a sugar complex with cogeneration of power.
(22) Co 8371 (Co 740 x Co 6806). Midlate, thick cane. It combines high yield
with good quality. It is promising. It has large internodes, low tillering. Millable
cane population is low, hence preferred under high density planting. It is hard to
detrash. Its growth is promising in parts of Maharashtra and Karnataka (Table 6.3).
It has recorded yields above 180 t ha -1 with 20.19% sucrose.
It is seen that in peninsular regions Co 62175, a high tonnage variety, can be
replaced by Co 8371. This cv is tolerant to waterlogging, drought, and smut.
All India Coordinated Research Project proposes to release this variety in the
peninsular region. Based on 24 plant crops and 11 ratoons the average yield is
118 t ha - 1 with a sucrose content of over 20%. A highest yield of 185 t ha - 1 has
been recorded. The CCS yield of the plant crop is 27 t ha -1 while that of ratoon
is 22 t ha - 1 . The fibre content ranges from 11.8 to 12.0%. It is good ratooner and
is resistant to both drought and waterlogging. It is susceptible to red rot.
(23) Co 85002 (Co 62198 x Co C 671). It is a early maturing variety. It performs well in Tamil Nadu and Karnataka. It is a pre-release variety and is suitable wherever CoC 671 has problems. Data collected over a period of five years from ARS, Sankeshwar clearly established the superiority of Co 85002 over CoC 671 (Table 6.4).
36
6 Varieties of sugarcane
It is observed that on an average Co 85002 produces 14 and 1.83 t ha - 1 of more cane and CCS yield respectively over CoC 671. One striking feature is that Co 85002 is a better ratooner than Co C 671.
(24) Co 85004 (Co 6304 x Co 740). It is early maturing, medium thick variety
identified at Jamkhandi Research Station. Good ratooner and was recommended
for release under the All India Coordinated Project for the peninsular zone. This
variety is suitable for early to midlate crushing.
(25) Co 86032 (Co 62198 x Co C 671). It is the most promising variety of the
peninsular zone comprising Karnataka, Kerala, Tamil Nadu, Maharashtra, Gu
jarat, Madhya Pradesh, and interior Andhra Pradesh. It is erect, good tillering,
and a midlate variety. It has attractive features with a dark green canopy. It has a
few hard deciduous leaf spines and sparse splits. The cane is solid without pith
formation. It is shy—flowering to non-flowering. Maintains the quality for 2—
3 months. It is good for jaggery making. It is an excellent ratooner and stands
multi-ratooning under good management. It is resistant to smut, and tolerant to
salinity, and moderately resistant to wilt.
37
Sugarcane in agriculture and industry
A total of 24 field trials spread over 13 locations were conducted and it proved
its superiority over the local checks. Relevant data are in Table 6.5.
A big mill test was conducted at Pravaranagar Sugar factory, Maharashtra and
has given 1.0 to 1.5 units more sugar recovery. It is already released in Maharash
tra for commercial cultivation. A big mill test (BMT) was conducted on Jan 1 8 -
19, 2000 at Godavari Sugar Mills, Sameerwada. The relevant data are here under
(Table 6.6).
It is seen that Co 86032 established its superiority over Co 8011; the later needsl to be phased out. For the BMT about 500 tons of cane of each Co was used.
(26) Co 87025 (Co 7704 x Co 62198). It is a midlate variety with a good yield and quality. Erect cane, easy to detrash and nonlodging. Good for high density planting. It is a good ratooner. It is conceived that this variety is amenable to mechanical harvesting. Yield and quality parameters of 2 plant crops and one ratoon are presented in Table 6.7 (Srinivasan and Bhagyalaxmi, 1995).
6 Varieties of sugarcane
Some salient features of this variety are: it is a medium thick cane, attractive
field appearance, with purple cane and a heavy wax coating. Buds are small but
the internodes are long. It is practically free from water shoots or lalas. It exhibits
tolerance to drought, smut, and red rot.
(27) Co 87044 (Co 62190 x CoC 671). A high yield, fast growing, midlate variety with a high sucrose content. Tends to lodge under loose soil conditions. Tolerates drought and is suitable for mid season crush.
(28) CoC 85061 (Co 6304 GC). Early maturing, medium thick green cane. Combines high yield with good sugar content. Good ratooner with drought resistance. Ideal for midseason crushing. The potential yield is 90-100 t ha-1.
(29) CoC 90063 (Co 6304 x CoC 671). Erect, nonlodging, early to midlate variety. It is high tillering with a good yield and quality. Slow initial growth but picks up later. Harvesting advised between the 11th and 12th month. Resistant to red rot. Good ratooner. The yield potential is 110-120 t ha -1 .
(30) CoC 92061 (Co 7314 GC). Thin cane, early ripener with a high yield and sucrose content. This variety needs monitoring as it is susceptible to red rot. Should be harvested in the 11th month, failing which pith formation takes place.
(31) Co] 64 (Co 975 x Co 617). Like Co C 671 in tropics, this variety has revolu
tionised sugar industry in subtropical India. Early rich cane, medium, straight
green colour with pellet like bud having a depression at the top between the bud
and the internode. Germinates well with a high tillering capacity. Canes are solid,
non-pithy, and nonlodging. It combines good yield with high sugar. The yield
potential is 100 t ha - 1 with 16—17% pol in juice. The fibre content is 14% and
susceptible to top shoot borer. Moderately resistant to red rot and excellent ratooner.
It is a leading variety in Punjab, Haryana, and Uttar Pradesh.
(32) Co] 81 (Co 798 x Co 775). It is a midlate to late, medium thick cane with
yellowish green to purple colour. It is high yielding and a good ratooner and was
found promising in Punjab. It is frost resistant.
(33) CoLk 8001 (Co 62174 x Co 1148). It is an early rich thick cane with a purple
or yellow tinge. It is a selection from IISR, Lucknow. Fast growing, vigorous, and
high yielding. It might supplement Co 1148 and Co S 767. It tolerates water
stress conditions and has a moderate resistance to red rot.
39
Sugarcane in agriculture and industry
(34) Co R 8001 (Co 740 x Co 1287). It is intended for Adsali planting in Telan-
gana region of Andhra Pradesh. Purplish/dark green colour, thick erect cane. Its
performance is better than Co 419. It is tolerant to drought, and resistant to red
rot.
(35) CoS 767 (Co 419 x Co 313). Midlate, medium thick green to purplish cane.
It is found to be better than Co 1148 and Co 1158. Resistant to drought and red
rot, but has a tendency to lodge.
(36) CoS 8118 (Co 1158 GC). Midlate, thin to medium thick green cane. Doing
well in most parts of Uttar Pradesh with a moderate yield and quality. Well suited
under abiotic stresses.
(37) CoS 8422 (MS 6897 x Co 1148). Midlate, thick yellowish green cane and
coming up well in Eastern Uttar Pradesh.
(38) BO 70 (BO 24 x BO 3). It is a midseason cane and is doing well in central parts of Uttar Pradesh. It is distinctly superior in yield and quality when compared to the standard variety Co 1158. The loss in the final stand is compensated by the cane weight. It is a good ratooner. It is tolerant to drought and waterlogged conditions, but moderately resistant to red rot. Jaggery of this variety is of excellent quality, as it is light brown in colour, granular, hard and retains quality. It has yielded 76.8 t ha -1, with a sucrose content of 17.2% and a juice purity of 85.8%.
(39) BO 72 (BO 29 x Co 658). Medium straight green cane, and the rind is not
hard. Bud is medium sized, plumpy, and ovate. It is mid early maturing and ready
for harvest by December. It is moderated in cane and sugar yield. It is moderately
resistant to the diseases occurring in Bihar. Grown in Bihar and parts of Uttar
Pradesh.
(40) BO 74 (BO 14 x BO 22). It is a main season cane in Bihar and a good
ratooner. Medium thick cane, erect, slightly oval in cross-section, and the rind is
hard with a greenish or purplish yellow colour. Buds are medium sized, plumpy
with a tendency towards oval shape. It was released for general cultivation in 1974
and occupies 3% area. The yield potential is 100 t ha - 1 with 10% recovery. The
variety is moderately susceptible to red rot.
(41) BO 76 (BO 32 selfed). Medium thin, straight, purplish green colour with a
hard rind. Bud is medium sized, plumpy, and oval shaped. The variety was re-
40
6 Varieties of sugarcane
leased in 1974 in Bihar and occupies 3% area. Blind nodes (nodes without buds) were observed in Pusa, Bihar. It yields 90 t ha-1 with a 10% sugar recovery in Bihar. It is resistant to red rot and tolerant to waterlogged conditions. Foliage remains green and serves as useful fodder.
(42) BO 91 (BO 55 x BO 43). Midlate and a leading variety in Bihar with good plant and ratoon yields. Cane is heavy, erect, and highly resistant to red rot and smut. Yields 72-76 t ha-1 with a sucrose content of 12-15%. It withstands abiotic stresses like floods, drought, alkaliniry, and salinity.
(43) BO 99 (Co 1207 x BO 43). Early cane, grows well in the sandy loam soils of Bihar. Good for jaggery and a good ratooner. It withstands waterlogging, salinity and alkalinity, and is resistant to red rot and smut.
(44) BO 102 (BO 47 GC). Early, medium thick cane, resistant to waterlogging, red rot, and smut. Suitable to the conditions in Bihar.
(45) BO 108 (Not available). Midlate, medium thick cane, found suitable for the sandy soils of Bihar for main season crushing. Resistant to smut and red rot.
(46) BO 109 (Co 1193 x BO 32). Early to midlate variety and suited to early and midseason crushing in Bihar. Withstands drought, waterlogging but cannot withstand salinity or alkalinity.
The sugarcane varieties under cultivation in different States are given in Table 6.8 (Srinivasan et al., 1995).
Table 6 .8 Sugarcane varieties under cultivation in different sugarcane growing
States
State Varieties
Andhra Pradesh Co 6907, Co 7219, Co 7805, Co 8011, CoR 8001, Co 62175, Co 6304, CoC 671, CoC, 85061, Co 8021, CoT 8201, Co 7704, Co 8013
Assam Co 1008, Co 8315, Cojr 1, Cojr 2, Co 1132
Bihar Co 1148, Co 1158, CoS 767, BO 91, BO 99, BO 102, BO 108, BO 109, BO 110, BO 120
Gujarat Co 8338, Co 6304, Co 6806, CoC 671, Co 7527
contd.
41
42
S Varieties of sugarcane
6.1
AN ERA OF THE EARLY AND SHORT DURATION VARIETY
Efforts were made in the early 1930s to develop early maturing canes by crossing sugarcane with maize and sorghum but it was not successful. However, biotechnology offers immense opportunity to develop early rich canes. The prime objective is to fit cane into multiple cropping systems and enhance the intensity of cropping. In short, 3 crops (one plant and two ratoons) can be taken in 24 months. Early rich canes are those cultivars which mature in 10 months with 20% pol and the production potential is 8—10 t ha -1 mo - 1 sugarcane or 1 t ha -1 mo - 1 sugar. A milestone was reached when early rich canes like CoC 671 CoJ 64, Co 7704, CoA 7601, and KH 3296 (sparse flowering) were released for commercial cultivation. This author asserts that CoC 671 can perform well even in 'difficult to ripen' areas such as coastal Karnataka. These early canes mature in 10 months and retain the quality for 1-3 months. The release of Short Duration (SD) varieties is relatively recent. As excepted, SD varieties are low yielders, but are fast and vigorous growing, since the growth period is short. The SD varieties should fulfil the following conditions:
(a) matures in 8 months with 16% pol and 8 5 % purity
(b) the production potential is at least 8 5 % of the leading variety
(c) it maintains the quality for 2—3 months.
Six SD varieties were identified in 1983- They are Co 8336, Co 8337, Co 8338, Co 8339, Co 8340, and Co 8341. The most promising SD varieties are Co 8338 and Co 8341. A brief description of Co 8338 and Co 8341 follows:
Co 8338 (Co 7413 x Co 6806) is a purple coloured, medium thick cane of high quality with moderate yields. Records 17-20% pol even in the 8th month. This variety was released in Gujarat to replace C o C 671 in wilt affected areas as it is resistant to wilt and smut. It is a good ratooner.
Co 8341 (Co 7507 x CP 34-79) is a medium thick cane of high quality. It has registered 18.58, 89-9, and 11.96 per cent sucrose, purity, and fibre respectively after 240 days. It is resistant to smut.
These early and SD varieties respond to azotobacter, i.e. free living N2 fixers.
43
do mo
- .1
Flowering: a bane in commercial plantation
An old belief in ancient India was that the flowering of sugarcane in a kitchen
garden heralds the death of a person in that home. This was more a superstition.
Sure enough, flowering ushers the death of the cane. A sugarcane flower is an
inflorescence with thousands of flowers on the main stalk. As 'ripenesss to flower
stage' approaches the internode elongates and the leaf blades shorten. A small leaf
(SLF) is formed indicating that the inflorescence is formed. The last leaf is long
enough to enclose the panicle or inflorescence. The flower in sugarcane is called
arrow/tassel or panicle and takes about 2 weeks for formation in different varie
ties. The short blade, or SLF, or flag leaf is known as the boenting stage. The SLF
is reported to contain higher reducing sugars and has lower sucrose content when
compared to the normal leaf. The flowering in cane is limited to 7—8 days and the
entire flowering is normally over in 6-8 weeks. The flowering terminates growth
and is mostly hereditary. There are shy, non-flowering and profusely flowering,
varieties. In general, the Officinarums flower more profusely than the other related
species. The varieties which have more Officinarum components tend to flower
more. In the Northern hemisphere flowering occurs during October—November,
and in the Southern hemisphere it occurs during May-June. The flowering is
highest in the tropical latitudes, particularly, 5 to 15° N and S. In the subtropics
flowering is less pronounced or absent due to the low temperature.
Among the different varieties, Co 421 flowered profusely in Kenya, Burundi,
Rwanda, Mozambique, Nigeria, and Zimbabwe in the African continent. However,
this variety did not flower in Tanzania (4° S latitude) at an altitude of 700 m. Inter
estingly, B 37172 is reluctant to flower anywhere in the world. Some varieties like
Co 421, Co 62175 show pithiness or 'piping' after flowering. But N C o 310 showed
no 'piping' but maintained quality up to 6 months after flowering. Similarly CoC
671, an early rich cane grown in tropical India maintained quality up to 3—4 months
after flowering. But in Trinidad and Tobago in the Caribbean which is at a low
altitude flowered cane deteriorated rapidly. In the tropical parts of India (8-18° N
latitude) KHS 2045 is a non-flowering cane, while KHS 396 is shy flowering.
Among the external factors, photoperiod is important. Sugarcane is a short-
day plant and flowering occurs when the day length gets reduced with the increase
in nyctiperiod (night length). According to Clements (1980) flowering induction
generally occurred when the nyctiperiods ranged from 11 h 35 min. to 11 h 40 min.
Some biotic and abiotic stresses influence flowering. A high soil moisture status
47
Sugarcane in agriculture and industry
and fertility induce flowering. At the equator, where both day and night lengths,
are equal, flowering can take place round the year. The temperature is another
important factor. The minimum temperature for flowering is 15—18 °C, but the
optimum temperature is 21—27 °C. An interaction between elevation and tem
perature has to be reckoned with. At higher elevations, the lower temperature
reduces or inhibits flowering. The age of the plant is equally important. Thus
sugarcane should-pass the juvenile stage, and should have at least three joints to
produce enough 'flowering stimulus', or florigens to induce flowering. In Nigeria,
sugarcane flowers in April-May, but when reaped in February-March, the flower
ing in ratoons is suppressed as it has not passed the juvenile stage. Similarly in
Mandya (12° N latitude), the cane planted in June will not flower that year and can be
reaped in the following year, during February—March (18—20 months).
The physiology of sugarcane is well detailed by Coleman (1968). The first step
involves the exposure of the plant to a high light intensity (> 12 h) during 'ripeness
to flower stage', followed by a critical dark period of 11.5 h. During the dark
period, flowering stimulus is formed which is translocated to the sink (apex). The
accumulation and fixation of 'flowering stimulus' or florigen takes place at the
apex. This is followed by the differentiation of floral primordia. Julien (1968) has
given an interesting account of the flowering process in sugarcane. The spindle
and the first leaf are most sensitive to floral induction and produce more 'flower
ing stimulus' (Fig. 7.1). By this reasoning, he states that the presence of leaf one is
vital for optimum flowering. On the other hand, older lower leaves may possibly
produce a transmissible inhibitor which prevents the growth of inflorescence pri-
mordium. It is assumed that the flowering stimulus is translocated from the spin
dle leaf No. 1, the spindle and even from the roots to the apex, where it gets fixed.
For flowering stimulus, possibly some enzymes are translocated with the assimi
late stream in the phloem. The conditions for sugarcane flowering include a ma
ture plant, 12 h photoperiod, temperatures above 18 °C, low soil N, and abun
dant water at the time of initiation.
The physiology of flowering, albeit obscure, suggests that the removal of the
source, i.e. leaves, especially the spindle 1, 2, leaf, etc. would suppress or inhibit
flowering in sugarcane. For commercial plantation, flowering results in a great
setback. It arrests the growth, favours side shooting, pith formation, sets a ceiling
on the yield, and quality with a decreased extraction per cent and juice purity.
Hence flowering control was attempted by spraying chemicals such as maleic hy-
48
Sugarcane in agriculture and industry
The earliest attempt was the withdrawal of water during the 'ripeness to flower
stage which was difficult to achieve in a monsoon type of climate. It has been
observed that a spray of paraquat or Gramaxone at the rate of 3—5 1 ha - 1 dissolved
in 900 1 of water (high volume spray) during 'ripeness to flower stage' would
completely suppress flowering in the profusely flowering varieties such as Co 419
and Co 62175.
A partial or complete inhibition of flowering would increase the yield and
quality as shown: (Hunsigi et al., 1975)
A sample of 50 clumps were taken with manual defoliation of the leaves and
spindle at the boenting stage, i.e. in the first fortnight of August at Mandya (12°
N latitude) (Cv. Co 62175).
The suppression of flowering is effectively achieved in ratoons by spraying
ethrel (Ethepon) at 500 ppm during the 'ripeness to flower stage'.
In certain varieties, which do not deteriorate fast even after flowering, this can
be an advantage. Such flowered cultivars give an improved yield and quality. But
more often than not, flowered canes deteriorate fast and cannot be used for seed
purpose even as a contingency plan. In Hawaii, a 2-year crop can suffer an yield
loss to the extent of 20% due to flowering.
Thus, a profusely flowered cane reduces the yield to the extent of 2 5 % and
sucrose upto 1%. Flower suppression/inhibition seems to be an important step in
sugarcane production technology. However the methods employed are drastic,
such as desiccation and dehydration, and it is hoped that future agronomists will
have better recourse to control flowering in sugarcane.
50
Sugarcane soils
Soil resource must be recognised as a dynamic living system that emerges through
a unique balance and interaction of its biological, chemical, and physical compo
nents. It has an inbuilt ability to heal itself provided man's intervention has not
made drastic changes. The term soil resilience implies its ability to bounce or
spring back into shape or position after being stressed. Soil resilience depends on
the balance between restorative or degradative processes. Soil quality is its capac
ity to function. The selected indicators of soil quality are organic matter status,
infiltration, aggregation, pH, microbial biomass, bulk density, soil depth, con
ductivity/salinity, and nutrient status.
Sugarcane is not specific to soil requirement. It is a glycophyte confined to the
tropical and subtropical irrigated regions of the world. Being a giant grass, it can
be grown on any type of soil. The soils range in depth from shallow to medium to
deep soils. The soils of the sugarcane belt are detailed by Beater (1957). In India,
it is grown on soils such as red, medium to deep black, laterites, and alluvial soils.
Productivity is high in red, medium, black, and alluvial soils (Table 8.1) which
have good internal drainage (Hunsigi, 1993). The National Commission on Ag
riculture observed that the highest production potential is in peninsular India.
Soil types per se have no significant influence on the yield and quality of cane
provided they are not problematic, namely, saline, sodic, and acid soils. In Barba
dos sugarcane is grown in alkaline 'Rendzina' and 'terra' soils derived from coral
limestone (Blackburn, 1984). In Guyana it is grown in acid sulphate soils (Pegasse
soils) or cat clays with a pH less than 2.0. Here Al toxicity is encountered and the
roots become stubby or corolloid. These cat clays are reclaimed by irrigating with
sea water (Blackburn, 1984). In West Africa cane is grown on seasonally flooded
wetlands along the river banks called Tadamas'. But the yield decline in most parts
of Africa is attributed to the soil loss through erosion. In the Fujian oxisol, sugar
cane is grown in the 'talasigd grasslands dominated by the Pennisetum sp. They
are literally sunburnt lands. In Brazil cane is grown in alfisols {Terra Roxa misturadd).
Based on physiographic and climatic variations, the soils of India have been
divided in to four broad soil groups (Sehgal, 1991).
1. Forest and Hill soils of the Himalayan mountains
2. Alluvium derived soils of the Great plains
3. Black cotton soils of the peninsular region
4. Red and lateritic soils of the peninsular region
51
Sugarcane in agriculture and industry
Table 8.1 Major sugarcane growing soils of India
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
State
Andhra Pradesh
Assam
Bihar
Gujarat
Haryana
Karnataka
Madhya Pradesh
Maharashtra
Orissa
Punjab
Rajasthan
Tamil Nadu
Uttar Pradesh
West Bengal
All India
Major soils
Black, alluvial
laterites
Alluvial,
Tilla lands
Alluvial
Medium and deep
black, alluvial
Alluvial
Medium and deep
black, red soils
Medium to heavy
black
Medium to heavy
black
Red, black,
laterite
Alluvial
Deep and medium
black
Black and alluvial
Alluvial
Alluvial
—
Sugarcane productivity (t ha"1)
71.5
42.4
37.2
71.9
53-2
87.1
37.7
76.0
58.5
56.2
50.4
110.5
59.4
71.5
66.5
Source: Hunsigi, 1993.
52
8 Sugarcane soils
The last three soils mentioned are important from the point of view of sugar
cane cultivation. The alluvial soils are grouped in order—entisols, inceptisols,
and aridisols. They are generally deep, well to imperfectly drained, sandy loam to
clay loam in texture. The soils test low in nitrogen, low to medium in phospho
rus, and medium to high in potassium. Recent surveys suggest that they have
multinutrient deficiencies of sulphur, zinc, and iron. The recent alluviums are
locally termed as Khadar and old alluvia as Bhangar. The Indo-Gangetic alluvi
ums of North India are fine textured and are important sugarcane soils. They are
deep with good internal drainage. In Central Uttar Pradesh, the soils are sandy
loam and slightly alkaline in reaction. In Eastern Uttar Pradesh, two soil types are
met, namely, bhat and hangar avA the third one is developed from inundation from
rivers called Doab. Sugarcane is grown without irrigation in Doab soils. Bangar soils
are light textured, loam to sandy loam with shallow water table and a lower lime
content. The soils of Bihar are calcareous with a high lime content ranging from 0.5
to 20% (Calciorthids). The texture is sandy loam to clay loam with alkaline reac
tion. These soils are rich in potash and poor in phosphate. Phosphate fixation is also
high due to the presence of CaCO3 The alluvial soils of Punjab have poor structure
with hard pan or Kankar. The soil problems in Punjab are poor structure and drain
age. The sugarcane soils in West Bengal and Assam are mainly alluviums developed
in riverine lowlands. They are subject to erosion. In Assam, the Tilla lands are acidic
in nature.
The black cotton soils of peninsular India (vertisols) are derived from the Deccan
Trap with variable soil depth. They are extensive in Maharashtra, Gujarat, Madhya
Pradesh, Andhra Pradesh, Karnataka, and Tamil Nadu. These are locally called
Regur in Central India and Bhal in Gujarat. The vertisols have high 'swell-shrink'
potential. They are highly sticky and plastic when wet. The exchange capacity is high
(35-55 meq/100 g) with a high base saturation. The pH is mostly alkaline. Because
of their cracking nature, they are called 'self-ploughing' soils. In compacted soils
cane makes its way through a network of biopores and cracks to extract water and
nutrients. Conservation tillage and minimum tillage is advocated to favour for
mation of biopores, a practice known as biological 'drilling'. These soils are mostly
productive due to their inherent fertility and high moisture storage capacity. Nev
ertheless, they should be managed well lest they develop salinization, low infiltra
tion rate, and low workability under moist and dry conditions.
53
Sugarcane in agriculture and industry
Red soils occur in Andhra Pradesh, Karnataka, Tamil Nadu, Goa, parts of Bi
har, Assam, and Uttar Pradesh. They are found in association with true laterites.
These soils are generally loam to clay loam in texture but may also include sandy
loam to heavy clay loam. The soil depth ranges from shallow to very deep. The
pH is slightly acidic to neutral. The sequioxide ratio is high. The CEC and base
saturation is low and the CEC ranges from 15-25 meq/100 g. The soils are se
verely deficient in organic matter, nitrogen, phosphorus, and lime but well sup
plied with potassium.
The relationship of soil biota consisting of microflora and microfauna are of
vital importance in plant growth and development. Table 8.2 indicates that the
population of soil biota is more in alluvial soils followed by medium black soils.
Further, soil acidity (pH 4.5—5-5) is favourable to the development of the fungi.
Soil bacteria prefer neutral conditions (pH 6.5-7-5). Actinomycetes thrive well in
slightly alkaline condition. In sum the yield and quality of cane depend on the
soil type and its biofertility.
Table 8.2 Distribution of microorganisms in different soils
1.
2.
3.
4,
5.
Soil
Deep black soil
Medium black soil
Alluvial soil
(Goradu soil)
Lateritic soil
Red soil
No. per gram of soil in the upper 15 cm layer
Bacteria
1,288,000
14,940,000
20,110,000
1,060,000
1,336,580
Actinomycetes
104,100
286,100
264,000
470,100
622,150
Fungi
33,310
9,745
33,850
118,000
8,294
Source: Sehgal, 1991.
The ideal soils for sugarcane are deep (60 cm), well drained, well structured,
clay loam to sandy loam with lots of organic matter.
The physico-chemical characteristics of soils which influence yield and quality
of cane are: pH, CEC, texture, and structure, compaction or bulk density, organic
matter content, and water retention capacity. It grows and yields well at a pH
range of 5-5 to 7.5. But the lower limit is 4.5 and the upper limit is 8.5. The ideal
pH range is 6.5 to 7.5.
8 Sugarcane soils
The CEC of soils decides the release and retention of plant nutrients, and
sugarcane soils should have a minimum CEC of 15 meq l 0 0 - 1 g soil. T h e CEC is
also influenced by organic matter content, which is an index of sustainability.
Among the textural class, very sandy porous soils are low yielding with a re
duced ratooning ability. If the surface soil is sandy, it is also infested by nema
todes. In fine textured soils, porosity could be low with water occupying the air
spaces resulting in reduced aeration. Sugarcane roots require 10 to 12% aeration
for respiration (Humbert, 1968). Soil 'capping' can also occur in silty or fine silty
soils with reduced germination, plant stand, and yield. Ideally total porosity should
be 50% with the pore size distribution as: large pores (d 10 μ), medium pores
(d = 10—0.2 μ) and fine pores (d < 0.2 μ) in the ratio of 1 : 1 : 1.
The arrangement or aggregation of soil particles is known as structure and the
ideal structures are the crumb or granular structures. It decides the soil-plant-water
relationship. To maintain crumb structure, application of organic matter, green
manuring, crop rotation and intercropping with soil restorative crops (legumes) is
essential. Only the aggregates of 0.25 mm are responsible for the stable soil structure.
Continuous cropping with sugarcane spoils the soil structure (Zende, 1981).
Soil compaction is a major disorder in sugarcane fields and attended with
many problems such as lack of aeration and restricted availability of water and
nutrients. Compaction takes place due to trafficking and ratooning. The Bulk
Density (BD) of sugarcane soils ranges from 1.05 kg m-3 (organic soils) to
1.52 kg m - 3 in heavy clays. The BD values increase with depth. In entisols of
IISR Lucknow, BD values were 1.48, 1.50, 1.54, and 1.60 g c m - 3 in 0-15,
15-30, 30—45, and 45-60 cm soil depths respectively. The suitable BD for cane
is 1.2 to 1.3 kg m - 3 . As the soil is compacted, BD increases with the reduced
mass and volume of roots. Root proliferation and extension is restricted in dense
soils. With a 5% pore space, there is little root development. Varietal differences
also exist to respond to soil BD. Cultivar Co 997 has more root CEC, and more
functional roots to resist higher BD values. The effect of compaction on per cent
root distribution is given in Table 8.3.
Monocropping, intensive cultivation, and excess irrigation result in soil com
paction leading to poor drainage and salt accumulation. Ultimately a hard pan is
developed at the root zone which creates a waterlogged condition. The imperme
able crust reduces the infiltration capacity. The available soil water is reduced.
The dense soils result in reduced uptake of nutrients such as P, K, and other
micronutrients. The net effect is high bulk density, poor infiltration rate, poor
55
Sugarcane in agriculture and industry
drainage, deterioration of soil fertility, poor nutrient uptake, and a consequent reduction in yield and quality. This condition is found in many sugarcane soils and is more pronounced in saline-alkaline conditions.
T a b l e 8 . 3 Effect of compact ion on per cent d is t r ibut ion of roots
(vertisols, cv Co 740)
Treatment
Normal
FYM added
BD values % Root distribution in different soil depths
(kg m-3)
1.2
1.4
1.6
1.2
1.4
1.6
3CM5 cm
12.4
10.6
9.4
19.1
14.3
14.1
45-60 cm
7.1
4.4
3.8
3.1
3.0
2.3
Source: Zende, 1981. Data partially modified.
Further evidence comes from the work of Torres and Villegas (1995) who ob
served a minimum yield loss of 10% due to compaction. The bulk density in
creased from 1.2 kg m-3 to 1.4 kg m-3 due to trafficking. When stools were dam
aged the yield reduction ranged from 21—45%. However, most compaction was
restricted to the 25-30 cm layer of the surface soil and very little at 50 cm depth.
Soil Organic Matter (SOM) is the key to sustainable crop production. SOM
improves soil properties such as infiltration and permeability. It also determines
the release and retention of nutrients. It is difficult to quantify the SOM level. But
ideally sugarcane soils should contain 2 to 5% SOM. Incorporation of trash and
subsequent decomposition and press mud application enhances the SOM levels
of cane soils.
Water retention and release is influenced by the soil type. The ideal water ca
pacity is 15 cm m-1 depth to provide adequate moisture to cane before the com
mencement of irrigation. As cane progresses in age, the soil water potential should
be 20 to 250 Kpa (0.2-2.5 bars). The water table should be kept at a depth of
0.8 to 1.0 m.
To optimise the cane yield, a nomogram has been developed for land use plan
ning by South African workers (Platford and Meyer, 1995). They observed that
56
8 Sugarcane soils
soil losses are severe at the 12% slope in erodable soils. The nomogram monitors to keep soil annual loss to less than 20 t ha-1 annum -1.
The long term studies (20 year period) by Gawander and Morrison (1999) indicate that a major factor for yield decline was the loss in SOM. A similar loss in SOM following cane cultivation was observed in Australia. They observed a decrease in soil pH from 5.5 to 4.5. The decline in CEC was to an extent of 20% and is attributable to the loss in SOM. But the bulk density increased from about 0.9 to 1.2 kg m - 3 in oxisols. Thus compactness was evident following cane cultivation. The retention of P declined linearly. The decline in Ca + Mg was much sharper (loc. cit.). However, the water retention at wilting point, i.e. 1.5 kpa [15 bars] showed a gradual increase with time. They conclude that the decline in SOM, associated decrease in CEC, and increased bulk density are the chief contributing factors detrimental to cane growth and yield. These factors are also responsible for increased soil degradation in the sugarcane belt. The result is the declining cane yields over a long period of time.
8.1
PROBLEM SOILS
The saline and sodic soils are widespread in the sugarbelts of the world. Sugar
cane is moderately susceptible to soil salinity. Varietal differences are noticed.
Varieties B 37172 and B 42231 are fairly tolerant to salinity. Similarly Co 86032
and Co 8371 tolerate some degree of saline conditions. The salinity threshold is
reported to be 1.7 d s m - 1 , and the yield decrease per unit increase in salinity
beyond threshold is 5-9%. A serious yield reduction occurs at a conductivity of
4—8 d s m - 1 . But very little growth and death occurs at 10 d s m - 1 . The symptoms
of cane grown in saline conditions are stunted growth, poor tillering, and leaves
turning yellow. They may have scorched tips and margins. Saline soils can be
reclaimed by irrigation and providing good drainage.
In sodic soils, Na destroys soil structure with poor cane growth. Quality is
impaired with reduced juice purities. Chlorides and bicarbonates can do irrepara
ble damage to sugarcane. The Exchangeable Sodium Percentage (ESP) is often
misleading due to the presence of ionic elements like Ca and Mg. Hence the
Sodium Adsorption Ratio (SAR) has been suggested to indicate sodicity of soils
and irrigation water. More than 50% yield reduction is noticed when the SAR is
57
Sugarcane in agriculture and industry
about 20. Blackburn (1984) has intuitively summarised the effect of sodicity on
sugarcane (Table 8.4).
Table 8.4 Effect of sodicity on cane growth
Parameters
SAR
pH
Cane healthy
13
8.2
Cane slightly affected
18
8.3
Cane severely affected
35
9.1
Cane dead
41
9.2
Source: Blackburn, 1984.
SAR = Na/(Ca + Mg)1'2
Sodic soils can be reclaimed by application of 1-3 t ha -1 of gypsum coupled with
irrigation. It may take 2 to 3 years or more to replace Na with Ca in the exchange
complex.
Attempts were made to delineate sugarcane soils of Karnataka by site specific,
soil specific soil survey and categorise their suitability as highly, moderately, and
marginally suitable based on the FAO model. The seven factors which govern the
yield are: texture, drainage, CEC, pH, soil salinity or sodicity, slope or relief, and
depth of water table. The relevant data are in Table 8.5 (Naidu, 1999). In the
present study the limitation ranged from 4—7 in the major sugarcane growing
regions of Karnataka. The climatic parameters such as rainfall, maximum and
minimum temperatures, and irradiance have also been taken into account while
delineating the sugarcane soils. The productivity, namely, kg cane per kg input
has also been worked out and is presented in Table 8.5 along with the number of
limitations and suitability class. It is worth noting that most of these soils are
responsive to proper management, which can help overcome the limitations and
produce a highly economic yield. But sugar recovery is more a function of cli
matic parameters which can hardly be changed, except aridity which can be miti
gated by a proper irrigation schedule. Similarly soil texture can hardly be changed
by agronomic manipulation which impairs the drainage system with a conse
quent reduced cane yield and quality.
In conclusion it is reasonable to postulate that management protocols hold the
key to cane production, and many soil limitations can be restricted or eliminated
which result in a higher cane yield and sugar output.
58
Ecology of sugarcane
Sugarcane is tropical by origin and all cultivation is in warm countries (Simmonds, 1986). But it is adapted to a range of tropical and subtropical climates and is grown from 37° N in Southern Spain to 31° S in the Republic of South Africa. It cannot tolerate freezing temperatures and growth essentially ceases at mean minimum temperature below about 12 °C. Nevertheless, sugarcane is grown under a wide range of temperatures, solar radiation and rainfall. Ideally sugarcane needs a long warm growing season and a fairly dry, sunny, cool but frost free climate at ripening and harvest, free from hurricanes and typhoons (Humbert, 1968). It needs reiteration that sugarcane requires two distinct climatic conditions, (a) A long, warm growing season with adequate rainfall/irrigation, long hours
of bright sunshine, higher relative humidities for rapid growth and dry matter build up,
(b) A ripening season of 2-3 months duration having warm days, clear skies and cooler nights and relatively dry weather without rainfall for build up of
sugar. Paradoxically, the coastal areas of Andhra Pradesh, Karnataka and Tamil Nadu
have higher temperatures and relative humidities for dry matter accumulation and higher yield. But these areas do not have distinct cooler nights, and hence are not conducive for sugar accumulation; this leads to low sugar recoveries.
These are 'difficult-to-ripen' areas. The climatic factors which influence yield and quality are temperature, rainfall, humidity, sunshine, frost, CO2 concentration, and wind. The effects of climatic factors on sugarcane are presented in Table 9.1. But key climatic elements affecting productivity of fertilized, well managed irrigated sugarcane on well drained soils are temperature and radiation. Further evidence comes from Evensen and his co-workers (1997) who state that under irrigated culture with high nutrient availability the pattern of yield accumulation is determined primarily by temperature and incident radiation, and this may perhaps vary with the cultivar. Thus yield is positively related to both temperature and solar radiation within the optimal region. This led Clements (1980) to conclude that 'the size of theoretical crop is determined by the energy available to it and its inherent ability to fit into the particular energy level'.
60
ft;a«a«?aa!^saisii»w^
9 Ecology of sugarcane
9.1
TEMPERATURE
The optimum temperature for growth is between 24—32 °C. Temperature less than 5 °C is harmful even for resistant varieties. Ambient temperature above 38 °C reduces photosynthesis with increased respiration. Plants look wilted even at 35 °C. Hunsigi (1993a) has shown that Modified Growing Degree Days (MGDD) range from 2000 to 6000 in sugarcane growing regions of the world. M G D D gives the 'effective degree' index and minimum daily temperature below 10 °C is equal to 10 °C and any daily maximum temperature above 32 °C is equal to 32 °C.
It was found that the emergence of shoots requires 1 50 degree days. Leaf area development is strongly influenced by temperature and M G D D s are between 150—200 degree days. Inman-Bamber (1994) maintained that peak stalk density occurred approximately 500 °C days after ratooning. Final leaf area increased linearly upto about 400 and 420 cm2 for leaf No. 16 of N C O 376 and N12 respectively. The phyllochron interval (leaf appearance interval) was 109 and 118 °C days upto leaf 14 and was 169 and 200 °C days thereafter for N C O 376 and N12 respectively. According to Inman-Bamber (op. cit.) the base temperatures for leaf and tiller appearance were 12 oC and 16 °C respectively. Keating et al. (1999) have developed models which simulate growth, water use, N accumulation, sugar dry weight and fresh cane yield for plant and ratoon crops in response to climate, soil management, and genotypic factors.
By far the most important climatic parameters are temperature and radiation. Low temperature reduces tillering—below 10 °C is definitely injurious. With increasing temperature, tillering increases until a maximum is reachad at about 30 °C. Temperature has a major role in carbon metabolism. Blackburn (1984) has shown that the minimum temperature for growth is approximately 20 °C but varietal and cultural factors modify this slightly. According to him, the critical temperatures for irrigated cane is 18-19 °C and for unirrigated cane 19—20 °C. The difference with irrigation is probably due to the alteration in temperature. Often the root temperature or soil temperature also significantly modifies the cane growth and development. The influence of critical temperature in two locations of Ethiopia is given in Table 9.2.
65
Sugarcane in agriculture and industry
Table 9.2 Effect of minimum temperature on yield and quality of cane
Parameters
Altitude
Mean annual temperature °C
Mean sunshine hours per day
Mean stalk NO ha _1
(ratoons of Co 419 and B4 1227) Mean cane yield t ha"1 year-1
Pol % cane
Source: Blackburn, 1984.
Location I
950 m
24.8
8.4
77,000
118
14.3
Location II
1,500 m
20.5 8.2
1,08,000
123
15.1
The interaction between temperature and elevation needs to be reckoned and as elevation increases ambient temperature gets reduced. Sugarcane is grown from sea level to an altitude of 1500 m.
9.2
RAINFALL
Sugarcane is grown in a wide range of rainfall conditions. It is grown where rainfall varies from 600—3000 mm. In areas with scanty and poorly distributed rainfall, irrigated crop is raised. Experience the world over suggests that sugarcane can be grown successfully with a uniform rainfall distribution of 1200 mm. The crop is more responsive to soil moisture than any other crop, since the vegetative portion is harvested. Under reasonable soil and management conditions, the response is 1 ton ha"1 per 100 mm of ET. Rainfall pattern dictates planting and harvest schedules. Monsoon climate is better utilised during grand growth phase and stalk elongation. But rainfall hinders ripening phase with consequent low sugar recoveries. Besides harvest and transport operations are hampered.
9.3
RELATIVE HUMIDITY (RH)
High humidities (85 to 90%) are conducive for growth and development. But 45-65% RH is desired for sugar build up in cane stalks. In coastal areas high
66
9 Ecology of sugarcane
humidities and high temperature favour good growth and high yields. But sugar recoveries are low.
9.4
ATMOSPHERIC C02 CONCENTRATION
Sugarcane benefits from increased atmospheric CO2 concentration. Generally photosyndietic rate increases as CO2 concentration increases from 0.01 to 0.07% but becomes saturated at 0.06%. Varietal differences have also been observed. A strong and positive interaction is found between CO2 and light. With increased sunlight, CO2 fixation is also increased.
9.5
SUNLIGHT
As indicated earlier, sunlight is another key element which influences the yield
and quality of cane. Sugarcane loves warmth and sunshine. Greater incidental
radiation favours higher sugar and cane yields. Cloudy days during sugar forma
tion lowers sugar yield with concomitant increase in starch production. The latter
hinders crystallization in the sugar mill. About 8-10 hr of bright sunshine are
conducive for yield and sugar output. Shorter days favour tasselling or flowering.
Sugarcane is grown in regions where irradiance is between 7 MJ m - 2 and 33 MJ m - 2
(1 MJ m-2 = 23.3643 cal cm -2). The open pan evaporation in these regions varies
from 4.5 to 9.0 mm d-1. However, best yields are obtained where solar radiation
varies from 12.84 to 25.68 MJ m -2 . Muchow et al. (1997) opine that at die average
incident solar radiation of 18.4 MJ m - 2 , the expected stalk yield is 420 t ha - 1 . They
also observed that biomass and fresh stalk yield would decrease from 18 months
to 24 months. As sugarcane is planted in wider rows, biomass accumulation during
early growth is expected to be lower than during later growth due to the long period
required for canopy closure. This supports the contention that early vigour is not
necessarily reflected in final yield. They also observed that the efficiency of radiation
utilization was much less for growth after 12 months than in the first 12 months in
a 2-year crop cycle. Maximum solar interception occurred from 120-200 DAP
(Days After Planting) and ranged from 61 to 73 per cent. After 12 months loss of
67
Sugarcane in agriculture and industry
biomass due to stalk death was important factor contributing to yield reduction. By
all standards, the optimum harvest period for cane grown in tropical regions is 12 -
18 months. Further, the physiological studies show that under good or bright sun
shine, stems are thicker, shorter and leaves are broader and greener. Under less sun
shine as is the case of cane grown as lower storey in coconut gardens, stems are
slender, and taller having thinner and narrower leaves.
Fig. 9 .1 Relationship between stalk plus biomass and cumulative intercepted
short-wave solar radiation (SR) and fitted linear relationship for the Makiki 1933-
1935 experiment (Muchowet al., 1997)
There is strong evidence to show that above ground biomass accumulation is
linearly related to cumulative intercepted solar radiation (Fig. 9.1). Radiation Use
Efficiency (RUE) has been studied and maximum RUE for sugarcane ranges from
1.7 to 2.0 g MJ - 1 . RUE for most C4 crops is 1.7 g MJ - 1 and for maize it is
1.6 g MJ - 1 . Thus sugarcane appears more energy efficient than most cereals with
68
9 Ecology of sugarcane
RUE values approaching 2.0 g MJ_1. Further, RUE of plant crops is 10% higher
and early canopy expansion is faster than in ratoon crops. In general tiller senes
cence occurred after the canopy closed beyond 7 0 % in te rcep t ion of
Photosynthetically Active Radiation (PAR) (Inman-Bamber, 1994).
9.6
FROST
In the North Indian belt, parts of Pakistan, Iran, Egypt, etc., sugarcane experiences frost, which seriously reduces yield and quality. A temperature of—1 to —2 °C kills the plants. Severe cold conditions adversely affect ratoon sprouting and tiller formation. Irrigation just prior to frost, and trash/polythene mulching mitigate frost to a great extent.
9.7
WIND
Velocity of 9-10 km h-1 will not harm cane, but if it exceeds 60 km h-1 cane lodges
and breakages occur. Due to high evaporation rate, ET is also enhanced with a
consequent reduced yield and quality.
Hurricanes and typhoons occur in the Caribbean, the Indian Ocean, and China
sea. Extensive damage is seen in Indonesia, the Philippines, Mauritius, etc. Stems
are blown over, become lodged, often broken and roots are formed at the nodes.
9 .8
MICROCLIMATE
Sugarcane as a tall plant has a distinct microclimate, where climatic factors like
temperature and humidity inside the crop canopy differ from conditions outside.
Variation in microclimate occurs due to increased humidity and decreased air
circulation. The humidity inside the crop canopy could be as high as 90-95%.
Parthasarathy (1972) notes that temperature inside crop canopy is 5—6 °C lower
than outside. High roughness of leaf canopy is responsible for high ET rates and
nearly 55% net radiation is consumed in ET.
69
Sugarcane in agriculture and industry
9 .9
EFFECT OF GREENHOUSE GASES {GHGs)
The impact of GHGs on sugarcane yield was studied by Singh and E. L. Maayar (1998). Greenhouse gases (GHGs) include CO2, nitrous oxide (N2O), tropo-spheric ozone (O3), Chlorofluorocarbons (CFCs) and methane (CH4). The anticipated rise in temperature is 1.5 to 4.5 °C with a likely mean value of 2.5 °C. Loss in cane yield is between 17 to 42% in Trinidad due to increase in temperature and soil moisture stress. There was a fall in water table due to increased ET under the warmer climate. It must be noted that air temperature increase by about 2 °C would be a major factor in yield suppression. Studies have also shown that increased CO2 concentration can increase crop yield through photosynthetic efficiency. Also increased CO2 may lead to increased stomatal resistance, decreased ET rates and increased Water Use Efficiency (WUE). However, the impact of enhanced atmospheric CO2 levels on yield improvement is contentious. The rationale is that competition from weeds may eliminate some or all benefits of increasing ambient CO2 levels on crop yields.
9 . 1 0
EFFECT OF CLIMATE ON RIPENING
Ripening is influenced by rainfall, humidity, sunshine, night length, altitude, temperature and cultivar. For effective ripening, distinct cooler nights, and dry frost free sunny days are essential. High diurnal variation in temperature is not conducive for sugar accumulation. At higher elevations in Central Africa, there were minimal diurnal variations in temperature which helped in higher sugar build up.
Ripening and maturity are influenced by the soil moisture. Better drying-off strategy maximises the sugar output. Cane yield cannot increase after the Readily Available Water (RAW) has been extracted, but sugar yield can increase substantially while the remaining soil water is extracted. In any case cane should not be allowed to extract all Plant Extractable Soil Water (PESW).
A mean dry temperature of 12-14 °C is desirable for proper ripening. At higher temperature during ripening, inversion takes place with considerably reduced sugar recoveries. Blackburn (1984) emphasises that at sea level, cane quality is a function of latitude. When sucrose content and latitude are plotted against each other,
70
9 Ecology of sugarcane
they give a bimodal curve with its nadir at the equator and peaks at 18° N and 18° S (Fig. 9.2).
The long and short of it is that the climate requirement of sugarcane is high temperature, humidity, and bright sunshine during vegetative phases but cooler nights and high light intensity for sugar build up. Note 1. RAW has been defined in terms of the irrigation requirement to maintain
stalk elongation at or above 50% of the potential. 2. PESW has been defined as the total amount of water plants can extract
prior to death.
Fig. 9.2 The influence of latitude on sucrose content of cane at harvest. Adopted from Blackburn, 1984
71
Production practices
The yield and quality of cane depend to a large extent on cultivation practices,
besides fertilizer schedules and water management. The aim of cultivation prac
tices is to prepare a fine seedbed, free from weeds and clods, yet retaining soil
moisture at rooting depth with good internal drainage. Setts should germinate
vigorously without physical hindrance. The ideal seedbed should have 5 0 % po
rosity—the pores comprising large pores (d > 10 μ), medium pores (d = 0.2-10 μ),
and fine pores (d < 0.2 μ). This condition should exist upto 60 cm soil depth.
10.1
PREPARATORY TILLAGE
The objectives of this tillage are (a) to break open soil for better aeration, (b) to
remove weeds, (c) to bury or uproot stubbles and other residues, (d) to break open
the subsoil pan, if any, (e) to drain excess water, (f) to incorporate FYM, green
manure, press mud, and gypsum, (g) to facilitate biological activity, and finally
(h) to prepare a good seedbed for p anting and facilitate cultural operations and
better water management. Land levelling which is often neglected is a must in
irrigated sugarcane farming. For water distribution and control, levelling is essen
tial. Levelling is done by a tractor operated leveller, a buck scraper, or (as is done
in subtropics) by bullock-drawn planks. In a level land, field layout is done with
the formation of ridges and furrows. Irrigation and drainage channels are also
made. In flatbed planting, levelling is important to avoid water stagnation and
poor germination.
Conventional tillage comprises primary and secondary tillage. Primary tillage
is achieved by heavy ploughs, mould board ploughs, and chisel. Ploughing should
be done at optimum soil moisture (80% field capacity). After ploughing, land is
left cloddy for weathering. A rough soil surface restricts erosion. Secondary tillage
is accompanied by working with cultivators, or tynes to break the clods. This is
followed by harrowing to achieve a fine seedbed. It must be noted that tilth is
achieved in stages by working with different implements.
In the small farms of the Godavari districts of Andhra Pradesh, crowbarring is
done instead of deep ploughing. This is done in black cotton soils to remove
Cynadon and Cyprus. Due to their cracking nature, black cotton soils are amena
ble to crowbarring.
72
10 Production practices
Presently, most of the cane fields meant for cane planting are tractor-ploughed.
Soil turning is done by mould board ploughs followed by disking or tyne harrow
ing. A rotavator is a multipurpose implement which cuts the residues, shreds
them and incorporates them into the soil in one pass.
In Hawaii and Columbia, subsoiling is done to break the hard pans. But South
African workers have convincingly demonstrated that deep subsoiling does not
guarantee a high cane yield particularly in vertisols and inceptisols. However,
Jagtap et al. (1995) reported that subsoiling is beneficial in medium black soils
which are compacted and have a tendency to waterlogging. Subsoiling loosens the
soil to a depth of 45—60 cm. Subsoiling at 2 m spacing crosswise produces the
best results by increasing the yield by 45% and sugar recovery by 1.5 units. Bulk
density is reduced with the increased infiltration rate which follows subsoiling. In
Columbia a double shank subsoiler has been developed which is locally known as
'Cenitandum'.
73
Table 1 0.1 Effect of subsoiling on yield and quality of cane grown in the soils of Warna Sugar Mill, Kolhapur with excess water and hard pan
Treatment
1. Tl—subsoiling
at 1 m spacing
2. T2—subsoiling
at 2 m spacing
3. T3—subsoiling at 2 m spacing crosswise
4. T4—control
(no subsoiling)
LSD 0.05
Yield
(t ha"1)
43-8
38.8
48.8
33.6
1.14
Pol
(%)
21.70
20.89
22.40
20.58
0.246
Bulk
density
(kg m-3)
1.380
1.384
1.396
1.538
-
Infiltration
rate
(mm hr"1)
12.40
11.20
15.40
6.60
1.438
Source: Jagtap ec al., 1995.
In most cases deep disc ploughing is required for successful cane production and the critical tillage depth is 30-45 cm, where most roots are active.
Sugarcane in agriculture and industry
In peninsular India, paddy precedes cane. The stubbles and roots of paddy (2-3 t ha-1) are incorporated in the soil. Deep ploughing is done at optimum soil moisture (80% field capacity) as the structure of the soil under wetland paddy is lost. In subtropical India, cane follows wheat and the latter's residues are incorporated in the soil by a rotavator. In sugarcane ratoons, trash is preferably decomposed in situ by applying cowdung slurry or press mud. Bioagents like Trichaderma viridae and/or Pleurotus are used to decompose recalcitrant trash.
Recent research is in favour of minimum tillage except in problem soils (salinealkali soils) and soils with hard pan. Minimum tillage implies lesser number of tillage operations than conventional tillage. In this tillage system, soil compaction is less; soil structure is not lost. Further, cultivation cost and time are saved. Zero tillage is an extreme form of minimum tillage where chemical ploughing is done by using herbicides like glyphosate or paraquat. Zero tillage is practised in developed countries like USA where labour is scarce. With all its advantages like reduced erosion and labour cost, time-saving, etc. zero tillage is not suitable for Indian conditions.
The emphasis is now on conservation tillage. It is any tillage system that reduces loss of soil and water relative to conventional tillage. Its important features are: (a) presence of crop residue mulch, (b) effective conservation of soil and water, and (c) improved soil structure and organic matter content. Stubble mulch tillage or stubble mulch farming is one of the conservation tillage systems. It is a year-round system of managing plant residue with implements that undercut residue, loosen the soil, and destroy the weeds. Sweeps or blades are generally used to cut the soil upto 15 cm depth in the first operation. A disc type implement is also used for the first operation to incorporate some of the residue in the soil. Stubble mulch tillage is difficult to carry out in sugarcane cultivation as the trash is not easily decomposed and hinders planting, watering, and other cultural operations.
According to Hudson (1995), strip tillage is adopted for sugarcane planting in stony soils. Strip tillage is defined as the concentration of tractor power to achieve thorough cultivation of only the soil area into which the crop is to be planted. The trash blanket of the previous crop is retained on the soil surface. The device cuts the trash and cultivates the soil to a depth of 30 cm. Fertilizers, chemicals, and other inputs are added only into this strip. In essence, it is precision farming or precision agriculture.
74
10 Production practices
10.2
GREEN MANURING AND APPLICATION OF BULKY MANURES
In situ incorporation of green manure crops ensures sustained cane production. Well-rotted FYM or compost at 25 t ha - 1 is mixed thoroughly in the soil. A preliminary study shows that some portion (4—5 t ha -1) can be applied to the cane rows. Green manure crops like dhiancha {Sesbania aculata) or sunn hemp {Crotalaria juncea) are grown before the cane crop and buried at the flowering stage, when it is succulent. Incorporation is done either by disc/mould board plough or rotavator. Proper soil moisture and sufficient lag before cane planting are necessary. Our experiments have revealed that intercropped sunn hemp can be incorporated followed by N-top dressing and earthing up. Thus, fertilizer use efficiency is improved.
75
Table 10.2 Average chemical composition of some organic manures and green
manure crops
Organic manures or
green manure crops
1. FYM
2. Compost
3. Average of green
manure crops
4. Mahua cake
5. Karanja cake
6. Neem cake
N
(%)
0.5-1.5
0.4-0.8
0.5-0.7
2.5-2.6
3.9-4.0
5.2-5.3
P
(%)
0.4-0.8
0.3-0.6
0.1-0.2
0.1-0.9
0.9-1.0
1.0-1.1
K
(%)
0.5-1.9
0.7-1.0
0.6-0.8
1.8-1.9
1.3-1.4
1.4-1.5
Table 10.2 presents the average chemical composition of some organic manures and green manure crops. Green manure crops like Crotolaria juncea and Sesbania aculata have 2.55—3.2% N, while the stem nodulating Sesbania rostrata has 3.2—3-37% N. Green leaf manuring can also be practised wherever available. These crops can accumulate over 200 kg N ha - 1 .
Sugarcane in agriculture and industry
1 0 . 3
SEED MATERIAL AND SEED RATE
Sugarcane is vegetatively propagated. A good seed has good sett moisture, high
invert sugars, high nitrogen content, and is free from pests and diseases. Ideally, a
heat-treated (hot water/moist air) plant crop of young age (6-8 months) is good
as seed material. A crop raised (6-8 months) exclusively for seed purpose is called
a short crop. The short crop is fertilised about 6 weeks prior to harvest, to im
prove seed quality. This is called 'prefertilising' (Humbert, 1968). The entire cane
from a short crop is fit to be used as seed material. The seed pieces with two/three
eye buds are known as setts. The entire cane should never be used as seed due to
apical dominance which hinders the germination of lower buds. Ratoon crop
should never be used as seed as it is prone to seed-borne diseases like GSD, RSD,
and smut. As a contingency plan, the top 1/3 rd portion of planted non-arrowed
cane may be used as seed. The cane meant for seed is manually harvested. Trash
and other leafy materials are removed by sickles. The cane is cut into pieces with
two/three-eye buds. By and large, two-eye bud setts are preferred. It is preferable
to plant setts immediately after cutting. Otherwise, the setts are kept in shade,
covered with trash and occasionally sprinkled with water. Drying of setts spoils
the seed quality resulting in poor germination. There are sett cutting machines
which cut 12,000 (3 or 2-eye bud) setts per hour, but some seed material is wasted.
In manual seed preparation, a sharp sickle or sharp knife is used after dipping it in
an organo-mercurial compound like Agallol or Areton. Multiple cuts and injuries
to the buds must be avoided. The young cane is placed on a wooden log and two/
three-eye bud setts are cut using a sharp knife. If the transportation of seed mate
rial is necessary, it is preferable to take the material along with trash and leaves.
Setts should be prepared at the planting place after manually stripping the leaves
and sheath.
Sett treatment to control seed-borne diseases is an important agronomic opera
tion which is neglected by farmers. The seed-borne diseases include the pineapple
disease. A 0.1 % solution (one gram in a litre of water) of an organo-mercurial
compound like Agallol or Areton or Eminan 6 is made and placed in a plastic
tub/basin and the setts are dipped in the solution for about 5 minutes. Another
systemic fungicide 'Bavistin' is also recommended. Again a 0 .1% solution is used
and the setts are dipped in the solution for 5 minutes. For one hectare about
76
10 Production practices
100 grams Bavistin dissolved in 100 litres of water may suffice. Improved germination and vigour is not only due to the control of sett-borne diseases but also due to hormonal action.
The sett rate is 30,000 three-eye bud or 50,000 two-eye bud setts per hectare— a seed rate of 6-7 t ha -1. Reduced cane yields often are due to the use of lower sett rates.
1 0 . 4
GEOMETRY OF PLANTING AND PLANTING DEPTH
A lot of research has gone into finding out the optimum spacing between rows
and within rows. The square planting or planting in the East-West direction has
no yield advantage. Usually 90,000 to 1,00,000 eye buds per ha (30,000 three- or
50,000 two-eye bud setts) are planted. Normally a well-managed crop in peninsu
lar India has 80% germination. Then the shoot population may be 72,000 to
80,000 per ha. The average tillering is taken to be 2.5 tillers per bud and the
initial shoot population comes to 1,80,000 to 2,00,000 shoots per ha. As the crop
age progresses, there may be some tiller mortality due to lack of light, water, and
genetical constraints. Finally, the number of millable canes (NMC) of the present
genotypes stands at 1,00,000 to 1,20,000 per ha or 10 to 12 per sq. m. Depend
ing on the variety, a well-fertilized and tended cane weighs about 2.0 kg. Thus the
theoretically anticipated yield is 200 to 240 t ha - 1 .
If an optimum N M C population of 10 per sq. m is maintained, any increase in
weight per cane (which is accompanied by increased height or girth or both) through
agronomic manipulation would result in yield levels of over 250 t ha - 1 .
Sugarcane evolved as a closely spaced crop but wider spacing is now necessary
due to mechanisation. The optimum spacing is 0.9 to 1.0 m between rows and the
setts are placed end to end. In subtropical India where growth is restricted due to
climatic parameters, a spacing of 0.75 m is adopted between rows. Recently, Dr. M.
Mahalingam (1999), Chairman, Shakti Sugars reported a 1.5 m spacing for cane
rows for mechanised cultivation. However, yield increase is suspect for the wider
spacing of 1.5 m as the plant density is considerably reduced, though cane weight
and girth may improve. Prudence dictates that wider spacing is essential to mecha
nise cane planting and harvesting. There is an urgent need to engineer a cane culti
var such as N C O 310 or N C O 376 which is amenable to wide spacing.
77
Sugarcane in agriculture and industry
The depth of planting should never exceed 5 cm. Moist soil of 3-6 cm depth should cover the setts to avoid drying. If heavy rains are expected, setts are placed on ridges covered with a thin layer of moist soil. The normal practice is to keep the setts in the middle of the ridge. If dry spells are anticipated, setts can be placed at the bottom of the furrow covered with a thin layer of moist soil.
1 0 . 5
PLANTING PERIOD
There is a notion among Indian farmers that cane can be planted at any time of
the year. This is not true. Warm and moist soil is desirable for germination of
buds. Soil moisture at 50-75% field capacity at 21—38 °C atmospheric tempera
ture is optimum for satisfactory sprouting of buds. There are three distinct plant
ing periods.
1) July-August (Adsali)
2) October—November (Savasali), pre-seasonal or autumn planting
3) January—March (Eksali) Suru crop
4) February—March (spring planting) in North India
Planting in July—August and October—November gives higher yield and better
quality than the planting in January-March. This is essentially due to the higher
growth period in July—August and October-November plantings.
The planting periods in different states are presented in Table 10.3.
Table 1 0 . 3 Optimum time of planting for tropical regions
State/region Season Planting time
Andhra Pradesh Adsali August-September
Eksali
Early varieties December-January
Midlate January—February
Late February—March
Gujarat Eksali January-February
Pre-seasonal October-November
contd.
78
10 Production practices
79
80
10.6
AGRONOMY OF LATE PLANTED CROP
In some areas long duration paddy and wheat precede the sugarcane crop. Due to late harvesting of paddy/wheat, late planting of sugarcane becomes inevitable. Thus planting in parts of Punjab, Haryana, and West/East Uttar Pradesh takes place in May. This late planting gives less yield as compared to the pre-seasonal (October—November) or Eksali crop (January—February). Experience has shown that late planted crop has poor stand, less tillers, suppressed growth, and is susceptible to shoot borers. Yields are poorer to the extent of 30% when compared to spring planting (February planting). The agronomy of late crop includes (a) Seeds are selected from top 1/3 rd portion of cane as regular seed is not
available. (b) Extra seeds are used and the seed rate is 8-9 t ha-1. Seeds are soaked in lime
solution/water for 2—4 hours for better germination and plant stand. Three-bud pre-germinated seeds or transplants are preferred.
10 Production practices
(c) Minimum tillage is adopted, lest soil moisture would be lost. Stubbles of previous crop of paddy/wheat are left in the field and allowed to decay in situ.
(d) Spacing is narrowed down to 60-75 cm.
(e) The crop is fertilised at 70% of the recommended dose (70—75 kg N ha -1. The fertilisers are applied as single dose before June.
(f) Trash mulch at 3.5 t ha -1 to conserve soil moisture and suppress weed growth. Recommended varieties are: Co 1148, CoJ 58, Co 1307.
(g) One or two irrigations each of 5 cm depth. (h) The crop is harvested by February-March.
1 0 . 7
PLANTING METHODS
In general there are two methods of planting, namely, manual and mechanical. In manual methods of planting, there are different types chiefly governed by soil, climatic and socio-economic conditions. Different manual methods of planting are described below.
10.7.1 Flat method of planting
This method is practised in North India. The field is ploughed once or twice with
turnings and harrowed to obtain a fine seedbed. Soil is then compacted by planking
with a wooden/stone roller. Shallow furrows, 10—15 cm deep, are opened by desi
ploughs and setts are planted end-to end. Soil is well-covered and compacted with
a log of wood. The objective is to conserve soil moisture. Due to the depletion of
soil and sett moisture, germination is slow. Irrigation does not follow immedi
ately. It is mostly a rainfed crop but receives 6—8 supplemental irrigations. Manuring
and other cultural operations are done after the South-West monsoon in June.
10.7.2 Trench or Java method of planting
This method is possible where labour is cheap. In Java (Indonesia) trenches are
manually made and soil is placed in layers after planting. It is practised in Orissa
and costal Andhra Pradesh. In trench planting, 12-15% of irrigation water is
saved due to higher retention of soil moisture. The land is well-ploughed and
trenches are made. Each trench is 25—30 cm deep and 40 cm wide. The distance
between two trenches is 90—100 cm as shown in Fig. 10.1.
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Sugarcane in agriculture and. industry
Fig. 10 .1 Trench method of planting
The bottom of the trench is loosened and 10-15 kg FYM is applied to the trench.
Cane setts are planted halfway in the trench and covered with loose, friable, moist
soil. The stalks are thick and lodging is greatly prevented and yield increase is
5-10 t ha - 1 . Furrows can be opened with a ridger and the trenches made manually.
10.7.3 Partha method of planting
This planting technique was developed by late Sir S. V. Parthasarathy for water
logged or heavy rainfall areas of coastal Andhra Pradesh, Tamil Nadu, and Karna
taka. Herein, three-bud setts are planted in a slanting position 60° to the vertical.
One eye bud is thrust into the ground about 3 cm deep and only the two top buds
germinate. Once the monsoon recedes, the in situ sprouted setts are pressed down
into the soil and made to lie horizontally. The soil from the sides is added up to
enable the shoots to strike roots. At this stage, the first dose of manure is given. In
the modified Partha method, this author attempted slant planting (45° angle) of
3-bud setts on the top of the ridge. One bud is well-positioned on the ridge and
the two top buds germinate and strike roots (Fig. 10.2).
Fig. 1 0 . 2 Modified Partha method of planting
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10.7.4 Deep trench planting
At planting
Fig. 10.3 Deep trench system for early drought and late waterlogging (Sundara, 1998)
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After full earthing up
Sugarcane in agriculture and industry
Sundara (1998) has detailed this method which is suitable in coastal Andhra Pradesh and Tamil Nadu where early droughts and late waterlogging occur. Deep trenches of 30—45 cm depth and 60 cm width are dug out manually. The spacing between the centres of two adjacent trenches is 120 cm such that the gap between the trenches is 60 cm. Sugarcane setts are planted on either side of the bottom of the trench (Fig. 10.3). Gradually, as the cane grows, the trenches are covered with soil and manure. Finally, a small trench which serves as a drainage channel is formed between the paired rows. The major advantage is that deep trench planting facilitates early germination during the drought period. But with heavy monsoon, the trench becomes a ridge and the small channel serves as a drainage outlet (Fig. 10.3). This is labour intensive. But greater number of ratoons and high yield compensate the cost of manual trench making.
10.7.5 Rayungan method or Rajoeng method of planting
Standing canes or seed stalks are decapitated (topped off) about 4—6 weeks prior to planting time. The seed stalks receive ample irrigation and fertilizers to ensure full development of rayungans on the stalk. Due to lack of apical dominance lateral shoots develop into tailed rayungans which are cut off and planted in the trenches already made. The Rayungan method of planting was developed by Dutch scientists in Java and the word is Malaysian in origin meaning sprouted bud. Rayungans are the shoots with their attached internodes severed from the mother cane or seed stalk and used for planting. The trenches with 30 cm depth are made 90 cm apart and the soil is placed in the inter-row spaces at the time of decapitating the standing cane (seed stalks). The 15 cm bottom layer of the trench is well stirred and soil is mixed with manure. Rayungans are planted vertically with a spacing of 45 cm. The rayungans planted in trenches are fertilized, manured, and irrigated. The rayungan method of planting is adopted for fast seed multiplication, especially for newly released varieties. The multiplication rate could be 100—200 times the normal seed multiplication method.
10.7.6 Seblang or sprouted bud method of planting
According to Van Dellewijn (1952) seblang method gives the highest rate of sett propagation under adverse edaphic and climatic conditions. Sprouted setts or slip setts would assure a comfortable plant stand. In this method seed crop is grown in
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light soils which are well-fertilized to promote profuse tillering. As the tiller with a root system develops, it is severed from the mother shoot and planted. The succession of tillers formed are in turn used for planting. The success of the method largely depends on the regenerative power of the plant (genetic character). The seblang method is ideal for gap filling in ratoons or in plantations with poor stand.
10.7.7 Distance planting method
In this method top setts are collected and put in the nursery. After they are sprouted and rooted, they are finally transplanted in the field at a spacing of 90 x 50 cm.
10.7.8 Al ign method of planting
This method was evolved by Dr. S. S. Singh at Allahabad Agricultural Institute and has given promising results. In this method the uppermost (last one) nodes are collected while stripping the canes for crushing or sending them to the factory. They are then planted in wheat fields in rows after every 4 rows of wheat, at a spacing of 90 cm between rows and 50 cm between plants. The planting of the nodes in the soil is followed by irrigation. The sugarcane sprouts are taken due care along with wheat. After the harvest of wheat, sugarcane is fertilised and inter sown with black gram or green gram during summer. This method saves the seed material and gives profuse tillering. It is in essence, relay cropping.
10.7.9 Tjeblock method of planting
This method is a modified version of rayungan method of planting. In this method half the length of the stalk is cut off and it is planted vertically with one node under the soil for rooting. The planted one and the mother stalks are adequately irrigated and fertilised. Now the upper buds which sprout in due course of time of both Tjeblocks and mother canes are planted by cutting them into setts as rayungans. It is to be noted that the rayungan, Tjeblock and seblang methods of planting are followed in seed nurseries to improve the multiplication rate which is low in sugarcane (10: 1 or 12: 1). These methods rarely apply to regular cane fields.
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After final earthing up
Trench systems
At planting
Fig. 1 0 . 4 Modified trench system of planting
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After final earthing up
Ridges and furrows systems
10.7.10 Modified trench system of planting
At first, ridges and furrows are opened at 120 cm spacing using tractor-drawn ridges. The furrow bottom is dug, widened, and soil is placed on the ridges. Thus the trenches are formed (Fig. 10.4). Basal manures are applied and setts are planted.
Sugarcane in agriculture and industry
At planting
As the crop grows, slight earthing up is done so that a trough is maintained throughout the crop growth period. Irrigation is given to the cane rows. According to Sundara (1998), this system is highly useful under saline water irrigated and saline soil conditions. The benefits are as much as in the ring system of planting but with much less labour. About 30% higher cane yield is obtained over the conventional ridge and furrow system. FYM or press mud application and trash mulching in this system give further improved yields. However, this author did not find any yield advantage in the alfisols of Mandya.
10.7.11 Contour system of planting
This method is adopted is undulating topography. Furrows are opened along the contours and across the slope. This helps in better water control and checks soil erosion.
10.7.12 Single bud direct planting
Single buds are directly planted in the furrows at a distance of 30 cm. Soil moisture should be adequate. This economises the expense on seed material—nearly one-third seed material is saved. Our experience has shown that the single sett should be at least 10 cm long with a healthy bud at the centre. This ensures adequate availability of food material to the germinating bud. This system of planting is referred to as Regulated Planting Technique (RPT). In the alfisols of Mandya, single bud direct planting resulted in less vigorous and low tillering stools. This was however made up without much loss in yield/quality.
10.7.13 Chip bud or bud chip technique of planting
The bud along with some portion of the internodal region is chipped by a chipping machine (Fig. 10.5). The 'bud chip' is treated with fungicide and planted in a raised bed nursery, or in polythene bags filled with FYM or press mud, soil, and sand in 1 : 1 : 1 proportions. About 6-8 weeks-old seedlings are transplanted in the main filed. In this technique there is a saving of seed (1.0 to 1.5 tons/ha would suffice) and the cane can be sent for milling after the chips are taken. Narendranath (1995) has planted transplants of bud chips raised in a nursery of 500 acres at Andhra Sugars Ltd., South Eastern India. He claims that the bud chips raised in a nursery are three times more cost effective than the conventional planting method.
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Caution needs to be exercised that bud chips are not planted directly in the main field.
Fig. 10.5 Chip-bud cutting machine
10.7.14 Pit planting
This method is prevalent in tillah lands is Assam but may be useful in the hilly tracts of Kerala (Srivastava et al., 1988). Pits at an interspacing of 25-30 cm in rows along the contours are dug with die row to row spacing of 75 cm. Organic manure is placed at the bottom of the pits. Cane setts are placed in a triangular shape in the pits and covered with moist soil. This system conserves soil and water, and is useful in rainfed agriculture.
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10.7.15 Skip-furrow planting
This system (a hybrid of the flat and trench systems) is largely followed in Orissa (Srivastava et al., 1988). Trenches are dug 45 cm apart. Setts are planted in the trenches. A gap of 90 cm is left after every two rows of cane planted at 45 cm. It saves irrigation water and facilitates spraying of pesticides and propping. While earthing, two rows are taken together, thus leaving an irrigation channel after every two rows of cane. This technique assures high stalk density.
10.7.16 Paired-row planting
This technique is known as Manjari method of planting and considerable saving in water is achieved (Fig. 10.6). Ridges and furrows are made at a distance of 60 cm and a gap of 120 cm is left after every two rows. Herein plant density per unit is maintained at 10-12 per sq. m. Setts are planted in the paired furrows. Irrigation and fertilization is done to the planted paired rows. In the skipped area, intercrops like potato or any legumes can be grown.
Table 1 0 . 4 Effect of paired-row planting on cane yield (Autumn planting, CoLk 8001)
Treatment Cane yield (t ha -1)
1989-91 1990-92 Mean
1. Conventional planting 69.3 75.3 72.3
single rows spaced 90 cm apart,
40,000 three-eye bud setts
2. Single rows spaced 90 cm apart, 71.4 80.8 76.1
80,000 three-eye bud setts
3. Paired rows (double) spaced 99.0 108.8 103.9
30 cm apart with the paired
rows 60 cm apart, 80,000
three-eye bud setts
l sd0 .05 83 6 .7 5.8
Source: Yadav et al., 1997.
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Yadav and his co-workers (1997) have tested the geometry of planting with
conventional vs paired-row autumn planted cane (CvCoLk 8001) at IISR, Luc
know. The relevant data are in Table 10.4. They have demonstrated that paired
row planting with 30 cm between rows and 60 cm between paired rows and 80,000
three-bud setts gave significantly higher yield than the conventional method of
planting. In paired rows of this type, optimum plant density is maintained. In
paired-row planting, cane gets more light and nutrients, and there is a consider
able saving in water (~25%).
At planting
Fig. 1 0 . 6 Paired row system of planting
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10.7.17 IISR 8626 method of planting
This innovative method was the brainchild of Dr. R. R. Panje and his associates. It was developed at the Indian Institute of Sugarcane Research (IISR), Lucknow. This method is suitable in subtropical India. About 2 months before planting, seed stalks are topped, removing the leaves and trash. This facilitates the sprouting of lateral buds. The cut end may be treated using a rod dipped in fungicide. Then the main field is prepared by forming trenches of 30 cm depth, 20 cm width, and spaced 90 cm apart (from centre to centre). One-third of the fertilizer dose is applied followed by digging and loosening of the trench bottom to 15 cm depth. The dug out soil is then put back into the trench along with the remaining fertilizers. Thus, the trench about 45 cm deep, is now filled with loose soil and fertilizers. Sprouted buds from the topped seed cane are used. Long 'rayungans' or 'tailed rayungans' of about 40 cm with the top side shoot intact are planted vertically in the trench at a spacing of 50-75 cm. Closer spacing is followed when plantings are late and wider spacing for early planting. The number of 'rayungans' required per ha is 20,000. Yadav (1991) claims that the IISR 8626 technique gives remarkably high yields with moderate use of fertilizers and other inputs. It is adaptable for short-season crops and intensive rotations. But it does not seem to be popular with farmers.
10.7.18 Ring planting
This method is specially suited to subtropical parts and was developed by Yadav
and his co-workers (Yadav, 1991) at IISR, Lucknow. The basic philosophy is that
mother shoots are developed and tillers are depressed. Mother shoots weigh more
with better quality. Circular pits of 90 cm diameter are dug out to a depth of
45 cm with a gap of 30 cm between two adjacent pits. Irrigation is not possible in
this system. Hence Sundara (1998) has modified the system giving a gap of 60 cm
on one side and 90 cm on the other side. (Fig. 10.7). At this spacing, about 4000
pits can be formed per hectare. The pits are refilled with loose soil and FYM or
press mud mixture to a depth of 15 cm (Fig. 10.7). While planting, 20 three-eye
bud setts per pit are planted in a circular fashion and covered with soil to a thickness
of 5 cm. Thus in each pit there are 60 eye buds and at least 40-50 mother shoots
emerge. Conversion of mother shoots to millable canes is quite high in the ring
system. Plants get good anchorage with better absorption of water and nutrients.
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Arrangement of pits in the ring system of planting
Fig. 1 0 . 7 Ring system of planting
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10 Production practices
As the crop grows soil is filled into the pits along with manure. According to some experts, this system has given a higher yield (upto 30% more than the usual) in subtropical and tropical India. This system provides better ratoons and the number of ratoons can also be increased. This is useful in saline and saline water irrigated conditions. It is also useful under trickle irrigation. Just like the deep trench system, the ring system is labour intensive. Hence this is not widely adapted in canal irrigated areas of tropical India. IISR, Lucknow has developed a 35 HP tractoroperated pit digger which can make 500 pits (90 cm diameter x 30 cm deep) per day in 8 hours.
10.7.19 Spaced transplanting technique (STP)
This technique is a modified version of IISR 8626. Single buds are used and seedlings are developed from a raised seedbed. About 6-weeks-old seedlings are transplanted in the well-prepared main field. The major advantage is saving in seed; about 2~3 tons seed per ha is required as against 8-10 t ha-1 in conventional planting. Due to synchronous tillering and uniform stalk population, better sugar recovery is anticipated. In subtropical India, 125—130 t ha-1 can be harvested. A settling nursery of 50 sq. m is enough to transplant one hectare. Small plots of 1 x 1 m are made. Well-rotted FYM is mixed well in the soil. Prior to planting of setts, Gamma BHC at 1.0 kg ha-1 is applied to the soil. Depending on the variety, 500 to 800 single bud setts can be accommodated in 1 sq. m area. Single bud setts are carefully cut and dipped in 0.1% Aretan or 0.1% Bavistin for 10 minutes. Setts are planted vertically and adequate watering is done by rose can. It has been observed that 30,000 single bed setts can be planted vertically in a 50 sq. m area. The vertically planted setts are covered with cane trash, dried leaves or any straw. Nearly 85-95% sprouting of buds takes place. When the seedlings are 4-6 weeksold, they are ready for transplanting in the main field. Seedlings are carefully uprooted and topped with a sharp knife. The seedlings are given a short dip in 0.1% solution of Areton/Bavistin.
The STP technique can be employed under both flat or trench planting. A main field is prepared as usual and basal manures are applied. A spacing of 90 cm between rows and 60 cm between transplants is recommended in the flat planting system. A hole of 15 cm depth is made with an iron bar and the setts are placed vertically. In trench planting, trenches are made 90 cm apart with a distance of
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60 cm between transplants. Gap filling is necessary and 1000 to 2000 transplants
per ha need to be replaced with new transplants from the nursery. Aftercare like
interculture, top dressing, and earthing up are done as in conventional practice.
Spot application of fertilizers is possible and N at the dose no more than 150 kg ha-1
is given in two equal splits. Higher N dose is discouraged since this leads to higher
tiller mortality.
The STP technique is suitable for seed crop or to multiply newly released vari
eties. This system has some relevance in subtropical India where adverse climatic
conditions favour poor germination and low tiller production.
10.7.20 Polybag seedling transplanting method
It is conceded that STP is labour intensive and cumbersome. The recent tech
nique of polybag seedling transplanting technique is widely acceptable. Single
buds are planted vertically in perforated plastic bags of size 10 x 15 cm filled with
FYM or press mud, soil, and sand in 1 : 1 : 1 proportion. These seedlings when
they are four to six weeks old are planted in shallow holes dug in the field, and
before doing so the plastic bags are removed. The spacing between seedlings is
30—45 cm. By this, the rate of survival is as high as 100 per cent. There is no time
lag, and the vigour of the transplants is increased by the application of an initial
fertiliser dose to supply [unreadable] 10N and P. Basal fertilisers are placed in the hole
(spot application). However, the first dose has to be applied within 10—12 days of
transplanting. The polybag seedlings are ideal for gap filling either in the plant or
ratoon crop.
Tianco (1995) has shown that 14-days-old single eye bud transplants grown in
plastic bags are planted in holes which are 1 m apart. These holes are in rows
which are apart 1 m. The required seed rate in only 0.5 t as against 6 to 7 t ha -1.
Results have shown that one seedling per hole is optimum and this registered a
1 1 % increase in cane yield. The stalk number is low, but higher stalk weight
contributes to increase in yield (Table 10.5). He anticipates better ratoon yield in
transplanting one seedling or two seedlings per hole. Further, heat treated seed
cane becomes affordable as one hectare of this planting can supply seed for 150 ha.
He has also observed that square planting facilitates intercultivation in a crisscross
direction.
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Table 10.5 Effect of planting treatments on mailable stalks, weight per stalk, and cane yield
Treatment Millable cane Weight Yield 9 month stage per stalk (t ha-1) (No. m2) (kg)
T1—one seedling per hole 6.48 1.19 77.3
T2—two seedlings per hole 6.48 1.14 73.6
T3—three one-eye bud 6.96 0.93 64.7 seed pieces per hole
T4—conventional 7.81 0.95 69.5 three-eye bud setts planted at 45° angle and covered with 5 cm soil
Source: Tianco, 1995. Yield per sq. m is converted to yield per ha.
10.7.21 Ridges and furrows method of planting
This is the most ideal cane planting system where irrigation is assured. Ridges and furrows are made by tractor-drawn or bullock-drawn ridgers. The common spacing is 90 cm. Closer spacing of 60-75 cm is desirable for early, short-durationshy tillering varieties, and in adverse conditions like moisture stress, soil and water salinity, and waterlogging. A spacing of 150 cm, which is the widest so far, is being tested under mechanised planting and harvesting. The depth of the furrow should be 25 cm. The furrow length depends on the soil type and relief. Ideally, 15-20 m furrow length is advocated in most situations. The bottom of the furrow should be loosened up to a depth 10 cm. Irrigation and drainage channels should be provided. This system is also suited to drip irrigation. Ridges and furrows provide soil aeration, anchorage, and facilitate proper earthing up. The setts are planted in the middle of the ridge to promote better germination. If three-eye bud setts are used, the middle bud is placed side wards so that all the buds are placed to the sides. There are two kinds of planting systems, dry and wet. In dry planting, buds are placed in the soil and later irrigated. In wet planting, the furrows are irrigated and then planting is done. The depth of planting is crucial for a
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Sugarcane in agriculture and industry
good stand and should be 5.0 cm. A cover of moist soil layer of about 3 cm prevents drying of setts and promotes early germination.
Fig 10.8 Ridges and furrows system
If heavy rains are expected, the setts are placed on the top of the ridge. On the other hand, if a dry spell is expected, setts are placed on the bottom of the furrow.
1 0 . 8
MECHANICAL PLANTERS
Both bullock-drawn and tractor-drawn mechanical planters have been developed by IISR, Lucknow. The bullock-drawn planter is suited for flat planting system and in light textured soils. Three persons operate this implement. One person guides the bullocks, the second person feeds the setts, and the third person guides the implement. A bullock-drawn planter can cover 1.5 ha per day at 90 cm row spacing.
An automatic tractor-drawn (35 Up) sugarcane planter has been developed at IISR, Lucknow (Sharma and Singh, 1988). The planter is an attachment to the standard hydraulically mounted tool frame with ridger bodies. The machine consists of an automatic seed cane metering mechanism, a seed chute, a Gamma BHC tank, a fertiliser application unit, a covering device, and tamping roller. The automatic metering mechanism consists of a hopper, a pusher mechanism, a weighted flap, and a picker unit. The design is such that even bent cane pieces can be metered without any problem.
It is capable of planting 3.8 ha per working day (8 hr) with four persons operating the machine.
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1 0 . 9
AFTERCARE
Sugarcane has earned a nickname as lazy man's crop, since it needs hardly any tending and care. But up to 4 months, it is intercultivated to remove weeds between the rows, create soil mulch, and aeration. Final earthing up is done during the 3.5 to 4 months stage with a ridger. In heavy black or alluvial soils the earthing up can be as high as 20-25 cm. A good earthing up prevents lodging to a great extent and facilitates application of irrigation water. Trash mulching can also be done which conserves soil moisture and smothers weeds.
Wrapping and propping is also done in intensively cultivated areas. Wrapping or trash twisting is an operation which is exactly opposite to detrashing. The dry trash is twisted around each clump in a systematic manner so that each clump appears tied up as a bundle and the green leaves are left free. With this operation, all young late shoots, borer affected ones, and uneconomical shoots are removed and only the economically millable canes are bundled up by trash-wrapping (Parthasarathy, 1972). The cheaper method of propping is trash-twisted propping. The dry leaf and trash are twisted in the form of a rope and two adjacent rows of cane are brought together and tied up at a point leaving the green leaves. This operation can be done when the height of the cane is about 1.5 m. This author has suggested that the cane rows should be in the direction of the wind and, wrapping and propping would facilitate the easy passage of gusts of wind. In general, lodging is difficult to control if the yield exceeds 100-120 t ha-1. In a strict sense, lodging in cane is a lay over. And as long as cane does not touch the ground or get broken, there will be no loss in yield or quality. Trash twisting or wrapping, propping, and earthing up are good agronomic means to contain lodging in cane.
1 0 . 1 0
MANAGING CANES UNDER STRESS CONDITIONS
Sugarcane is a long duration crop of 10 to 18 months and is grown in a variety of soils and climatic conditions. It can face abiotic stresses like waterlogging, cold, and moisture stress. A sizable cane area is under saline-alkali condition. The ger
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mination, tillering, and juvenile phases are very sensitive to these stresses. Being a
C4 plant it has a fair degree of resistance for a short period of stress. After the
relief of the stress, cane growth improves and nearly compensates the loss, pro
vided optimum inputs are given and favourable conditions prevail.
10.10.1 Cold stress
Freezing conditions occur in Iran, North India, and Pakistan. The symptoms of
chilling conditions are: sugarcane shows restricted growth, chlorosis, poor sett
germination, and lowered sprouting. Dry spells with no protective cover cause
severe frost injury. The oldest recorded cold injury comes from Cuba, where white
chlorotic bands are seen, locally called as 'manchas blanchs' or Fairs bands after its
inventor. However, varieties of Spontaneum, Sinense, and interspecific hybrids show
greater degrees of tolerance. Two well-known cold tolerant varieties are N C O 310
and CP 57-526.
Cold stress and frost injury occur at the ambient temperature of 4—8 °C. Ger
mination, tillering, and juvenile phase are more susceptible to cold stress or frost
injury. Under cold stress, roots are restricted and growth is stymied, resulting in
poor quality.
The following recommendations are made to fight cold stress or frost injury.
(a) Spring planting (January-February) is advocated. But due to uncertainty of
frost, autumn planting, i.e. October—November planting is adopted in North
West India.
(b) Trench planting is preferred to flat planting.
(c) Three-eye bud setts are recommended. It is still advisable to use transplants
grown in polythene bags.
(d) The recommended spacing is 75 cm between rows. Plant to plant distance
is 30 cm, if six-week-old seedlings are used.
(e) Irrigation is done once, before or at the onset of frost.
(f) Harvesting in February is advised.
10.10.2 Agronomy of waterlogged or excess moisture conditions
Many parts of Eastern Uttar Pradesh, North Bihar, and Deltaic regions of Tamil
Nadu face waterlogged conditions. The area under waterlogged soils in India is to
the extant of 8.5 m ha. Formative phase is more susceptible. Under waterlogged
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conditions, soil structure is lost with poor aeration. Biological activity is impaired. The redox potential of 320 mV at pH 5 is the useful dividing line between aerated (oxidised) and waterlogged soil. Plant roots under waterlogged conditons develop well-connected internal air spaces (Aerenchyma). Sugarcane under excess moisture situations exhibits stunted growth, low tillering, and chlorotic leaves. Water and nutrient absorption are reduced due to restricted root system. Adventitious roots are formed which reduce the cane quality. Cane under such situations is prone to lodging and breakage. Yield loss is due to stalk mortality. About 5-30% yield loss has been reported in situations where waterlogging occurred for 15—60 days during the late grand growth phase (Sundara, 1998). Juice is of poor quality with reduced sucrose and purity.
The best way is to open the drains at a depth of 60-90 cm and allow the water to drain. Subsurface and surface draining help to circumvent excess moisture conditions. Mole drains at a depth of 1 m are formed in heavy clay loams. If natural drainage is not possible as in low lying areas, a 'Malabar pump' or a TAS aerial flow pump (TAS—Thiru Arroran Sugars) is used to drain out excess water. The Malabar pump is known to pump out large quantities of water. Early planting is preferred in these conditions. Partha method of planting (See the section on Planting methods) can be adopted under waterlogged conditions. However, the trench method of planting is superior to other methods as shown below (Srivastava and Seth, 1990).
Planting methods Cane yield (t ha -1)
1) Flatbed planting (conventional) 54.9
2) Ridges and furrows 67.8
3) Trench planting 87.9
Higher seed rate of 7.5—9.0 t ha - 1 is used. Skip row planting with a narrow spac
ing of 60 cm between the rows and skip farrow if 1.20-1,35 m is adopted so that
the latter can act as a drainage channel. Polybag seedlings can be raised and trans
planted in the main field after the excess water recedes. All fertilizers are applied
before the waterlogging sets in. Additional N and K, and its late application is
advantageous (50 kg N + 30 kg K2O ha - 1). Hoeing controls weeds and provides
soil aeration. Detrashing and heavy earthing up prove beneficial and reduce lodg
ing, breakage, and formation of water shoots/'lalas'. Sugarcane matures early, hence
this results in an early harvest.
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The important varieties which can withstand waterlogging are: Many BO varieties, Co 62175, and Co 1148. Recent varieties recommended for excess moisture conditions of tropical India are: Co 8231, Co 8145, CoSi 86071, CoSi 776, and Co 837. Cultivars like CoTL 8201, and CoTL 88322 are grown in Thiruvalla area of Kerala where waterlogging is a common feature.
10.10.3 Moisture stress conditions
The percentage area under moisture stress conditions is increasing due to canal
closures, drying of wells and tanks, lack of adequate recharge and, late and poor
rainfall distribution. Areas under rainfed farming and water stress conditions are
confined to alluvial soils in Terai, Assam, calcareous soils in East Uttar Pradesh,
North Bihar, and coastal alluvial soils in Andhra Pradesh and Kerala. However,
these soil have good depth and better water storage. Yields are 30 -50% of nor
mally irrigated crops. The low yield is due to poor germination, lot of gaps, and
late maturity. The moisture stress crop is susceptible to early shoot borers and
scale insects. Some of the proven techniques to combat moisture stress are given
below.
(a) Autumn planting (October-November) is preferred over January-February
planting. In the Belgaum region of Karnataka, January planting is done
with one protective irrigation.
(b) Flat planting is recommended as against trench or ridges and furrow meth
ods.
(c) Spacing is narrowed down to 60—75 cm and the seed rate is 1.5 times more
than the normal (9-10 t ha -1). In the case of narrower spacing, stalk density
is higher which contributes to yield increase.
(d) Trash mulching at 5-7 t ha - 1 is a proven technology. Sundara (1998) re
ported 20% higher stalk density and 10% higher cane yield following trash
mulching. Soil temperature was also reduced by 2.1 °C under trash cover.
This has also controlled weeds.
Srivastava et al. (1988) have shown improved yield following trash mulch
(Table 10.6).
In parts of Karnataka and Tamil Nadu, under stress conditions in standing
cane lower leaves (partially dried), and trash are removed and put as mulch. The
upper 6 to 7 green leaves are left and 2% KC1 spray is administered. A late soil
application of 25 kg K2O ha -1 is done to fight drought.
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10 Production practices
Table 10.6 Effect of trash mulch on water and fertilizer use efficiency in planted sugarcane
N Without trash With trash General (kgha-1) 25 ASM 50 ASM 25 ASM 50 ASM mean
50 58.93 62.49 68.98 77.46 60.82
100 64.96 69.28 77.46 81.78 73.37
150 68.05 76.00 82.86 88.50 78.86
Mean 63-78 69.26 76.41 82.58
ASM—Available Soil Moisture Source: Srivastava et al., 1988.
If trash is affected by termites, 10% HCH dust at 25 kg ha-1 is applied. At final earthing, trash can be incorporated with the soil. Application of cowdung slurry and press mud or bioagents like Trichoderma viridae or Pleurotus sp. will hasten decomposition of trash. (e) Fertilizers—N, P2O5 and K2O at the rate of 75-25-25 kg ha-1 are applied
just before the onset of monsoon in a single dose. However, 30 kg ha-1 N can be given as a basal dose at planting and the remaining given at final earthing up.
(f) Foliar fertilization is resorted to. 2.5% urea (2.5 kg urea in 1001 water) and 2.5% KC1 (2.5 kg KC1 in 100 1 of water) are applied to cane to help fight drought. Some wetting agent like 'teepol' is added to the fertilizer solution. The volume of spray is 800—900 1 ha-1 and knapsack sprayers can be used for 3—4 months old crops. If the cane is tall (7-8 months) a wide swath boom sprayer developed by the IISR, Lucknow can be used.
(g) Setts are soaked in 0.4% lime solution (4 kg lime in 1000 1) water which is a drought hardening mechanism.
(h) If available one or two protective irrigations are beneficial. The critical stages in sugarcane are tillering and sugar accumulation phase. Alternate furrow irrigation can also be adopted. This author has tested alternatively alternate furrow irrigation. In this method one furrow is irrigated and the adjacent furrow is skipped. For the next irrigation, the skipped furrow is irrigated and the first furrow is skipped. This cycle continues. There is one-third economy in irrigation water. It also improves the yield and quality.
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A sure method of fighting drought is to use drought tolerant cultivars. These
varieties are high tillering, and have fast initial growth with a deep root system.
They can retain a leaf water potential of (Ψζ) —2.5 to 3-5 Mpa. Some of the
drought tolerant varieties are Co 8208, Co 86011, Co 85007, Co 85004, Co 7717,
CoC 90063, Co 8362, Co 87263, Co 8145, CoC 8506, and Co 6806.
10.10.4 Managing acid soils
In India acid soils are spread over an area of 4.5 m ha, where the pH is less than
5.5. The predominant characteristic of acid soil is the presence of A1 in soluble
and exchangeable forms. The input of protons (H+) and leaching of cations like
Ca, Mg, K, and Na cause acidity. The formation of acid soils depends on the
parent material, climate, topography, biological activity, and management.
It is difficult to estimate the sugarcane area under acid soils. Rough estimates
show that at least 0.5 m ha of sugarcane area is under acid soils spread over Kerala,
coastal and Malnad region of Karnataka, Goa, parts of Orissa and Assam, Terai
region of Uttar Pradesh and Bihar. Sugarcane grown in acid soils shows deficiency
of P, Ca, Mg and toxicity of Al, Mn, and Fe. Brown, short and thick roots with
less branches are the visible symptoms of cane grown in acid soils. The deficiency
of P is due to its fixation by Al. Sugarcane grown in acid soils exhibits reduced
tillering and shortened internodes with reduced yield and quality.
Liming reclaims the acid soils and the Lime Requirement (LR) is given as:
LR (meq C a C O 3 100 g-1 soil) = 1.5 x meq exch Al 100 g-1 soil.
Traditionally, LR is the amount of lime required to raise the soil pH to a certain
value, often to about 6.5. For most of the Indian soils 1-3 tons of lime applied to
plant cane would suffice depending on the soil type and management. In some
Hawaiian soils, the supply of Ca due to liming is more beneficial than the eleva
tion of pH which it causes.
The liming materials include CaCO 3 , dolomite limestone, hydrated lime, burnt
lime, blast furnace slags high in calcium silicates, and lime sludges from sugar and
paper factories. To be effective, limestone should be crushed and sieved using 100
mesh sieve (aperture 0.15 mm). Limestone coarser than 2 mm is inefficient as a
liming material.
Lime is incorporated during fallow period or prior to monsoon. It is allowed to
react with the soil for 3—4 months. The benefits of liming is more apparent in
ratoon than in plant crop. In acid soils of Assam with a pH of 5.5, Co 997 has
been successfully grown.
•JIBM&mmMM*
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10 Production practices
10.10.5 Managing saline-alkali soiis
In India saline and alkali soils are spread over an area of 5.5 m ha and 4.5 m ha
respectively and this is likely to increase due to faulty irrigation practices. Saline
soils are those with ECe more than 4.0 ds m - 1 , Exchangeable Sodium Percentage
(ESP) less than 15.0, and pH usually less than 8.5. Saline soils have been called
white alkali soils because the surface incrustation is mostly white in colour. Sugar
cane is moderately sensitive to salinity with a threshold for yield reduction at
1.7 ds m - 1 (Lingle and Weigand, 1997). Nour et al. (1989) maintained that a soil
with ECe 1.62 ds m-1 is normal. But in Egypt, sugarcane is grown in soils of ECe
ranging from 0.99 to 17.22 ds m - 1 . Sugarcane is associated with lower yields of
the order 5.45 t ha - 1 for a unit rise in ECe. Low yield is attributed to reduced
tillering, stalk density, and stalk weight. Salinity reduces internode length. Lingle
and Weigand (1997) have quantified the effect of salinity on cane yield and qual
ity. Juice molality decreased at the highest salinity. They observed that each ds m-1 increase in ECe decreased brix and pol by 0.6% and decreased apparent purity
(pol as per cent of brix) by 1.3%. Each ds m-1 increase in root zone salinity
decreased stalk population by 0.6 stalks per sq. m and the individual stalk weight
by 0.15 kg. The net loss in yield following salinity was to the tune of 13.7 t ha - 1
(op. cit.). A loss in sucrose yield is 2 t ha - 1 per ds m - 1 rise in salinity. Interestingly,
yield loss due to salinity is predictable. Salinity maps of fields generated by remote
sensing can be used to create sucrose yield maps. Understandably, a sugar quality
map would permit a sugar mill to schedule harvesting of various fields and blend
poor quality juice with high quality juice.
Saline soils are well-structured and careful leaching of salts (beyond root zone) by
good quality water would render soils very productive. Sugarcane is neither a calcifuge
(Ca-hater) nor a calcicole (Ca-lover). It is a glycophyte, growing in normal soils.
Sodic or alkali soil is difficult to manage. Sodic soils are those with pH > 8.5,
ECe <4.0, ESP > 15, and SAR > 13 to 15. Soils are dispersed with low infiltration
rate. In a field experiment in Karnal, India, Dang and his co-workers (1999)
showed variability in genotypes due to sodicity. Cane yield, sugar yield, and CCS
per cent were lowered by 9-26%, 12-29% and 3—5% respectively, with an in
crease in ESP from 14.4 to 23.5. They contend that yield loss is more pronounced
than quality following sodic environment. Early genotypes are more susceptible
to sodicity than mid or late maturing ones. Cultivar CoJ 64, an early maturing
type is most susceptible to sodicity (Table 10.7).
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Sugarcane in agriculture and industry
Table 10.7 Mean cane and sugar yields, relative yields, and CCS per cent:
early, mid, and late maturing genotypes grown in sodic and normal soils
Varietal Cane yield Relative CCS (%) Sugar yield Relagroups (t ha-1) cane (t ha-1) tive
based on yield yield maturity Sodic Normal (%) Sodic Normal Sodic Normal (%)
Early 54.8 67.8 81 14.0 14.6 7.69 9.86 78
group
Midlate 64.1 73.8 87 12.5 12.9 7.97 9.50 84
group
Late 71.5 79.8 90 11.9 12.2 8.47 9.73 87
group
Pooled 61.9 72.6 85 13.0 13.4 7.96 9.69 82 mean
Genotypes in early group: CoH 56, CoJ 64, CoH 92, CoH 99
Genotypes in midlate group: CoH 95, CoH 96, CoH 108, CoS 767
Genotypes in late group: CoH 70, Co 1148
Source: Dang et al., 1999. Data partially modified.
It was interesting to note that genotypes having a leaf Ca level of < 0.21% exhibited Ca deficiency symptoms. No deficiency symptoms were noticed in genotypes grown in normal soil. But most cane genotypes grown in sodic soil showed Ca deficiency symptoms on the younger leaves during grand growth period. The symptoms included chlorotic patches of the leaf blade which turned necrotic. Later on the leaves became wiry and curling downwards thus giving a hook-like appearance before being shed. Late maturing genotypes showed no Ca deficiency symptoms. The most susceptible genotype in the early maturing group was CoJ 64 and the most resistant in the late maturing group was CoH 70.
Reclamation measures include drainage, subsoiling, deep tillage, and replacement of Na with Ca in exchange complex. Crop rotation includes green manure crops like Dhiancha (Sesbania aculata) or stem nodulating S. rostrata and cereals like barley and paddy. Usually 2 tons of gypsum and 50 cart loads of FYM per ha would help to get reasonably good yields of cane. It has been observed that the
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10 Production practices
FYM application would not only reduce gypsum requirement but improve its efficacy.
10.10.6 Sugarcane in Tilah land and shal low black soils
Tilah lands in Assam with steep slopes are utilised for growing sugarcane. These are old alluviums with pH ranging from 4.5 to 5.5. The minimum temperature rarely goes below 12 °C and the mean temperature fluctuates between 29 and 31 °C. The annual average rainfall is around 2800 mm. Land is prepared by rabbing (burning) and is stirred with a light hoe. Planting is preferred in pits and is done in the month of April. Spacing between pits is 60 cm to reduce soil erosion. Sugarcane grown in Tillah lands of Assam shows Fe toxicity and Mn deficiency. Addition of gypsum/lime/dolomite limestone at 1 to 1.5 t ha-1 is beneficial to the cane crop. Moderate amounts of fertilizers (100-50 kg NPK ha-1) are given. Water harvesting through farm ponds would help to give 1—2 irrigations at grand growth and sugar accumulation phase respectively. Sprinkler system of irrigation is best suited but is not cost effective. Presently, the varieties grown which promise yield of about 50 t ha-1 are Co 419, Co 740, Co 997, and Co 1158. Ratoon yield is better than plant crop. Hence multiratooning in Tilah land is common.
The shallow black soils of Madhya Pradesh and Maharashtra give poor cane yield. Application of FYM and green manuring are recommended. Since the soils are calcareous, lime induced iron chlorosis is frequently met with. Soil application of sulphur at 500 kg ha-1 proves beneficial. Application of pyrites at the rate of 1 t ha-1 is cost effective. Even a single ratooning is not a distinct possibility.
10.1 1
SUGARCANE BASED CROPPING AND FARMING SYSTEMS
Crop rotations have been known for ages but J. B. Boussingault is credited with having given a scientific rotational system in 1834. He studied 5 rotations and there was a gain in all rotations except where wheat was grown.
Sugarcane based cropping system has a distinct advantage as it leaves large crop residues like trash, roots, stubbles, etc., and is also heavily fertilized. Our studies in red soils of Mandya (alfisols) have shown that paddy, cowpea, and finger millet can exploit residual fertility and give an optimum yield at 50% of the recom
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Sugarcane in agriculture and industry
mended dose. In most sugarcane growing countries some sort of rotation is followed except in Cuba, Hawaii, British Guiana, Trinidad, Fuji, and Peru where mono-cropping of cane is quite common. In Java, land tenure system enforces rotation. In Louisiana and Mauritius, cane is rotated with leguminous crops.
The ill-effects of continuous cropping as in ratooning are the build up of pests, diseases, higher soil bulk densities, and compaction. Garside and Bell (1999) believe that continuous sugarcane monoculture leads to loss in soil productive capacity or yield decline syndrome.
In India some systematic rotation is followed in sugarcane. Cane is normally rotated with rice. In Maharashtra, crop rotations are with wheat, bajra, cotton, or sorghum. As a garden crop it is rotated with potatoes, chillies, and onions. Near towns and cities, cane is rotated with vegetable crops. In North India, cane is in rotation with wheat, cotton, gram, maize, Brassica sp., sorghum, peas. In Eastern parts, rice is the usual rotational crop. Green manure crops invariably find a place in rotation with cane. In southern parts of India, cane is rotated with paddy. Soil loses tilth after rice and hence crops like groundnut/green manure crops are introduced in rotation. Short duration catch crops, specially legumes serve as a break crop. Among oil seed crops, sesame can be grown in June-July and ploughed in after 3-4 months and cane is planted, in October.
In Maharashtra, Bajra—pre-seasonal cane—ratoon 1—ratoon 2 gave the maximum returns.
The other common rotation is cotton, sugarcane, rabi jowar. In parts of Uttar Pradesh, arhar (Cajanus cajan) and groundnut are sown together with the outbreak of monsoon. Arhar is sown with an espacement of 2-7 m. In between the lines of arhar, groundnut is sown at a distance of 45 cm. Thus there will be 5 lines of groundnut between two lines of arhar. Groundnut is harvested in November and cane is planted by the trench method in February. This is in essence a relay cropping. It is worth noting that in subtropics, autumn planting (October) gives higher yield than spring planting (February-March). But due to development of high yielding varieties, cane planting gets delayed upto April.
Yadav (1991) has reported some important crop sequences in subtropical North India. (a) Rice/maize—Autumn sugarcane. Maize is harvested in September and cane
is planted in October. The yield anticipation is 78 t ha-1 and maize 2-41 ha-1. Since maize is an exhaustive crop, N dosage is enhanced.
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10 Production practices
(b) Potato—sugarcane. This sequence is followed in Punjab, Uttar Pradesh, and Bihar. Early maturing varieties are harvested to facilitate cane planting in mid March. Late potato cultivars reduce cane yield but potato yields are higher.
(c) Pigeon pea—sugarcane. If pigeon pea (cv T-21) is grown, cane is planted in spring (February-March). In Bihar, late maturing varieties of pigeon pea are taken, and cane is planted between 2 rows of pigeon pea (relay cropping). When cane starts germinating in 30—45 days, pigeon pea is harvested. In this system about 3% increased cane yield has been recorded.
(d) Mustard—sugarcane. After the harvest of mustard, cane is planted by end of March. It is quite profitable and gives about 2.8 t ha - 1 mustard and 65 t ha -1 sugarcane.
(e) Wheat—sugarcane. Consequent to the development of high yielding varieties in wheat, wheat-sugarcane rotation has become a common practice. But cane planting gets delayed upto April. Hence sugarcane needs a little tending. Normally 1/3 top portion of cane (cv Co 1148) is used as a seed material. Setts are soaked in water for 6 hr. Then setts are treated with 0.5% BHC and 0.2% agallol or 0.15% areton.
Some important crop sequences followed in India are given in Table 10.8 (Sundara, 1998).
Table 1 0 . 8 Sugarcane based cropping systems (rotations) commonly practised
in different states of India
S. No. Sugarcane based cropping systems (rotations) State
1. Rice (early)-pea-sugarcane plant-first ratoon
-wheat Eastern U.P.
2. Rice (early)-sugarcane (autumn)-first
ratoon-moong —d o—
3. Green manure-sugarcane plant-first
ratoon-wheat —d o—
4. Rice-gram/pea-green manure-sugarcane
plant-first ratoon —do-
contd.
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108
Table 10.8 contd.
S. No. Sugarcane based cropping systems (rotations) State
5. Rice-potato-sugarcane plant-first Western and ratoon-wheat Central U.P.
6. Rice-wheat/mustard-sugarcane plant-
first ratoon-wheat —do—
7. Green manure-lahi-sugarcane
plant-first ratoon-wheat —do—
8. Green manure-potato-sugarcane plant-first ratoon-wheat —do—
9. Green manure-sugarcane (autumn) + potato-ratoon-wheat —do—
10. Sorghum-gram or potato (early)-
sugarcane plant-first ratoon —do—
11. Maize (early)-potato-sugarcane-
ratoon-wheat —do—
12. Cotton + pea-sugarcane-ratoon-wheat —do—
13. Maize-wheat-sugarcane-plant-first ratoon-wheat —do—
14. Rice-pea-sugarcane-first ratoon-wheat —do—
15. Rice/maize-sugarcane-plant-ratoon —do—
16. Rice-arhar-green manure-sugarcane plant-first ratoon —do—
17. Fallow-wheat-green manure-sugarcane plant-first ratoon —do—
18. Maize-wheat-sugarcane plant-first Punjab and
ratoon-wheat western U.P.
19. Chari-berseem-sugarcane plant-first ratoon Punjab
20. Groundnut-wheat-sugarcane plant-first ratoon Gujarat
contd.
10 Production practices
Table 10.8 contd.
S. No. Sugarcane based cropping systems (rotations) State
21. Cotton-sugarcane-plant-first ratoon-sorghum Maharashtra
22. Sugarcane-plant-ratoon-wheat Maharashtra
23. Sugarcane-plant-ratoon-cotton-gram Maharashtra
24. Rice-sugarcane plant-first ratoon South India
25. Ragi-sugarcane plant-first ratoon —do—
26. Rice-groundnut-sorghum-finger millet- Karnataka under sunn hemp-sugarcane canal irrigation-
fixed 3 yr rotation
27. Sugarcane-fodder sorghum-groundnut Maharashtra -tobacco-cotton-green manure canal irrigated
areas with block system of irrigation
28. Sugarcane-plant-ratoon-kharif rice- A.P.-Telangana winter rice-sunn hemp region
Note: Autumn planting or pre-seasonal planting = Oct — Nov. Source: Sundara, 1998.
The development of short duration varieties have opened new vistas in cane culture. And of course, 3-cane crops (one plant cane, two ratoons) can be taken in 2 years which yield 8-10 t ha -1 cane or 0.8—1.0 t ha -1 sugar per month. Sundara (1987) has presented elaborate crop sequences with short duration varieties (CoA 7601). Other short duration varieties are Co 8638, Co 8641, etc. Sundara (1987) found that the rotation with short duration varieties is more profitable than the normal cane planting (Table 10.9). The cropping cycle with short duration varieties vs the normal midlate varieties is depicted in Fig. 10.9. The most profitable crop sequence was short duration plant crop—ratoon-finger millet-cotton. This system produced 195.6 t ha-1 cane, 3.8 t ha-1 finger millet and 4.07 t ha-1 seed cotton. The conventional system gave a cane yield of 203.6 t ha-1
with a B : C ratio of 2.74. The crop sequence involving short duration variety gave a net profit of Rs 48,242 ha-1 with a B : C ratio of 3.13.
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Sugarcane in agriculture and industry
110
10 Production practices
Sugarcane is well suited to agro-forestry systems. Limited experiments by this author have shown that multipurpose tree (MPTs) like Acacia albida, A. auriculiformis, Albizia falcataria, Casuarina equistifolia and Sesbania sp. can be grown in bunds or borders which act as wind breaks and prevent lodging. There is no adverse effect on yield and quality of cane following an agroforestry system. Sesbania rostrata, a stem nodulating legume serves as a green manuring crop.
111
Fig. 10.9 Cropping cycle of 24 months with short duration sugarcane or normal duration sugarcane {Source: Sundara, 1987.)
On balance, legumes are the potential candidates in sugarcane cropping system in tropical parts of Asia, Africa, and Australia. Garside and Bell (1999) concluded that well managed legume crops are best adapted to play an important role in sugarcane cropping systems. They provide nitrogen benefit to cane, have a positive effect on yield decline syndrome and enhance cash flow. They observed that both soyabean and groundnut are good cash crops and ideally fit into the sugarcane cropping system. In a plant crop, cane following soyabean produced 1.7 t ha-1 or 17% more sugar than cane—cane rotation. Moreover, soyabean contributed 300 kg N ha-1 and there is no need to apply N to plant cane.
Sugarcane in agriculture and industry
The incorporation of a green manure crop in a crop sequence has invariably led to improved yield and soil quality. Green manure crops like dhiancha, guar, cowpea, and sunn hemp add 41-71 kg N/ha (Table 10.10). Popular green leaf manure crops are Glyricidia, Karanja (Pongamia glabra) and Arak (Caiotropis gigantea) in South India. In North India potato foliage used as green leaf manure contributes nearly 30 kg N/ha. Response of cane to green manure crops ranged from 2.4 to 3.2 t ha-1.
Table 10 .10 Effect of green manure incorporation on sugarcane yield
Green N addition Mean % increase Average manure (kg ha-1) cane yield over control response of
(t ha-1) cane to N (kg)
Control 45 - -
Dhiancha 55 62 30.4 2.6
Guar 41 60 27.5 3.2
Lobia 71 68 43.0 2.8
Sunn hemp 70 67 42.8 2.9
Source: Goud, 1998.
10.11.1 Companion cropping in sugarcane
Basically in India intercropping in sugarcane is a small farmer technology, whereby the farmer gets additional income. Attempts have been made to change the geometry of planting in favour of growing intercrops. Cane is grown in paired rows 60 cm apart with 120 cm area skipped and herein the plant population is maintained. The future belongs to mechanised cultivation and willy-nilly cane is planted 60-75 cm (2-2.5 ft) apart with a skip area of 150 cm (5 ft). Preliminary observations indicate that there is no yield reduction with high tillering varieties like Co 86032. The intercropping in sugarcane is an additive series and not a replacement series. Cane is always a dominant species. Positive allelopathy has been observed in groundnut and soyabean intercropping systems.
Intercropping is common in Taiwan, Egypt, Morocco, the Philippines, and subtropical India. In Taiwan, cane is planted between every 4 rows of rice. After rice is removed, the interrows will be cultivated and plants earthed up.
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10 Production practices
113
The profits in intercropping with different intercrops have ranged from 12-34% (Lakshmikantham, 1983). In Philippines, intercropping done with groundnut provides the best returns followed by soyabean.
Some of the intercrops suitable in sugarcane are furnished in Table 10.11.
Table 1 0 . 1 1 Crops suitable as intercrops in sugarcane
A. Tropical belt (Spring planting)
Green gram Groundnut Onion
Cowpea Sesame Coriander
Black gram Sunflower Radish
Finger millet Soyabean Ladies finger
Maize
B. Subtropics (Autumn planting)
Wheat Onion Mustard Berseem
Potato Garlic Carrot Tobacco
Gram Coriander Radish Potato onion
Lentil Toria Turnip
Peas Lahi Sugarbeet Potato-wheat
Palak
C. Subtropics (Spring planting)
Green gram Tomato
Cowpea (fodder) Capsicum
Black gram Brinjal
Soyabean Dhaincha
D. Subtropics (Ratoon)
Guar, green gram (spring)
Wheat, mustard, Berseem/peas gram-autumn-ratoon
Source: Sundara, 1987.
Sugarcane in agriculture and industry
114
In tropical India, intercropping with hybrid maize, ladies finger, chillies, cotton, sorghum, and tobacco depressed cane yield. But intercrops like french beans, sunn hemp, green gram, and soyabean have proved more economical with sustained cane and sugar production (Hunsigi et al., 1995). The average of 4 intercrops resulted in the increase of cane yield to the extent of 28.8% at 200 kg N level. However, increase in yield had declined to 13 .5% and 3 .3% at 225 and 250 kg N ha -1 , respectively. Thus a clear saving of 50 kg N ha -1 is accomplished. Legumes like sunn hemp, french beans are superior to other intercrops. There was enhanced dehydrogenase activity following intercropping with legumes. Recent experiments have demonstrated that soyabean (cv. Monneta, KB 79) as an intercrop in cane is most profitable, provided the market for it is ensured.
T a b l e 1 0 . 1 2 Yield of potato and sugarcane in intercropping system in
Mauritius
S. No. Treatment Potato density Potato yield Sugar yield
(plants ha -1) (t ha -1) (t ha - 1)
1. Sole cane - - 9.95
2. One row potato/
cane interrow 7580 3.36 10.35
3. One row potato/
cane interrow 11370 6.87 9.97
4. Two rows potato/
alternate cane
interrows 15160 5.89 10.13
5. Two rows potato/
alternate cane
interrows 22740 10.76 10.05
Pooled Standard
Error 0.11 0.19
Source: Govinden, 1990.
10 Production practices
In Mauritius, intercropping of sugarcane with potato is economically viable (Govinden, 1990). Potato is planted in every interrow of plant cane and in alternate interrow of ratoon cane and is harvested before the cane canopy closes. The potato does not reduce cane yields nor does the cane reduce potato yields. The total edible energy production is 22% more in intercropping than in sole cane planting. The Land Equivalent Ratio (LER) of the intercropping system is 1.17. The farmer derives 63% more net returns from intercropping sugarcane with potato than from sole cropping of sugarcane. The yields of potato and sugarcane in intercropping systems are furnished in Table 20.12.
Govinden (1990) states that intercropping potato with sugarcane has two advantages. Firstly, rotational lands are available only in one season, whereas, intercropping can be practised in two seasons. Secondly, intercropping potato with sugarcane has reduced the effect of bacterial wilt (Pseudomonas solanacearurn).
According to Yadava (1991) intercropping in autumn planted cane is viable. Due to the slow initial growth of cane, short duration intercrops grow well and after their harvest, cane should be well manured and irrigated to have no yield reduction of sugarcane. Some important intercropping systems in subtropics for autumn planted cane are discussed below.
1. Cane + Wheat. This is the most popular system where cane is planted in mid-October and wheat by mid-November. Paired rows of cane spaced 60 cm apart are planted with a skip area of 120 cm. Three rows of wheat are taken. Sugarcane receives 150 kg N/ha, while the wheat crop receives 100-60-60 kg N, P 2O 5 , K2O per ha. Wheat should be harvested at its physiological maturity stage. After the harvest of wheat, cane should be immediately irrigated.
2. Sugarcane + Potato. This is a very profitable companion cropping system.
Two rows of potato are sown at 20 cm spacing between cane rows leaving
35 cm on both sides of potato. This facilitates better earthing up. Plant to
plant distance in potato is 20-25 cm. The variety Kufri Chandramukhi is
suitable. Potato receives a full dose of 100 kg N, 60 kg P 2 O 5 and 60 kg K2O
per ha.
3. Sugarcane + Mustard. The mustard variety Varuna (T-59) is planted along with sugarcane (cv. Co 1148/Co 1158) in the second fortnight of October. Sugarcane is spaced 90 cm apart and one row of mustard is sown with a seed rate of 4 kg ha -1 . Sugarcane receives 150 kg N in two splits, namely, 1/3 at
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Sugarcane in agriculture and industry
116
planting and the remaining top dressed after the harvest of mustard. Ferti
lizers at 60 kg N ha -1 are applied to mustard in two equal instalments, at
sowing and 30-35 days after sowing. This companion cropping results in
an yield level of 70-80 t of cane and 1.5 to 1.6 t of mustard per ha.
4. Sugarcane + Coriander. In between 90 cm rows of cane, one row of coriander is sown at 20 kg seed rate per ha. Both crops are sown in the second fortnight of October. Coriander receives 50 kg N ha - 1 , half at sowing and the other half after 3 0 - 3 5 days of sowing. The anticipated yield is 70 -80 t ha - 1 cane and 1.0 to 1.2 t of green coriander. It is averred that coriander has some bioinsecticidal properties and keeps borers at bay.
5. Sugarcane + Garlic. Local variety of garlic is used and both are planted in
the last week of October. Cane rows are spaced 90 cm apart and three rows
of garlic are sown in between cane rows. The garlic is spaced 15 cm between
rows and 10 cm between plants. Garlic is fertilized each at 30 kg NPK per
ha at sowing. The anticipated yield is 80-90 t of cane and 60-70 quintal of
garlic per ha.
6. Sugarcane + Lentils. This system is becoming popular and is economically
viable. Two rows of lentils are taken between the cane rows; both crops are
sown together in October.
T a b l e 1 0 . 1 3 Effect of intercropped legumes on yield of cane and legumes at
2 locations (t ha -1)
Legume Lucknow New Delhi
Sugarcane Intercrop Sugarcane Intercrop
Cane alone 109.4 - 50.1
Green gram 113.3 0.42 58.8 0.4
Black gram 128.8 0.51
Soyabean 102.5 1.23
Cowpea 106.3 0.51 57.5 0.45
lsd. 0.05 22.3 - NS -Source: Goud, 1998.
Sugar cane in agriculture and industry
117
Sugarcane in agriculture and industry
For spring planted cane, the important intercrops are maize, okra (lady's fin
ger), cowpea, green gram, and black gram. Sugarcane is planted 90 cm apart in
10 cm deep rows, two rows black gram (cv. P D u - 1 and T9) or green gram (cv.
pusa 101, pusa 105, P 516, K 851, jawahar 45) are sown at 30 cm distances.
Seeding depth should not be more than 5 cm. The plant to plant distance is
10 cm. Planting of cane and companion crops are taken together, i.e. February-
March. Fertilizer rates for inter crops are 20 kg N, and 60 kg P 2 0 5 per ha. Seed
rate is normally 20-25 kg ha -1. Entire NP is given to intercrops at sowing (Ta
ble 10.13).
Some important agronomic packages for autumn planted intercropped cane
are furnished in Table 10.14.
To conclude, the salient features for successful intercropping are:
1. Full dose of NPK is given to cane, 1/3 at planting and the rest as top dress
ing after the harvest of intercrop.
2. Opt imum rows of intercrops should be maintained depending on soil and
climatic conditions.
3. It is preferable to have legumes/oil seeds as intercrops.
4. The intercrops should receive full dose of NPK, preferably in two equal
splits, namely, at sowing and the other 30-50 days after sowing.
5. Soyabean seems to be more promising as an intercrop in cane at many loca
tions.
6. In more recent times lentils seem to be a promising intercrop in cane grown
under subtropical conditions.
7. Short duration varieties with open canopy as intercrops must be chosen.
Admittedly, the variety has to be tailor-made for companion cropping.
8. Immediately after the harvest of intercrop, cane should be irrigated and
fertilized.
9. A certain rotation has to be followed with a green manure or legume crop.
0.11.2 Sugarcane based farming systems
The integration of agricultural enterprises such as cropping, animal husbandry,
fishery, forestry, etc. ensures not only sustainable production but improves the
economic status of the farmer. The integration of various enterprises generates
employment and farm labour is well utilised. The farm wastes are recycled better
118
10 Production practices
in an integrated system. Any farming system is conditioned by the agro-climatic situation and socio-economic status. The farm has to be considered as a unit and effective integration of all enterprises should be planned. Sankaran and Subbiah Mudaliar (1997) have presented a rice-based farming system. The gross income was almost double and employment generation was 2.5 times more than the sole cropping system as shown below:
No. Particulars Production Labour (gross) per (man days) day per ha
1. Integrated farming system 243 1,245 (crop-poultry-fish-mushroom)
2. Control (crop) 113 573 Additional benefits 130 672
Source: Sankaran and Subbiah Mudaliar, 1997. .
The author is not aware of any sugarcane based farming system in the country or elsewhere. Suffice to say that sugarcane is well suited for a mixed enterprise since it produces a large biomass. We think that 2 ha sugarcane, 50 birds, and 4 dairy cows (crossbred) are an optimum enterprise mix. The leaves and tops serve as roughage. The press-mud is dried in two stages. In the first stage moisture is extracted by pressure and in the second stage drying is completed without overheating. Its digestibility is improved by treating with urea. The biological value of the cane tops is improved by chemical treatment with alkali (NaOH), ammonia/ urea. Sugarcane bagasse has been tried as low cost roughage in several sugarcane producing countries. The feeding value is improved by mechanical treatment (grinding), chemical treatment with urea/ammonia/NaOH and addition of substrates like molasses. Bagasse is also steamed under high pressure to improve its digestibility.
The sugarcane farming system is economically viable if enterprises like dairy and poultry are combined with it. Pretreated pith and press-mud are useful as poultry feed.
119
Sugarcane in agriculture and industry
Pla te 10.1 Cloddy soil
P l a t e 10.2 Green manuring
120
10 Production practices
121
Sugarcane in agriculture and industry
122
w Nutrition and fertiliser management
Nobel Laureate Norman Borlaug emphasised that as much as 50% of the increase in crop yields worldwide during the century is due to the use of chemical fertilisers. This is also true for a commercial crop like sugarcane. The anecdotal evidence comes from the sugarcane productivity in India during the past four decades.
Period Cane yield (t ha -1) Fertiliser (kg ha -1)
1950-51 33.4 0.55
1960-61 45.5 1.93
1970-71 53.3 13.61
1980-81 57.8 31.82
1990-91 653 69.70
During 1997—98, the consumption of fertilisers in India was 10.99 m tons N, 3.93 m tons P205> and 1.38 m tons K^O (total 16.30 m tons). Of this, the share of sugarcane was 0.92 m tons N, 0.29 m tons V2Or and 0.1 m tons K 2 0 (total 1.30 m tons). Thus, a little over 7 .5% of the total fertiliser consumption is by sugarcane. By 2025, India needs 30 m tons of NPK for food crops and 1 5 m tons of the same for commercial crops like sugarcane and cotton, etc. Approximately, 1.5 m tons of NPK will be required to produce over 400 m tons of cane. In the foregoing years the imbalance in the fertiliser usage is quite evident.
The nutrient ratio during 1997-98 was 7.95 : 2.84 : 1.0. However, the ideal nutrient ratio for sugarcane is 2 : 1 : 2. The effect of different nutrient elements on yield and quality along with the ways and means to improve the fertiliser use efficiency are presented in the following sections.
1 1 . 1
NUTRIENT UPTAKE AND REMOVAL
Sugarcane is a biomass producing crop that requires substantial quantities of inputs such as water and nutrients (Wiedenfeld, 1995). The life cycle ranges from 12 to 18 months and the cane crop removes large quantities of nutrients. Barnes (1974) has reported that a 50 ton crop will remove 34-40 kg N, 22.7 to 27.2 kg P 2 0 5 , and 68 kg KjO. Singh and Yadav (1992) showed that an average crop
124
11 Nutrition and fertiliser management
removes 208 kg N, 53 kg P, 280 kg K, 3.4 kg Fe, 1.2 kg Mn, 0.6 kg Zn and 0.2 kg Cu. In Maharashtra, Zende (1990) suggested that the crop removes 1.4 kg N, 0.6 kg P205> a fid 3.6 kg K 2 0 per ton of cane. According to him the ratio of 5 : 2 : 2 seems optimum. Under the rainfed conditions of Bihar, the uptake of N varies from 2.52 to 3.39 kg, P 2 0 5 from 0.34 to 0.65 kg, and K 2 0 from 2.30 to 4.99 kg per ton of cane (Lakshmikantham, 1983). Humbert (1968) cautions that a 100 ton crop may remove 618 kg K 2 0 ha""1 which obviously includes luxury consumption. In a recent study, Hunsigi (1993b) has shown that an average crop of 100 tons removes 205 kg N, 55 kg P, 275 kg K, 1.2 kg Fe, 1.2 kg Mn, 0.6 kg Zn, and 0.2 kg Cu. Husz (1972) has given the nutrient removal by sugarcane grown in the alfisols of Mandya as follows:
High input agriculture tends to remove large quantities of nutrients from the
soil; if the soil is not adequately fertilised it leads to mining of the nutrient re
serves of the soil.
1 1 . 2
NITROGEN
Nitrogen is a key component in the nutrition of sugarcane. Its primary function is
to increase the photosynthetic apparatus like leaf development, leaf expansion,
and tiller formation. It increases the leaf surface area and functional duration of
leaves. Sugarcane prefers N in the N 0 3 form, and also takes the N H 4 form. The
latter is subject to microbial attack that depletes N H 4 - N . Globally N application
rates range from 50—300 kg ha -1 . In Brazil, cane is grown on low N inputs, rarely
exceeding 60 kg ha - 1 for plant crop, and 80-120 kg ha - 1 for ratoons. The yield
pattern is 65-701 ha - 1 with an N uptake of 100-200 kg ha -1 (Uruiaga et al., 1992).
In the alluvial soils of Texas, USA, the plant crop receives 56 kg N ha - 1 , first
ratoon 100 to 157 kg ha - 1 , second ratoon 134-190 kg ha - 1 and subsequent ra
toons 168-202 kg ha - 1 (Wiedenfeld, 1998). Higher rates are applied to clayey
125
Sugarcane in agriculture and industry
soils than to loamy soils. But in Indian soils, N is more deficient and hence the application rates are much higher. In tropical India, N is applied at 250-300 kg ha -1. But an adsali crop receives 400 kg N ha -1. In subtropics, N application rates range from 120-150 kg ha"1, while the rainfed crops receive 60 kg ha -1. The response of irrigated cane is 0.072 to 0.035 t ha -1 kg -1 of applied N. For rainfed sugarcane the response is 0.449 t ha -1 kg -1 of N. It is evident that the better N responses are obtained at lower N rates. The All India Coordinated Project on sugarcane indicated an average response of 0.74 to 1.8 t ha"1 kg - 1 N (Yadav, 1993).
It was emphasized earlier that the response of sugarcane to applied N is almost universal and several attempts were made to express this relationship mathematically. The inverse-yield concept, Mitscherlich equation, exponential or power function, square root, and second degree polynomial equations were employed to predict the N need of sugarcane.(Hunsigi, 1993a). But the quadratic equation seems to predict the N need of cane more satisfactorily. The second order response curve for an Adsali crop is given below (Hunsigi, 1993b).
126
Yadav et al. (1997) demonstrated, that the responses and N recovery declined sharply as the N dose increased from 75 to 300 kg ha -1 to sugarcane grown in subtropical region (Table 11.1). It is to be noted that the highest response and N recovery are obtained at the lower level of N dose, i.e. 75 kg ha - 1 .
It is admitted that N recovery barely exceeds 30-40%. After application, a part is used by plants, a part remains in the soil, and the remaining is depleted through gaseous loss and leaching. Therefore, Jensssen (1998) conceived N U E (Nitrogen Use Efficiency) as a product of the uptake efficiency, i.e. U/S where U = actual uptake and S = Potential nutrient supply and utilisation sufficiency = Y/U where Y = yield, NUE = Y/S.
The rider is, S is the potential supply where the maximum quantity of the nutrient is taken up when all other nutrient and growth factors are optimum. Both Y and S depend on the availability of nutrients in relation to other growth
11 Nutrition and fertiliser management
factors and require NPK in a perfect balance to reach the maximum values. The nutrient balance concept was established by using nutrient supply equivalent, defined as the supply of nutrient that has the same effect on yield as the supply of one kg of N.
T a b l e 1 1 . 1 Effect of N levels on the cane yield response and per cent N recovery
(Cv Co. LK 8001) Mean of 2 seasons 1989-91 and 1990-92
N levels (kg ha"1)
0
75
150
225
300
lsd 05
Cane yield (t ha"1)
43.7
76.9
87.9
101.4
110.8
15.2
Response (kg cane per kgN)
—
443
294
256
224
—
N recovery
(%)
—
72.3
41.4
35.0
35.9
-
127
Sugarcane in agriculture and industry
128
Employing this formulae, this author observed that the variety Co 62175 pro
duced 60 t ha - 1 of biomass and 25 t ha -1 of CCS with an N uptake of 200 kg ha - 1 .
The RF was assumed at 0.4. The agronomic efficiency for biomass and CCS are
120 kg cane and 50 kg CCS per kg of applied N, respectively. These efficiency
figures are much higher than those reported for most crops like wheat, rice, and
triticales.
The beneficial effect of N on dry matter production/cane yield is non-conten
tious. But excessive N leads to pithiness or 'piping', water shoots (bull shoots) or
lalas, succulence of tissues, and increased incidence of pests and diseases. This
author observed that under high N fertilization and soil moisture conditions or
lack of adequate K, incidence of leaf spot disease is accentuated in the red sandy
loam soils of Mandya. Therefore, an optimum N fertilization ensures healthy
plantations. Higher N dose is not advisable from the economic and ecological
p~int of view. Hence Stanford the and Ayres (1964) have relied on the Internal N
Requirement (INR). This is defined as the average kg of N per ton of dry matter,
or kg N per kg cane. It is contended that INR is independent of N levels, location,
and variety. However, external N requirement (ENR), i.e. kg either cane, or su
crose, per kg of applied N varies to a large extent. The external N requirements of
cane grown in some important states at certain fertilizer level are given in Table 11.2.
N U E is of paramount importance to effectively utilise a costly input like nitro
gen. Efforts were made and continue to be made to improve the N U E through
agronomic means such as time and method of application and N carriers. Ranjit
and Meinzer (1997) have given convincing evidence that NUE can be improved,
and N is partitioned in favour of photosynthetic apparatus such as chlorophyll
and RUBISCO (Ribulose 1,5- biphosphate carboxylase-oxygenase). Similar ob
servations were made by Abrol and co-workers (1999). It was calculated that there
11 Nutrition and fertiliser management
is about 15% more investment in RUBISCO in wild tobacco which is absent in
transformed tobacco, resulting thereby in corresponding gain in NUE.
T a b l e 1 1 . 2 Cane yield at N levels and External N Requirement (ENR) in
different States
State N level Mean cane ENR (tons
(kg ha -1) yield (t ha) cane per kg N)
Andhra Pradesh
Maharashtra
Tamil Nadu
Punjab
Uttar Pradesh
Karnataka
Source: Hunsigi, 1993b.
A juvenile stage of a well-grown cane would have 1.9 to 2.72% N in 3—6 leaves
(index tissues).
Among the interaction, positive interactions are seen between irrigation X N,
N X P, and N X K to improve N U E of sugarcane. If water is limiting, cane cannot
take advantage of increased N availability. Wiedenfeld (1995) observed that N
uptake is relatively higher in high and medium irrigation than, in low irrigation
regimes. Similarly, P has a synergistic effect on the N uptake and yield. A com
bined application of N and P, or DAP as a basal dose improves root formation
with a consequent increased uptake of N. Positive and significant interactions
have been found between N X K. Additional potash application fights drought,
conserves soil moisture with increased uptake, and utilization of N. Likewise,
trash mulching conserves soil moisture with a concomitant improved N uptake
and yield.
11.2.1 Nitrogen losses
A fraction of nitrogen fraction is lost to environment by surface run-off, leaching,
denitrification, and N H 3 volatilisation (Ng Kee Kwong and Deville, 1995).
Chapman et al. (1994) suspected denitrification to be responsible for the loss of
129
183
295
280
187
135
250
69.41
89.17
99.05
52.36
45.70
71.38
0.38
0.30
0.35
0.28
0.34
0.25
Sugarcane in agriculture and industry
4 1 % of urea in Australia. In Hawaii, gaseous N loss ( N 2 0 ) is of the order of
30—35%. On the other hand, gaseous loss of fertiliser N was of agronomic, eco
logical and economic significance, and the highest loss of 16% at 140 kg N rate
was observed by Ng Kee Kwang et al. (1999) only at one location in Mauritius.
N (kg ha"1)
Leachate
N0 3 -N
meq 1_I
Field sample 150 200 250
0.74 0.97 1.18
Pot culture
150 200
0.90 0.95
250
0.98
Source: Shankaraiah, 1998.
The emissions of gases like N20 and N2 (Nitrous oxide and nitrogen gas) were
of the magnitude of 16 to 20 kg N ha -1 yr--1. A priori, gaseous N loss ( N 2 0 / N 2 ) is
not a major pathway of N loss which is less than 2.5% of the applied N. But the
loss of N2 gas is of significance if 80% of the soil pores were water filled for
prolonged periods (rainy season). According to them the leaching losses were no
more than 5%. However, our observations suggest that leaching losses are quite
high and even constitute 30-40% in sandy soils. A field and pot culture study
showed that the leachates may contain 0.74 to 1.18 meq I_1 NCX-N (Table 11.3).
As the applied N rate increased leaching losses were also higher.
1.2.2 N carriers
Nitrogen cycling in sugarcane is difficult to quantify. But in whatever form ap
plied N is lost from the root zone, the recovery of N is disproportionately low and
rarely exceeds 40%. Hence efforts were made to improve the recovery of applied
N through different sources of N fertilizers. The data amply demonstrated that
different N sources-like ammonium sulphate (AS), calcium ammonium nitrate
(CAN), prilled urea (PU), etc. did not improve NUE. In fact, Hartemink (1998)
asserted that the continuous use of AS decreased the soil pH from 6.5 to 5.7, and
the pH may even decrease below 5.0 which can affect sugarcane production ad
versely. Nevertheless, reducing N losses is of great importance from the ecological
130
11 Nutrition and fertiliser management
and economic point of view. Early workers had shown that yield improvement in cane by application of Telodrin and gamma B H C is due to the inhibition of nitrification. It is suspected that these chemicals have some hormonal effect. Leaching losses can be minimised by increasing the size of N fertilizer granules or by coating urea with nitrification retarding chemicals, and materials such as sulphur, shellac, neem cake, and Karanje cake. Yadav et al. (1990) observed a significant increase in N uptake by using Urea Super Granules (USG), Neemcake Coated Urea (NCU), and Dicyandiamide Coated Urea (DCU) as compared to traditional Prilled Urea (PU). They conclude that lower N recovery from PU is due to rapid volatilization and leaching losses. However, none of the N carriers have any effect on the juice quality parameters of both plant and subsequent ratoons.
Recent research is in favour of urea super granules. Srinivasan (1995) has shown
a saving of 20% N due to USG (Table 11.4)
T a b l e 1 1 . 4 Effect of urea super granules and placement of fertilizers on
sugarcane
Source. Srinivasan, 1995-
This author has field tested slow N release fertilizers like N serve treated urea,
shellac, sulphur coated urea, and urea gypsum with variable success. Another im
portant nitrification inhibitor is the oil obtained from neem {Azadirachta indicd)
which contains alkaloids like nimbin, nimbidin, and azadirachtin. At Padegoan in
Maharashtra, a saving of 100 kg N ha - 1 was reported when urea was applied with
131
Sugarcane in agriculture and industry
100 kg neem cake (Table 11.5). The impact of 100-150 kg neem cake was equiva
lent to an additional 6-81 cane per hectare. As a practical solution a physical mixture
of prilled urea and neem cake in the proportion of 5 : 1 can be mixed and used in the
cane fields. A neem cake blended urea is produced by the Maharashtra Agro Indus
tries Corporation.
400
400
300
300
300
200
200
200
lsd .05
0
140
0
96
140
0
72
150
-
Source: Zende, 1990.
I l l
118
113
115
115
109
110
110
-
170
176
164
169
172
146
151
154
11.2.3 Var ieta l response
The response to applied fertilizers depends on the inherent potential of the varieties to absorb and utilise them for the production of dry matter. The varietal effect is independent of soil type (Srinivasan, 1989). Thehighest response (0.51 t kg N_1) was observed in CoA 7602, followed by Co 6806 (0.49 t kg N"1) and Co 7201 (0.48 t kg N- 1 ) . Srinivasan (1989) concluded that from the economic and ecological point of view, it is advisable to evolve varieties like Co 6806, Co 7201, and Co 6304 which have higher production potential at both low and high input conditions, especially N.
24.1
25.4
23.1
24.1
21.1
20.7
22.2
22.2
22.3
19.54
19.80
19.70
19.74
19.53
19.30
19.75
19.90
132
11 Nutrition and fertiliser management
T a b l e 1 1 . 6 Varietal interaction with N at Mandya (Soils—alfisols, xeralfs)
Varieties CoC 671 KHS 3296
KHS 3347
Co 7708
Co 7804
Co 419
Mean
Duration early early
early
early to
midlate
midlate
midlate
-
Cane at no (tha-51
81
118
104
89
117
93
yield level l)
Naj 125 Resp< 41
31
20
24
45
22
30.5
Dplied (kg he 250
Dnse to N (t 62
73
41
42
92
52
60.3
i-1)
375 ha"1)
82 113
83
63
114
74
80.2
Mean (t ha-1) 61.7 72.3
48.0
43.0
83.7
49.3
-
Source: Hunsigi, 1993b.
The work at Mandya, Karnataka, suggested that early canes are more respon
sive to N than most of the midlate varieties, except Co 7804 which has been
recently released in Karnataka (Table 11.6). The average response was 0.241 kg N _ 1
upto 250 kg N ha - 1 and only marginally lower (0.21 t kg N - 1 ) at 375 kg N ha -1.
Wide variation (about 100%) among varieties is evident in this respect. An inter
esting finding is that varieties having comparable yield at the highest N level have
a markedly different ability to exploit soil N and thus depend on fertiliser N.
These results show that (i) a common soil test limit for all varieties is not
justified and (ii) in the case of inadequate availability of finance or fertilizer, vari
eties like KHS 3347, Co 7804, and Co 419 are much superior to others (Fig. 11.1)
(Hunsigi, 1993b).
A physiological explanation for differential response of varieties to N and N U E
is offered by Ranjit and Meinzer (1997). They observed that N U E was signifi
cantly higher in stress resistant genotype H-69-8235 than the susceptible
H 65-6052. The former genotype had greater partitioning of leaf N to chloro
phyll and RUBISCO. They conclude with optimism that it is possible to directly
manipulate the partitioning of leaf N to photosynthetic apparatus like chloro
phyll and/or RUBISCO.
133
Sugarcane in agriculture and industry
0 20 40 60 80 100 I
KHS 3296 Soil N
i i
Response to N
Co 7804 Soil N Response to N
KHS 3347 Soil N Response to N
Co 419 Soil N
Co 671 Soil N
Response to N
Response to N
Fig. 11 .1 Comparative ability of five sugarcane varieties producing comparable yield (113-201 t ha -1) to exploit soil N
11.2.4 Time and method of N appl icat ion
In order to improve NUE, the agronomic manipulation includes the proper time
and method of application. Moreover, for sustainable cane production, a high
degree of synchrony between nutrient release and plant demand is essential. In a
long duration crop like sugarcane with expansive root system, a fair degree of
synchrony can be achieved if the water supply is adequate.
A high degree of synchrony can be achieved in the intercropping system and in
cane farms with high plant densities. N is applied in two split doses. Maximum
requirement is at tillering (60 days), and grand growth phase or boom phase (120
days). A basal dose as is practised, seems irrelevant. But it is mandatory to apply N
in two equal splits, namely, at 30-45 days and 90-120 days after planting. The
data is replete to indicate that late application of N (180 days and beyond) leads
to poor cane quality, which will adversely affect sugar recovery. For early and
short duration cultivars three equal splits 30, 60, and 90 days after planting seem
optimum. For an adsali crop 4 equal splits are advocated namely 30-45 , 60-90 ,
90-120, and 150-180 days after planting.
In the Belgaum region of Karnataka, cane is planted in December/January
under residual soil moisture conditions. Experiments have shown that basal ap
plication of N at planting followed by top dressing during May-June with the
onset of monsoon improve the yield and quality of cane. Supplemental irrigations
134
11 Nutrition and fertiliser management
between December and June are also given which increase NUE. Under waterlogged conditions, as in the Tarai region of Uttar Pradesh, late N application seems inevitable. After the water is drained out, N application is possible.
Foliar application of urea or DAP to sugarcane seems contentious as the N requirement of cane is quite high; soil application is the best course. However, it can be a contingency plan, and cannot be a regular practice. This is contrary to the observations made by Srinivasan (1995).
In general, there are two methods of application, point placement and banding. Broadcasting of fertilizers should be dispensed with as this causes considerable loss of N. In point placement, pocket manuring is intended to improve NUE. Usually top dressing is done through pocket manuring and is best suited for the spaced, transplanted crop because of the distinct clumps (Sundara, 1998). Pocket manuring is the Java method of N application. In this method, 8-10 cm deep holes are dug 7—8 cm away from the clumps using sharp wooden sticks 1.0—1.5 m long. Fertiliser is placed in these holes and covered by pressing the soil. Around the clumps, 3 -4 holes are ideal.
1.2.5 The rhizosphere
The term rhizosphere (Greek rhizo = root, sphere - natural surroundings) was first
introduced in 1904 by Hiltner. It is now best defined as the volume of soil influ
enced by root activity (Hinsinger, 1998). The total rhizosphere environment is
the interacting trinity of soil, plants and organisms (Fig. 11.2). All plant nutrients
are, therefore, acquired from the rhizosphere. The rhizosphere may be up to
1-2 mm thick and the concept of rhizoplane has been envisioned. But it extends
to several centimetres in the case of nutrient and water depletion profiles.
The microbial population surrounding the root is 200 times larger than in the
bulk soil. But the root tip is typically devoid of microorganisms. The rhizosphere
affects plant growth in the following manner.
(a) Pdiizodeposition includes sugars, amino acids, vitamins and hormones.
(b) A decrease in soil pH was noticed from say 7—8 (away from the rhizosphere)
to 4—6 (in the vicinity of the rhizosphere) in many grasses including sugar
cane. This lowered pH mobilized Fe, Mn , and Zn. The intense excretion of
anions like citrate, malate, oxalate, etc. is responsible for the dissolution of
iron hydroxide. Hence an increase in the micronutrient availability can be
anticipated.
135
Sugarcane in agriculture and industry
Fig 1 1 . 2 The Rhizosphere (Arshad et al., 1998)
136
11 Nutrition and fertiliser management
(c) Production of phytosiderophores (PS) which are a group of root exudates
that exhibit strong complexation of diverse micronutrients such as Co, Cu,
Mn, Zn, and Fe. The collectively termed PS are non-proteinogenic amino
acids, mugineic acid and avenic acid, and related substances with a strong
affinity for Fe+. In addition to mobilizing Fe from calcareous soils, PS have
been shown to mobilize Cu, Mn, and Zn. In the rhizosphere undesirable
heavy metals like Co and Pb are complexed (Hinsinger, 1998). It is ob
served that graminaceae species differ widely in the qualitative and quanti
tative production of PS. Thus the species and cultigens differ accordingly in
their resistance to lime induced iron chlorosis. In essence, Hinsinger (1998)
states that biosynthesis and excretion of P complexing substances such as
phytosiderophores appear to be a 'sophisticated' strategy developed by the
graminaceous species for coping with the low solubility of naturally occur
ring Fe bearing secondary minerals (iron oxides) and for acquiring soil Fe.
(d) Root exudates are also called mucilage, a gelatinous material made of high
molecular weight polysaccharides and polyuronic acids which increase CEC
of roots. They bind heavy metals such as Pb and Cd, and micronutrients
like Cu and Zn. In acid soils Al is detoxified by massive adsorption on
mucilage. Root exudates produce special substances such as phosphatase
and phytase ecto-enzymes which help in subsequent acquisition of soil P.
This phenomenon is critical since 70—80% of the total P is present in or
ganic form.
(e) The solubility of iron oxides and iron hydroxides depends on redox condi
tions, besides soil pH. Reduction of Fe+3 occurs, and Fe+2 species rapidly
become dominant. The reduction process takes place in the rhizosphere
and can be an efficient source for higher plants to acquire and meet their Fe
nutritional demand.
(f) Another impor tant function of the rhizosphere is the production of
phytohormones or Plant Growth Regulating substances (PGRs). The PGRs
include auxins namely IAA, IBA, gibberellins, cytokinins, etc. The produc
tion of PGR in the rhizosphere is regulated by temperature, pH, soil mois
ture, nutrient availability, composition, and amount of root exudates.
(g) Plant Growth Promoting Rhizobacteria (PGPR): The term Plant Growth
Promoting Rhizobacteria (PGPR) entails all bacteria that live in plant roots
and exert a positive effect, directly or indirectly. The direct effect of PGPR
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Sugarcane in agriculture and industry
is the increased solubilization and nutrient uptake. The indirect influence is
pathogen suppression, production of siderophores, and antibiotics. The
beneficial free living rhizosphere bacteria are called PGPR and the Chinese
call it Yield Increasing Bacteria (YIB).
The PGPRs include Azotobacter, Azospirillum, Pseudomonas, Acetobacter,
Enterobacter, Xanthomonas, and Bacillus. It is well known that the PGPRs
produce growth promoting substances including auxins, gibberellins, and
cytokinins. Interestingly, A. chroococcum strain H 2 3 influenced plant growth
indirectly by enhancing the availability of phosphorus by the production of
plant growth promoting substances (PGR). There is unequivocal evidence
that Azospirillum lipaferum produces PGR in the sugarcane rhizosphere. In
acid soils (pH 3), Saccharobacter nitrocaptans is associated with the rhizosphere
of sugarcane and super rhizosphere has been visualised,
(h) The rhizosphere is implicated in the pathogenesis of plants. The poor root-
rot syndrome of sugarcane caused by Pythium graminicola may possibly be
controlled by the rhizosphere bacteria. The increased resistance of cultivar
Co 453 to Pythium root rot is attributed to the antibiotic properties of
rhizobacteria.
In today' world, conventional and intensive agricultural practices are being
challenged for both economic and environmental reasons. Sustainable agri
culture, however requires moderate consumption of fertilizers. In sum the
plant growth promoting substances (PGRs) and plant growth promoting
rhizobacteria (PGPRs) from the rhizosphere solubilize and help in acquir
ing nutrients and reduce external inputs. Metal detoxification and patho
gen attraction continue to be of central importance. This is not only envi
ronmentally friendly but also leads to sustainable cane and sugar produc
tion.
11.2.6 Nitrogen cycle in sugarcane
The N cycle in sugarcane is complex for it is highly fertilized, and leaves large crop residues. The soil N pool can be increased substantially by rotation and intercropping with legumes. Ruschel and Vose (1982) estimated an addition of 20 -63 kg N ha - 1 in plant and subsequent ratoons. The industrial wastes—vinasse (Vinhoto in Brazil)—are also added to the soil. Trash constitutes nearly 40% of the total bio-
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mass. Sugarcane trash contains about 0 .35% N, 0 .13% P2O5 and 0 .65% K 2 0 . It is composed of hemicellulose and a lot of lignin. Trash is not easily decomposed due to its recalcitrant nature.
The in situ decomposition is attained by spreading the trash in rows and sprin
kling cow dung slurry or press mud at 10 t ha - 1 . The nutritive value of trash is
debatable but it does conserve soil moisture. Ng Kee Kwong and Divelle (1987)
concluded that the contribution of trash N to sugarcane is negligible in two soil
types (Table 11.7).
T a b l e 1 1 . 7 Influence of trash (10 t ha - 1) on selected properties of two soil types at the end of a 18-month plot culture experiment
Parameters Humic Acrisol Humic Nitosol
%N
% O.M
C : N ratio
CECmeq/lOOg
AEC meq/100 g
No trash
0.14
5-5
2.2
4.1
0.7
Trash
0.16
6.7
24.3
4.2
0.6
No trash
0.18
3.2
10.2
4.4
1.1
Trash
0.19
3.8
11.6
4.9
1.0
Source: Ng Kee Kong and Divelle, 1987.
It is evident from the table that trashing contributed to organic matter build
up. However, Sundara and Tripathi (1999) assert that trash incorporation im
proves soil N status. Sugarcane trash should not be burnt. Further evidence comes
from simulation effect of trash by Vallis et al. (1996). They observed that trash
blanketing gave higher yield at all stages in which fertilizer N was used. After
about 20 years of using the trash blanket system, N fertilizer inputs may be reduced
by 40 kg N ha""1 without significant loss in yield. Leaching losses of N are also
substantially reduced.
Soil N pool can also be increased by incorporation of green manure, and the
crops include sunn hemp, dhiancha, beans, guar, barseem, pea, lathyrus (khesari).
Pongamia sp. and lentil. These crops can be grown in rotation or intercropped.
This author has found improved N status by incorporating the intercropped soya
bean (cv. Monetta, KB 79 and C o l ) . Singh and Yadav (1990) maintained that
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Sugarcane in agriculture and industry
green manuring is not only an effective fertilizer but also twice as effective as
FYM. However, the performance of green manure differs and depends on the
quantity and quality of biomass added, degree of soil improvement, and the mag
nitude of residual effect. They observed that sunn hemp contributed 4 0 - 5 0 %
towards cane yield improvement, and NUE also increased substantially. Apart
from the improved yield resulting from the use of green manuring the other ad
vantages derived from it are N2 fixation, organic matter addition, reduction in
leaching and gaseous losses, and better physico-chemical properties. The response
of green manure on cane yield was 0.243 t kg N-1 while that of FYM was
0.097 t kg N - 1 .
11.2.7 Biofertiiizers
Biological Nitrogen Fixation (BNF) has an assured place as a source of N, and
contributes to modify the fertilizer use practice. During 1997-98 India produced
more than 5000 tons of N2 fixing organisms and distributed them through differ
ent agencies. Rough estimates show that the associative diazotrophs can fix
50-100 kg N ha - 1 yr~l. Rooper and Ladha (1995) argue that the straw plus asso
ciative N9 fixers are more advantageous. Generally, callulolysis and diazotrophy
are carried out by a mixed microbial community in which the N2 fixing bacteria
utilise the products of decomposition. They demonstrated that inoculation of
straws with cellulolytic and diazotrophic microorganisms results in substantial
N2 fixation.
The free living organisms (non-symbiotic) found in the sugarcane rhizosphere
are Azotobacter, Azospirillum. Bacillus, Enterobacter, besides Acetobacter
diazotrophicus. The local population of Azotobacter/Azospirillum in cultivated tropi
cal soils is generally low. Hence inoculation through soil/sett application at
5-6 kg ha - 1 is recommended to reduce N dosage, and improve the yield and
quality of cane. The benefits of their inoculation is in the form of increased bio
mass, nutrient uptake, and yield. The production of PGR substances like IAA,
gibberellins, etc. improved water status in the plants and increased nitrate reduct
ase activity. Production of antifungal compounds have been attributed to these
microorganisms (Marwaha, 1995). It is also argued that biosynthesis of IAA by
these organisms indicates that these bacteria promote rooting, improve growth
and the metabolic process in addition to N~ fixation. Azotobacter is more suited to
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11 Nutrition and fertiliser management
semidry loamy and sandy loam soils. This requires lot of organic matter, and a significant increase in. cane yield is noticed when Azotobacter is inoculated in soil after compost is added. On the other hand , Azospirillum is an associative microaerophilic N2 fixer which fixes N in a low oxygen environment. The bacteria induce the plant roots to secrete a mucilage which creates a low oxygen environment and maintains high nitrogenase activity. Hence it is suited to clay soils. Our research amply demonstrates that Azospirillum is an effective N2 fixer in compacted ratoon soils. It is also known to maintain high nitrogenase activity (high N2 fixation) even under abiotic stress like saline-alkali conditions. It is generalised that inoculation of Azotobacter in plant crop and Azospirillum in ratoon cane ensures 12-15% increase in cane yield, besides a saving in fertiliser N up to 20—25%. These bioagents had little influence on quality parameters. Varieties showed differential response to biofertilizers (Srinivasan, 1989). Uruiga et al. (1982) gave compelling evidence that cane cultivars CB 45—3, SP-70-1143 and the Spontaneum cultivar Krakatu benefit significantly from biological N2 fixation. Among
the associative N2 fixers Acetobacter diazotrophicus contributed 170—210 kg N ha-1.
Acetobacter diazotrophicus, an endophytic bacterium is reported to be an effi
cient N2 fixer and can be established in sugarcane plants and maintained for sev
eral generations. It is called as 'black urea' and it effectively saves more than 50%
of inorganic N (Sundara, 1998). It is highly specific to sugar rich plants and has
an adaptability over a wide range of pH (3—6). It also tolerates high NO3 concen
trations up to 60-80 ppm. It can transfer more than 4 0 % of fixed N immediately
to the surrounding plant tissue. Boddey and Dobereiner (1995) contend that
under Brazilian conditions some selected endophytic bacteria of A. diazotrophicus
can be easily established in sugarcane which fix N2 up to 250 kg N ha - 1 , and can
perhaps completely replace fertilizer N. However, such claims need to be verified
under field conditions. Some recent evidence attests that A. diazotrophicus pro
duces IAA in cane cultivars. Recently, Jones (1998), Mahesh Kumar et al. (1999)
observed that this rhizobacteria is capable of releasing anions like citrate, succi
nate, tartarate, and gluconate. Thus the release of organic acids reduces the soil
pH by 1.5 units and solubilises P. Under in vitro conditions the solubilisation of
fixed P by A. diazotrophicusis in the range of 21.78 to 50.9% (loc. cit.). The effect
of diazotrophs on yield, yield components, and quality parameters of plant and
ratoon cane is presented in Tables 11.8 and 11.9.
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142
1 1 Nutrition and fertiliser management
143
Sugarcane in agriculture and industry
Tables 11.8 and 11.9 indicate an increase in the yield component with a conse
quent yield improvement. A mean yield and yield components of 4 biofertilizers
of plant and ratoon cane against control treatment is presented in Table 11.10.
Table 1 1 . 1 0 Effect of associative N2 fixers on yield, yield attributes, and quality
of ratoon cane
Treatments Cane yield Height Weight Yield incr
(t ha -1) (m) of cane ease over (kg) control
(t ha-1)
Treated
Plant cane mean of 4 168 2.71 1.61 10.0 biofertilizers
Control 158 2.55 1.52
Treated Ratoon cane mean of 4 119 2.13 1.31 4.0
biofertilizers
Control 115 2.07 1.27
Source: Shankaraiah, 1998.
Table 11.10 suggests an yield increase of 10 and 4 t ha - 1 in plant and ratoon
cane respectively. Besides, there is a saving of 50 k g N ha - 1 . However, juice quality
is not altered.
Biofertilization is highly economical since the cost of 5—10 kg ha - 1 biofertilizers
like Azotobacter, Azospirillum and Acetobacter is Rs 100 while that of 50 kg N as
urea is more than Rs 300.
11.2.8 Time and method of applying biofertilizers
Attempts were also made to study the time and method of applying biofertilizers.
The dose of 5-10 kg ha - 1 biofertilizers can be applied as a single dose at planting.
It can also be applied in two equal splits at 30 and 60 days after planting/ratoon
ing. Biofertilizers should not be applied with chemical fertilizers. The finely ground
FYM (about 500 kg) is mixed with biofertilizers and applied at the base of clumps.
As regards method of application, sett inoculation, root dipping, soil application,
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11 Nutrition and fertiliser management
smearing culture solution to single eye buds, and combinations are equally effective. However, soil application of 5 kg ha-1 biofertilizer (Azotobacter, Azospirillum or Acetobacter) in two equal splits, namely, 30 and 60 days after planting/ratooning is preferred.
1.2.9 N2 f ixers and envi ronmental p ro tec t ion
Leaching losses of NO3—N has been the major threat to groundwater pollution in high input agriculture. Nitrogenous fertilizers are the chief cause for they enter the lakes, rivers, well, and groundwater. The poor efficiency of applied fertilizers is attributed to leaching and other losses. The World Health Organisation (WHO) has classified the drinking water as very unsafe if NO3—N level is 100 mg 1-1. Our pot and field culture studies have amply demonstrated that the inoculation of Azotobacterl Azospirillum has substantially reduced the NO3—N contents of the leachates and are presented below:
1.2.10 Ex situ composting of trash and press mud (modified Japanese method)
In situ composting is ideal where the trash, 5 cm thick layers are aligned in rows and press mud, if available, at 10 t ha-1 can be spread over it. Cow dung slurry and cultures of other microorganisms at 5—6 kg ha -1 inclusive of N2 fixers and cellulolytic bacteria are thoroughly mixed. In about 8—10 weeks trash is decomposed and becomes humus. The time frame depends on the soil, climate, and management practices.
We have attempted ex-situ composting of trash. As in the Japanese method, instead of pits, vats from granite stone or slabs, bamboo and twigs are used. The slabs measure 6—10 m in length, 8—10 cm in width and have a height of 1 m. The
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Sugarcane in agriculture and industry
walls of the slabs possess holes or windows for aeration. The bottom of the vats are
covered by stone slabs and the cracks are cement plastered to prevent nutrient
losses through leaching. The cost of such a vat may range from Rs 5000 to Rs 8000
but it is just a one-time investment. If this is expensive, the vats can be made of
bamboos with the same dimensions. Stakes 1 m long are fixed at the corners to
firmly fix the vat. The ground can be plastered with clay, lime, cow dung, etc. The
structures as given by Shivashankar (1997) are shown in Fig. 11.3.
(a) Layers of biomass
(b) Compost vat fabricated from bamboo and twigs
Fig. 1 1 . 3 Ex situ composting of trash + press mud (modified Japanese method) (Source: Shivashankar, 1997.)
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11 Nutrition and fertiliser management
The first layer consists of trash 15-20 cm thick. T h e second layer consists of dried leaves, grass, and other farm residues. The press mud is sprinkled 2 -3 cm thick. Cow dung, urine, and biogas slurry can be used individually or mixed in a bucket of water and sprinkled. Copious water is added to maintain 30 -40% moisture. A small layer of soil and ash can also be maintained. T h e third layer of 10-15 cm thickness consists of green leaves of Pongamia, Albizzia, grass weeds, Dhiancha, Sesbania, and crop residues, etc. These are rich in nitrogen. The fourth layer should contain organic wastes rich in phosphates, potash such as ash, poultry wastes, etc. The fifth layer should be a few layers of straw or stover, and 5—10 cm thick trash. Lime or gypsum is added in small quantities to hasten decomposition. Two to three buckets of cow dung slurry or biogas slurry are sprinkled which should thoroughly soak the lower layers. The sixth layer should exclusively consist of 20-30 cm of cow dung. On the top of it a thin layer of fine soil, tank-silt or ash to avoid loss of moisture can be spread over. The mixed microbial culture is mixed with fine paddy straw or husk and sprinkled on the 6 th layer. A 60 cm space at one corner of the vat is left free to facilitate turning of the residues regularly. Aerobic decomposition takes place and in about 4 months the compost is ready.
Trash contains lot of lignin with little moisture. To hasten decomposition, the various microbial organisms are: Trichoderma viridae, Aspergillus, Pencillium, etc. The composite cultures like Agrobacterium, Radiobactor, Azotobactor, and Bacillus are used to enrich the compost with nitrogen. P-solubilising bacteria can be employed along with rock phosphate.
1.2.11 Vermicomposting
The importance of earthworms (Lumbricidae) has been known since Roman times,
and Charles Darwin's treatise 'The formation of vegetable mould through the
action of worms' is a classic in agricultural science. T h e importance of burrowing
activity in relation to soil drainage, aeration, and soil aggregation is well recog
nised. Hence earthworms are the true bioindicators of soil and constitute a major
soil fauna. Aptly, Radha Kale (1998) called the earthworm the Cinderella of or
ganic farming. The principal diet of earthworms consists of dead and decaying
plant remains, leaf litter, and dead roots. The N content of litter should preferably
be 1—1.4% for early action by earthworms. Litter with high polyphenols is eaten
relatively less by worms. Sugar, starches, crude protein, cellulose, and hemicellu
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Sugarcane in agriculture and industry
lose are readily decomposed. However, lignins, waxes, fat, etc. are slowly decomposed. The gut of the earthworms includes protease, lipase, amylase, cellulase, and chitinase. There are humus formers and humus feeders. The numbers commonly found in aerable soils range from 30 to 300 m - 2 and the equivalent bio-mass is 110 to 1100 kg ha-1 furrow slice.
The principal earthworm species are Perionyx excavatus, Eudrilus eugeniae and Eisenia fetida. These act on heterogenous substrates like crop residue, sugarcane trash, weeds, etc., and enhance the microbial load including N2 fixers. They also encourage the build up of cellulolytic and lignolytic microflora. Interestingly Radha Kale (1998) observed that VAM (Vesicular Arbuscur Mycorrhizae) propagules survived for 11 months in worm castings. This strongly suggests their role in the dissemination of VAM fungi.
Sugarcane is highly fertilized and leaves large residues in the form of leaves, trash, roots, stubbles, etc., and is ideal for organic farming (Hunsigi, 1997).
Fig. 11 .4 Vermary or culture room of larger dimension
Vermicomposting technology of plant residues is described below (Gangadhar and Andani Gowda, 1995) (Fig. 11.4). It is a scientific method of breeding and
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11 Nutrition and fertiliser management
rais ing ea r thworms under con t ro l l ed c o n d i t i o n s for m u l t i p l i c a t i o n . Vermicomposting is a process where earthworms are used to feed on a variety of organic wastes to produce vermicompost. Earthworms are cultured in a culture room or vermary which could be a cement tank/wooden boxes/stone lined pit or even a plastic tub of 1 m x 1 m x 0.3 m size (Fig. 11.4) or of larger dimensions.
Plants residues are placed in a separate pit. Mixing with cowdung is essential which ensures the presence of microorganisms and aids in rapid decomposition. Periodical mixing helps in proper aeration. Introduce 2000 worms of mixed population of Perionyx excavatus, Eudrilus eugeniae, and Eisenia fetida to the partially decomposed wastes in the pit. Opt imum moisture of 40—50% should be maintained. The vermicompost will be ready in 6—8 weeks. D u m p the material on the ground and keep it overnight. Sort the cocoons and young ones by hand and introduce them to the fresh tank. Thus, earthworms convert 'waste into wealth.' And the vermicompost is ready which is friable, loose, humus type with excellent manurial quality. In the vermicompost, some secretions of worms and associated microbes act as growth promoters along with other nutrients. T h e typical nutrient status of vermicompost is given in Table 11.11.
Table 11 .11 Nutrient status of vermicompost on using different organic wastes
Nutrients Per cent /ppm
Organic carbon 9.15 to 17.98%
Total N 0.5 to 1.5%
Available P 0.1 to 0 . 3 %
Available K 0.15 to 0 .56%
Available Na 0.06 to 0 .3%
Ca and Mg 22.67 to 70 meq 100 g - 1
Cu 2.0 to 9.5 ppm
Fe 2.0 to 9.3 ppm
Zn 5.7 to 11.5 ppm
Available S 12.8 to 548.0 ppm
Source: Radha Kale, 1998.
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Sugarcane in agriculture and industry
1 1.3
PHOSPHORUS
This is the second most important element in sugarcane nutrition and is impli
cated in tillering and root formation. The recovery of P is dismally low and re
stricted to 15-20%. The availability depends on the soil type, pH, and ionic
species as shown below:
The dynamics of P in soil system is presented in Fig. 11.5 (Tisdale et al., 1990). The P is lost by erosion and there is considerable chemical fixation depending on the prevalence of ionic species. At any given time the inorganic P content is more than organic P except in the organic soil.
Humbert (1968) reports that sugarcane removes 0.18-0.86 kg P2O5 per ton of cane. Nearly all tropical and subtropical soils are deficient in P but their response is highly variable. Jenssen (1998) observed that P recovery is 12% and there is room for improvement. The cumulative recovery for 2-3 ratoons could be 30— 50%, i.e. 2.5 to 4.0 times more than the recovery by plant crop. This is a strong indication of acquiring residual P by continuous cropping as in sugarcane ratoons.
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11 Nutrition and fertiliser management
Depending on soil type and management practice, P additions in India range
from 35 to 100 kg P 2 O 5 ha - 1 . The threshold soil test values for sugarcane vary
from 20-70 kg P 2 O 5 ha - 1 and the responses are likely when soil P content is
below the critical value. An effort was made to define the External P Requirement
(EPR). The EPR of sugarcane is defined as the target P concentration in soil
solution which is associated with near maximum yield. The EPR of furrow irri
gated cane is 0.005 ppm and that of the drip irrigated cane is 0.012 ppm
(Hunsigi, 1993a). The EPR is high for 3—5 months after P fertilization.
Fig 1 1 . 5 Phosphorus dynamics system in the soil (Tisdale et al., 1990)
The dose response curve to applied P followed a second degree polynomial in
many soils and for the alfisols of Mandya it is shown as: (Hunsigi, 1993a).
Y = 99.1600 + 9.2190 P - 1.0650 P2 (R = 0.945)*
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Sugarcane in agriculture and industry
The increased yield following the addition of P is ascribed to more tillers per bud and taller millable canes. P addition is accompanied by a higher percentage conversion of tillers to millable canes. In the vertisols of Maharashtra, Madhya Pradesh and Karnataka, the response of cane to P dressing is singularly absent due to high P retention (P-fixation) by these soils. A dressing of more than 400 kg P2O5 ha - 1 is required and it is a case of fertilising soil rather than fertilising the crop. The All India Coordinated Project indicated that the P response ranged from 0.09 to 1.53 t ha -1 per kg P 2O 5 at the recommended level (Yadav, 1993). No responses were observed under rainfed conditions.
Varietal differences have been noticed in respect of P response which can be related to root size, morphology and/or root physiology. Root surface area can be enhanced through mycorrhizal association. Cultivar, 86A 146 responded better to 100 kg P ha - 1 than 85 A 261. Two equal split applications (30 and 75 DAP) were better than a single application. Varietal differences are attributed to root length, root mass, and physiology of the root.
As regards the time and method of application, normally P is applied as a single dose at planting/ratooning. But in sandy loam soils it is applied in two equal splits, namely, at planting and 30-45 days after planting. The water soluble phosphates like single superphosphate are band placed in the furrow at planting. However Mussorie Rock Phosphate (MRP) is broadcast and mixed in soil. In any case the uptake efficiency is improved if P fertilizers are applied through organic carriers such as FYM, compost, dung, bagasse, press mud, etc.
11.3.1 Sources of P
As a general rule, in case of neutral and alkaline soils, water soluble P (single
superphosphate) is superior to insoluble P wherein the various water-soluble sources
are considered equally efficient. In case of acidic soils rock phosphate is the best
choice. Residual P can be as effective as freshly added P. Insoluble P like rock
phosphate can be mixed with soil and the soluble P can be placed in bands to
improve its efficiency. Additional experiments lead this author to conclude that
mixing single superphosphate and rock phosphate in equal proportions with a P
solubilizing agent improves the P-use efficiency.
Yadav (1999) compared different sources of P including the Diammonium
phosphate (DAP) and NPK complex fertilizer. The relevant data are furnished in
Table 11.12. He observed that a kg of applied P through DAP and NPK
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11 Nutrition and fertiliser management
(12 : 32 : 16) produced a maximum response of 733 kg and 985 kg respectively over control at 21.83 kg ha - 1 P application. It was 656 kg and 397 kg cane per kg P applied through single superphosphate (SSP) and Mussorie rock phosphate (MRP) at 32.75 kg/ha P application. Response decreased with increased application rate (Table 11.12).
T a b l e 1 1 . 1 2 Response (kg cane/kg applied P over control) of planted sugar
cane to phosphorus levels and different P sources at Pusa, Bihar
Treatment Cane yield Response to applied P (kg ha-1)
in control 21.83 32.75 43.66
plot (t ha-1)
1. Single super 44.5 458 656 515
phosphate (SSP)
2. Diammonium 44.5 733 687 332
phosphate (DAP)
3. NPX complex 44.5 985 977 675
fertiliser (12 : 32 : 16)
4. Mussorie rock 44.5 197 397 355
phosphate (MRP)
lsd .05 2.5
Source: Yadav, 1999.
It is inferred that N P K complex fertilizer has improved P use efficiency. The
SSP is nearly twice as efficient as MRP.
Press Mud (PM) a by-product of the sugar industry is a good source of P
besides Ca and other micronutrients. The PM obtained from carbonaceous proc
ess is alkaline in reaction. The composition is highly variable but the average
figures are: N—1.69 to 2.12 %, P—0.45 to 1.21 %, K—0.277 to 0.57 %,
Ca—1.84 to 2.38 %, Mg—0.37 to 2.29 % and S—0.6 to 0.79 %. This contains
other minor elements like Fe, Mn, Zn, and Cu in measurable quantities. The
press mud obtained from carboneous process has 1.0 % P (oven dry basis) and
can appreciably reduce the fertilizer dosage (Table 11.13).
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Sugarcane in agriculture and industry
Results in Table 11.13 indicate that 25% P can be saved by using press mud. The MRP in conjunction with SSP at equal proportion is as effective as SSP alone. The imposed treatments will not influence the quality estimates.
Table 11 .13 Cane yield as influenced by levels and sources of P
Treatment Cane yield (t ha-1) Recommended P2O5
75% 100% Mean
1.100 per cent P2O5 as single 182 182 182
single superphosphate (SSP) (19.84) (20.19) (20.01)
2.50 per cent P2O5 as SSP +
50 per cent P2O5 as 176 182 179
Mussorie rock phosphate (19.81) (20.62) (20.21)
(MRP)
3.50 percent P2O5 as SSP + 182 186 184
50 per cent P2O5 as (20.48) (20.43) (20.45)
press mud (PM)
Mean 180 183 (20.04) (20.41)
lsd .05 cane yield 3.40
lsd .05 for sucrose % NS
Recommended P level = 100 kg ha-1
Press mud contained 1% P oven dry weight basis
Figures in parenthesis indicate the percentage of sucrose in juice. Soil type—Alfisols (Xeralfs)
Source: Shankaraiah (1998).
The press mud obtained from sulphitation process (SPM) is a good source of P, S and it is known to reclaim alkaline soils (Yaduvamshi and Yadav, 1990). The application of SPM upto 30 t ha-1 in alkaline soils has reduced the soil pH, enhanced N uptake, N concentration in leaves and improved dry matter production (Table 11.14).
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11 Nutrition and fertiliser management
155
T a b l e 1 1 . 1 4 Effect of sulphitation press mud (SPM) on pH, N uptake, 3-6 N content of leaves and dry matter of planted cane
SPM Soil pH N uptake 3-6 N Dry matter treatment (1 : 2.5) (kg ha -1) content of (t ha -1)
(t ha -1) leaves (%)
0 7.84 128 1.44 26.21
10 7.67 146 1.59 27.93
20 7.52 159 1.67 28.86
30 7.49 195 1.80 29.15
Source: Yaduvamshi and Yadav, 1990
They also observed that SPM has increased stalk length and yield.
1.3.2 Phosphate Solubi l is ing Microorganisms (PSM)
Many soil microorganisms can solubilise inorganic phosphates, which are largely
unavailable to plants. Lowering of soil pH by organic acids produced by PSM
brings about the dissolution of immobile forms of P. The organic anions such as
malates, citrates, oxalates are involved in the processes in the rhizosphere includ
ing nutrient acquisition, metal detoxification, alleviation of anaerobic streams in
roots, mineral weathering (pedogenesis e.g. podzolisation) and pathogen attrac
tion (Hinsinger, 1998). Some of the hydroxy acids may chelate with Ca, Al, Fe
and Mg resulting in the effective solubilisation of P and thereby its higher utilisa
tion. The beneficial influences of artificial inoculation with PSM has been re
ported for sugarcane crop under diverse agro-climatic conditions. The descrip
tion of some P-solubilizing agents follow:
Agrobacterium radiobacter is a gram -ve rod-shaped bacteria which has a capac
ity to solubilise rock phosphate and is known to produce plant growth promoting
substances (PGR) (Gour, 1990). Bacillus megaterium var. phosphaticum is also
reported to increase the efficiency of ground rock phosphate plus superphosphate
applied to neutral to alkaline soils. In general, response to phosphobacteria is
found in soils high in organic matter and low in available P (Marwaha, 1995).
Phosphobacterial inoculation along with low grade phosphates such as rock phos
Sugarcane in agriculture and industry
156
phate, basic slag and bone meal might offer an economical alternative to the use of chemical fertilizer. Phosphobacteria apart from increasing P availability produce growth promoting auxin and gibberellin like substances. The acids produced by these microbes not only solubilise P but also Mg, Fe and Mn which contribute to the better sugarcane yield (Gour, 1990). The dissolution of P in soil contributes to enhanced P uptake by cane. The beneficial effect of phosphobacterial inoculation is also attributed to the production of PGR and to fungistatis in the rhizosphere. Aspergillus awamori renders solubilisation of rock phosphate, hydroxy apatite and tricalcium phosphate. Further confirmation comes from our experiments which suggest unequivocally the beneficial effect of PSM on cane yield and sugar output (Tables 11.15 and 11.16). This helps us to conclude that soil inoculation of Agrobacterium radiobacter or Bacillus megaterium in plant crop and Aspergillus awamori and B. megaterium in ratoon crop ensure higher cane yield, better net returns and a saving of 25 % P fertilizer (Shankaraiah, 1998). These organisms also helped in the enhanced uptake of P and K. Further, inoculation of phosphobacteria has improved quality parameters including CCS %.
Table 1 1 . 1 5 Effect of PSM on yield, yield attributes and quality estimates of
plant cane (Co 7804)
Treatments Cane Height Weight Millable Pol RS
yield (m) per cane po (%) (%)
(t ha -1) cane pulation
(kg) (103)
Agrobacterium 187 2.86 1.68 87 20.12 1.37 radiobacter
Bacillus 186 2.84 1.67 89 20.33 1.39 megaterium
Aspergillus 176 2.69 1.58 86 19.93 1.41 awamori
Control 176 2.69 1.58 90 20.52 1.33 lsd.05 4.61 0.07 0.042 .NS NS NS
Note: Each figure is a mean of single superphosphate (SSP), Missouri Rock Phosphate (MRP) and SSP plus press mud. Source: Shankaraiah, 1998.
11 Nutrition and fertiliser management
Table 11 .16 EfFect of PSM on yield, yield attributes and quality estimates of ratoon cane (Co 419)
Treatments Cane Height Weight Millable Pol RS yield (m) per cane po (%) (%) (t ha-1) cane pulation
(kg) (103)
Agrobacterium 133 2.26 1.32 104 19.20 1.17 radiobacter Bacillus 136 2.32 1.36 102 19.17 1.15 megaterium Aspergillus 137 2.34 1.36 103 19.35 1.12 awamori Control 129 2.21 1.29 102 19.35 1.10 lsd .05 5.16 0.088 0.052 NS NS NS
Note: Each figure is a mean of single superphosphate (SSP), Missouri Rock Phosphate (MRP) and SSP plus press mud Source: Shankaraiah, 1998.
In short, sett/soil inoculation of P solubilisers at 5-10 kg ha -1 improved the yield by 5—10 per cent. This was also associated with improved quality. Chhonkar (1994) tested a mixture of Pseudomonas striata and Bacillus polymyxa, commercially known as 'IARI Microphos'. Local strains were better than the exotic ones. These bioagents produced enzymes which are capable of dephosphorylating organic phosphates and also solubilise insoluble phosphates to more available forms. These perform the function of transferring P from soil into the roots. Chhonkar (1994) admits that yield increase is due to the production of PGRs and fungistatis in the rhizosphere. On balance, the future emphasis is more on the P-mobilisation than P-solubilisation. Mobilisation of nutrients like P and other nutrients is better achieved by Vesicular-Arbuscular Mycorrhizae (VAM).
11.3.3 Mycorrhizal symbiosis
Mycorrhizae involve a unique symbiotic association between plant roots and the infecting fungi. This association often increases growth and yield of many crops by enhanced nutrient uptake, resistance to drought and salinity and increased
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Sugarcane in agriculture and industry
tolerance to pathogens (Arshad and Frankenberger Jr. 1998). They are broadly classified as ecto- and endo-mycorrhizas depending on the physical relation between the fungus and the host plant root. Vesicular-arbuscular mycorrhizae (VAM) result from the colonization of young roots by fungi of the family Endogonaceae. The main genera are: Gigaspora, Glomus, Acaulospom and Scierocystis. VAM are of great importance to field crops. Following arbuscular development, structures known as vesicles develop along, or at the tips of hyphae, which function as temporary storage organs (Fig. 11.6). In reality, the hyphae are the extension of the root system and substantially increase the P acquisition by plants. Sugarcane has shown variable response to VAM (Glomus mossae; G. fasciculatus, G. fasciculatum). VAM is more effective in P deficient soils. Jones (1985) observed that C4 plants including sugarcane are VAM dependent.
Fig 11 .6 VAM structure (Brady, 1990)
The term mycorrhizosphere refers to the zone of influence of mycorrhizae (fungus root) in the soil and has two components. One is the rhizosphere, a thin layer of soil that surrounds the root and is under the joint influence of roots, root hairs and AM hyphae (Arbuscular mycorrhizae) adjacent to the root. The other is the hyphosphere which is not directly influenced by the root. The hyphosphere is in the zone of AM hyphae-soil interaction and is densely permeated by the AM soil mycelium. The extra radical hyphae can extend several centimetres into the soil and deliver fairly large amounts of nutrients, i.e. Zn, Cu besides P (Marchener,
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11 Nutrition and fertiliser management
1998). The root-free soil outside the rhizosphere is referred to as bulk soil. Depending on the physicochemical conditions of soil and management, sugarcane mycorrhizosphere may have a population of beneficial microorganisms such as N2 fixers, plant growth promoting rhizobacteria (PG PR) and phosphate solubilising bacteria. Besides improved P nutrition in mycorrhizal symbiosis, increased biomass and yield is associated with high production of PGRs. The PGRs released include IAA, GA and Cytokinin like substances (Zeatin).
Also mycorrhizal symbiosis plays an important role in maintaining cytokinin levels under drought conditions. Several studies have demonstrated increased auxin content known as 'hyper auxiny' in response to mycorrhizal infection. This indicates a positive role of auxins in the symbiosis.
It is pertinent to note that acquisition of organically bound P is enhanced by acid phosphatases released as ecto-enzymes from roots and microbes including AM fungi. Thus the activity of acid phosphatases in the rhizosphere help in P uptake.
There are clear indications of mycorrhiza mediated improvement in soil aggregation with increased number of water stable aggregates. The rhizobacterial population is involved for greater water stable aggregation.
As of now, habitable pore space will enable greater N2 fixation, pathogen control, promotion of PGRs and soil stabilization. The ultimate aim is to achieve a healthy relationship between biotic and abiotic components for sustainable sugar and cane production.
11.4
POTASSIUM
Sugarcane requires potassium in much larger amounts than any other nutrient. Its
demand may exceed 800 kg ha - 1 , albeit this includes luxury consumption. Ac
cording to Humbert (1968), a 100 ton crop on an average may remove 500 kg
K2O ha - 1 . In general, the K uptake in red, mixed red and black soils, and black
soils have ranged from about 150 to 200 kg K2O ha - 1 . A typical plant growth and
K potential relationship is shown in Fig. 11.7. An increased response is followed
by optimum K concentration to luxury consumption and toxic levels. In fact
addition of K should be at the response stage to reach an optimum level.
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Sugarcane in agriculture and industry
Fig 1 1 . 7 Plant growth and K potential relationship
The functions of potassium are many: it is required for cell structure, carbon
assimilation, photosynthesis, protein synthesis, starch formation, translocation of
proteins and sugars, entry of water into plant, and normal root development.
More than 60 enzymes are activated and it is basic to sugarcane for synthesis and
accumulation of sugar (Clements, 1980). Decreased translocation of labelled
photosynthates and increased respiratory activity in sugarcane is observed due to
K deficiency. Its role in water relation is well recognised. And late K dressing to
cane is advocated to circumvent drought conditions. Application of K is prophy
lactic measure against diseases like eye spot. Lodging in cane is greatly restricted
by K fertilization. The most important function of K in sugarcane is the improve
ment in cane quality which it affects by converting reducing sugars to recoverable
sugar and helping to flush out tissue N and moisture. In general, improvement in
yield following K addition is reflected by improvement in pol (sucrose) per cent
cane. Thus, adequate K is required to utilize the assimilated N in cane to bring a
stage of maturity when reducing sugars are converted to recoverable sugar. But
deficiency of K is seen in older leaves first as it is highly mobile in the plant. Leaf
emergence and tips become brown with necrotic spots which coalesce and show
typical 'marginal firing' under severe K deficiency.
11.4.1 Forms of potassium
Four forms of soil K are recognised as regards its availability to plants. They are:
structural (matrix), non-exchangeable (not easily available), exchangeable, and
solution K which are all in equilibrium with each other (Fig. 11.8b). Figure 11.8a
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11 Nutrition and fertiliser management
shows the position of K on the clay mineral. The K on the planar and edges are easily exchanged with solution K. The interlattice K is the fixed K. Despite K fixation, K recovery is to the extent of 80% by sugar cane.
Fig 1 1 . 8 a Exchange position of K on clay mineral
Fig 1 1 . 8 b Interrelationships of various forms of soil K
In reality the agricultural soils are nearly always in a state of disequilibrium
with regard to K transformation, more so the sugarcane soils which are intensively
cropped and heavily fertilized. The interrelationship of various forms of soil K
and the fate of fertilizer K are shown in Fig. 11.9. It may be noted that apart from
plant uptake, K is subject to intense leaching.
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Sugarcane in agriculture and industry
Fig 1 1 . 9 Different forms of soil potassium
11.4.2 Soil K extractants
The extractants for soil K have ranged from a large array of buffer solutions, acids,
percolation techniques, exchange resins to Electro Ultra Filtration (EUF) and
potash potential (Hunsigi and Srivastava, 1976). For more than three decades,
neutral normal ammonium acetate (N, N H 4 OAC, pH 7) has been widely ac
cepted as a measure of exchangeable soil K and for sugarcane 100-125 ppm ex
changeable K has been taken as a critical limit. However, this author asserts based
on experimental evidence, that exchangeable K per se is not a good indicator of K
supply to long duration crops like sugarcane/ratoons (Hunsigi and Srivastava,
1981). For routine soil testing, extraction with cone. H 2 S O 4 predicts K availabil
ity better than N, NH 4 OAC (pH 7). Thus the critical limit under cone. H 2 S O 4
extraction is 300 ppm. A detailed investigation by this author led him to conclude
that a portion of non-exchangeable K but plant available form known as 'step PC
predicts better K availability to plant or ratoon cane (op. cit.). Wild (1988) reaf
firmed that the prediction of K availability is improved by the inclusion of readily
released non-exchangeable K. Out of the chemicals tested, sodium tetraphenyl
boron (NaTPB), a specific K extractant is better suited, for it seems to simulate
the mechanism of plant removal in a more rational manner. But this chemical is
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11 Nutrition and fertiliser management
not cost effective. Continuous extraction in boiling H N O 3 has a drastic action
besides introducing large analytical errors. T h e constant rate K(CRK) under con
tinuous boiling H N O 3 extraction reflects the structural or matrix K (Hunsigi and
Srinivasa, 1981). The equilibrium activity ratio (ARoK) and potash chemical po
tential (ΔGoK) are good indices of K availability to sugarcane but can hardly be
used in large-scale soil testing. A nomogram based on six methods of measuring K
supply power to sugarcane has been presented elsewhere (op. cit.).
11.4.3 Source, method and t ime of K appl icat ion
All sources of K are equally effective. Potassium scheonite (24% K 2O) is as good
as muriate or sulphate of potash (Hunsigi, 1993a). Potash is band placed in the
cane furrows below the set but 3—5 cm away from it. Point placement/spot appli
cation is preferred in ratoons where stools are distinct. As regards time of applica
tion, it is mostly given as a single basal application. However, split application is
advisable in very sandy soils. T h e recommended time of application in different
crop and soil situations is given in Table 11.17.
T a b l e 1 1 . 1 7 Time of K application to sugarcane
Single basal application for Two equal splits, namely, planting
and 60 DAP for
1. Ratoons (stubble Low tillering varieties and Cvs with
root is restricted) low initial vigour
2. Medium black and black Loamy sands and sandy loam soils
soils with high C E C
3. Early maturing short Late maturing and non-flowering canes
duration and drought
tolerant CVs
Late K application (6 months) under
moisture stress condition
11.4.4 Rate of K appl icat ion and response studies
Almost all soil types responded to K addition including the alluvial soils of Indo
Gangetic plains which contain K bearing minerals like illite and micas (Yadav,
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Sugarcane in agriculture and industry
1999). Increased tonnage following K addition was observed more in red, mixed
red and black soils and black soils of peninsular India. Agronomic value of K rests
with improved girth and volume of cane (Cane volume V = P x L x D x 3/4; L =
cane length, D = cane diameter). The application rates have ranged from 50 to
200 kg ICO ha - 1 , depending on soil type and agroecological situations. The re
sponse varies from 0.01 to 0.352 t ha - 1 per kg K2O. Under rainfed conditions, K
response was around 0.27 t ha -1 per kg KjO (loc. cit.). Potash yield relationship
can be better explained by the second degree polynomial or modified Mitscherlich
equation. Many field studies in peninsular India support the contention that re
sponse of cane applied K can be better predicted by a second degree polynomial
(Table 11.18). Further optimum K index (3-6 leaf sheaths) should be maintained
at 2.25% under better level or management (Clements, 1980). Since all K in cane
is dissolved in cell sap, K - H 2 O index (i.e. K content of 3—6 leaf sheaths expressed
as per cent sheath moisture) is envisioned.
T a b l e 1 1 . 1 8 Some potassium response equations in sugarcane
Region Soil Crop/ Quadratic equation
type variety
Mandya Red Plant crop = 154.012 + 0.0315 K- 0.0004K2
soil Co 419
Sankeshwar Black Plant crop = 139.96 + 0.2400 K- 0.00179 K2
soil Co 740
Anakapalle - Plant crop = 78.9760 + 0.0452 K- 0.0061 K2
Co 419
Cuddalore Alluvial Plant crop = 91.12 - 0.1850 K- 0.00041 K2
soil Co 658
Source: Srivastava and Hunsigi, 1978.
11.4.5 Response to NPK ferti l izers
Sugarcane requires 3.71 to 5.23 kg of NPK per ton of millable cane. The nutrient requirement of cane is maximum for K followed by N and P. Admittedly, emerging deficiency of P, S, and micronutrients in cane may limit the efficiency of other nutrients. The positive interactions between N x K, N x P and N x P x K support
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11 Nutrition and fertiliser management
this contention and call for adequate dressing of NPK. The relative cane yield as
influenced by NPK levels is shown in Fig. 11.10. Highest response was observed
in N followed by P and K in red soils (alfisols) of Mandya. Our survey in the
farmers' fields of Karnataka has revealed that there is a great imbalance in favour
of N application. Also due to the cost factor, P and K applications are totally
dispensed with or inadequately dressed. The recommended NPK dose ranges from
120-40-50 to 250-50-100 kg ha - 1 (Adsdi crop 400-50-100 kg ha -1). The yield
yardstick at the recommended dose is 52 to 218 kg cane per kg of NPK (Yadav,
1999). Table 11.19 shows the recommended fertilizer dosage in different parts of
the country (TIFAC, 1991).
165
Fig 1 1 . 1 0 Relative cane yield (plant crop) as influenced by NPK levels
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Sugarcane in agriculture and industry
There is a tendency among the sugarcane farmers, particularly in peninsular
India to apply more fertilizers (specially N) than the recommended dose. Obvi
ously this is not economical and leads to reduced profits. Hence NPK recommen
dations have been given to the target yield (Table 11.20). Yadav (1999) provided
convincing evidence that target yield could be achieved within 8% variation with
fertilizers applied on soil test basis. It stands to reason that application of NPK on
soil test basis rather than the general recommendation gives higher yield response
and better benefit: cost ratio (B : C ratios).
Table 1 1 . 1 9 Recommended fertilizer dosage for sugarcane in different parts
of the country
S. State/region Situation/crop Dosage (kg ha -1)
No. N P2O2 K2O
1. Andhra Pradesh Coastal region - - -
Srikakulam and Visakhapatnam - 112 -
East Godavari and
Krishna Eksali 168 - -
West Godavari Eksali 168 - -
Rayalaseema region Eksali 224 - -
Telangana and Medak Eksali 112 - -
Nizamabad Eksali 250
Adsali 400
2. Assam Spring 130 60 60
3. Bihar- Moderately
northern region irrigated 90 70 30
Adequately 90 70 30
irrigated
Trench 170 85 130
planted
contd.
11 Nutrition and fertiliser management
T a b l e 1 1 . 1 9 contd.
S. State/region Situation/crop Dosage (kg ha-1)
No. N P 2 O 2 K2O
4. Gujarat Eksali 250 125 125
5. Haryana Jagadhri Spring 150 50 -
tehsil and Ladwa block planted
Other areas Spring 150 - -
planted
irrigated
6. Karnataka Eksali 250 75 125
Mandya region
Tungabhadra Adsali 250 75 75
project and
Bhadra area
Belgaum area Eksali 250 75 185
Heavy rainfall areas Eksali 187 125 125
7. Kerala Eksali 165 80 80
Pandalam and
Thiruvalla areas
Chittoor area Eksali 225 75 75
8. Madhya Pradesh Spring 300 80 45
planted
9. Maharashtra Adsali 400 170 170
Deccan canal region Pre-seasonal 340 170 170
Vidharbhaand Pre-seasonal 250 170 170
Marathwada region
Deccan canal region Suru (Eksali) 250 115 115
Vidharbha a n d Suru (Eksali) 170 115 115
contd.
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Table 11.19 contd.
S. State/region Situation/crop Dosage (kg ha -1)
No. N P2O2 K2O
Marathwada region
Konkan region Sum (Eksali) 150 110 110
10. Orissa Spring 220 100 60
11. Punjab Spring 150 -
planted
Autumn 225 - -
planted
12. Rajasthan
Northern region Spring 150 - -
South eastern region planted 150 - -
Southern and 170 - -
central-eastern region
13. Tamil Nadu
Coastal belt Eksali 275 62 112
Canal irrigated areas - 275 62 112
Lift irrigated areas - 225 62 112
Jaggery areas - 175 62 112
14. Uttar Pradesh Spring 150 -
planted
Autumn 180 -
planted
15. West Bengal Spring 160 60 60
planted
Source: TIFAC (1991) "Sugarcane Cultivation and Sugar Production Technologies" P. 20-28.
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11 Nutrition and fertiliser management
Table 1 1 . 2 0 Nutrient requirement for targeted yield
Target yield Nutrient required Total NPK (t ha-1) N P K (kg ha-1)
80 146 56 170 372
90 165 63 191 419
100 183 70 212 465
110 201 77 233 511
120 210 84 254 548
130 239 91 275 604
140 256 98 296 650
150 275 105 317 697
160 293 112 339 744
170 311 119 360 790
180 329 126 382 837
190 348 133 403 884
200 366 140 424 930
Source: Naidu, 1999.
11 .5
SULPHUR
Intensive agriculture and use of sulphur free complex fertilizers have caused widespread deficiency. Hence it assumes great importance in sugarcane nutrition and is next only to NPK. The typical deficiency symptoms are: intervenial chlorosis, leaves become narrower, shorter and pointed. Canes are thinner and taper rapidly at the tips (Tandon, 1991).
Sulphur in soil exists as organic S, soil solution S and is adsorbed on clays and oxides of Fe and Al (Allophanes). The immediate source of S to crops is SO4 in soil solution. This is replenished by desorption from soil clays and hydrous oxides. It is reasonable to assume that SO4 adsorption is beneficial since it prevents or minimises leaching losses.
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Sugarcane in agriculture and industry
Mineralisation of sulphur is associated with C : S ratio of 200 : 1 or N : S ratio
of 10 : 1 to 20 : 1. But immobilisation takes place at a C : S ratio of 400 : 1.
Normally rains add 10 kg ha -1 S. Due to atmospheric pollution, S compounds are
in gaseous or in particulate or aerosol form.
Sulphur requirement ofcane is about 0.91 kg per ton of millable cane or 1.81 kg
per ton of dry mater. Tandon (1991) observed that a crop of 87 t ha -1 removed
2 to 4 kg S ha - 1 which approximates to 0.3 kg per ton of millable cane. Also it is
observed that uptake of S by sugarcane mirrors dry matter production.
170
Fig 1 1 . 1 1 Effect of sulphur on cane and sugar yield (Gosh et al. 1990)
In a more systematic study, Fox (1976) has found internal (40 kg S ha -1) and
external (10 kg S ha -1) S requirement for cane. Improved cane yield following S
addition is reported by several workers (Fox, 1976, Ghosh et al., 1990). In an S-
deficient alluvial soil at Lucknow in Uttar Pradesh, significant yield increase was
recorded following S application and 80 kg S ha - 1 seems optimum (Fig. 11.11)
Yield increase of about 10 t ha - 1 was attributable to more millable canes, heavier
canes and root weight. Tandon (1991) while reviewing Indian work reported yield
increase from 10 to 32 t ha -1 with a mean value of 21 t ha -1 due to sulphur
dressing. Under All India Coordinated Project, Yadav (1999) reported yield in
crease from 170 to 585 kg cane per kg S at 20 kg ha - 1 in the subtropics. In the
tropics, the response ranged from 130 to 250 kg cane per kg S. In Thiruvalla,
Kerala, response increased from 80 to 250 kg cane per kg S when the application
11 Nutrition and fertiliser management
rate increased from 20 to 80 kg S ha - 1 . Yadav (1999) asserts that besides NPK,
application of S is likely to be essential for increasing cane productivity. Recent
research reveals that S dosage may range from 40-80 kg ha -1 , depending on soil
type and management practice. Ghosh and his associates (1990) observed that S
was directly connected with N utilization and thus improved Nitrogen Use Effi
ciency (NUE). Better N U E following S application is possibly associated with
increase in nitrate reductase activity which is a key enzyme for the utilization of N
in the plant (Table 11.21).
According to Ghosh et al. (1990), a critical soil S is 40 ppm. However, this is at
variance with Tandon (1991) who indicated 20 ppm in ammonium acetate ex
traction (0.5 N N H 4 O A C + 0.25 N HOAC). Based on the available information,
it is generalized that the critical soil S is 20—30 ppm for sugarcane. But the critical
S concentration ranges from 0.5 to 0.8% in index leaf sheath, and in index blades
from 0.08 to 0.15% (Jones, 1985).
Table 1 1 . 2 1 Effect of S on N use efficiency (NUE) and in vivo nitrate reductase
activity (dm (g) g-1 N m - 2 )
Levels of S N U E Nitrate reductase activity
ppm (dm (g) g-1 N m - 2) (n mol NO2 g -1 fresh wt. hr -1
0 2.166 1652.4
40 2.226 1774.8
80 3.015 1989.0
120 2.536 2020.3
160 2.667 1805.4
Source: Ghosh et al. 1990.
11.5.1 Sources of S
Ammonium sulphate, gypsum, single super phosphate, ammonium phosphate
sulphate, pyrites and industrial wastes like press mud are good sources of S. At a
given level of S, press mud is inferior to gypsum and single super phosphate, but
superior to pyrites. Yaduvamshi and Yadav (1991) showed that sulphitation press
mud is a more effective source of S for sugarcane as it contains 2 - 3 % S. Wherever
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Sugarcane in agriculture and industry
S deficiency is encountered, 50-100 kg elemental sulphur per ha may be mixed in the soil prior to planting. Large increases due to soil application of elemental S have been reported from alkaline-calcareous soils of Rajasthan.
In such soil, the effect of sulphur effect is partly due to lowering of soil pH and correcting of crop chlorosis.
11.6
CALCIUM AND MAGNESIUM
For near normal growth of sugarcane, 12% Ca saturation of exchange complex is
suggested (Tisdale et al. 1985). A crop yielding 88 t ha - 1 is estimated to remove
132 kg Ca ha - 1 (Hunsigi, 1993b). The critical level of exchangeable Ca in soil is
around 100 ppm. The Ca index (3-6 leaf sheaths) is 0.14 to 0.175% or 0.06% in
8-10 internodes. Top Visible Dewlap Lamina (TVD) is perhaps more sensitive to
Ca deficiency for which threshold values are 0.05 to 0 . 1 % Ca.
Acid soils in India cover about 50 m ha and occur in the Eastern, North East
ern and Peninsular regions (Biswas et al. 1985). These soils are deficient in Ca and
Mg. Sugarcane grown in acid soils of Kerala, Assam, West Bengal and Goa re
sponds to liming. Application of limestone at 1-3 t ha - 1 is recommended to plant
crop, which takes care of subsequent ratoons also.
Magnesium is more mobile in the plant than Ca. A ton of cane removes 0.85 kg
Mg (Clements, 1980). Mg shortage is accompanied by thinner stalks, shortened
internodes and internal browning (Evans, 1959). The T V D leaf of affected plant
contains 0.03 to 0 .5% Mg. Threshold exchangeable Mg in soils is around
30—50 ppm but sheath Mg of 0 .1% or 0.05% in 8-10 internodes appears to be
adequate. Clements (1980) suggests a tentative optimum level of Mg at 0.175%
in 3-6 leaf sheaths. Field deficiency of Mg by sugarcane grown in India has not
been observed. But in acid soils, it is safe to thoroughly mix dolomite in soil at
500 kg ha - 1 which provides both Ca and Mg. However, Biswas (1991) observed
that many soils in South China are deficient in Mg. Sugar and starch crops have
high Mg requirement. The sugarcane yield jumped from about 53 t ha - 1 in NPK
treated plots to 103 t ha - 1 by application of NPK + Mg. He recommended broad
casting 0.5 — 1.0 t ha - 1 of dolomite to these soils.
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11 Nutrition and fertiliser management
1 1 . 7
SILICON
Paddy and sugarcane are high siliciferous plants and the importance of Si has been recognised since the time of Liebig. Saccharum sp. and the allied genera are known accumulators of silicon. Its essentiality is questioned. However, the consensus is that it is a beneficial element (Wild, 1988). The beneficial effect of Si is due to its structural role, it increases resistance to insect pests and reduces lodging. It increases strength and rigidity of cell walls and is instrumental for better water relation. Silicon application to soil raises soil pH, reduces P fixation and toxicity of Fe, Al, Mn, Zn and other metallic ions.
The control of 'freckling' in sugarcane is due to Si application, which acts as a corrective measure to excess absorption of Fe, Al, Mn, Zn etc. (Clements, 1980). Further, decreased acidity following Si addition caused better microbial activity and release of organically bound N, P, and S. Better water use efficiency is also attributed to Si uptake. In a significant contribution, Alexander (1973) contended that Si application (in a narrow concentration) inhibits invertase activity and lowers the levels of acid phosphatase, improving sucrose synthesis. Clements (1980) has presented the critical limits for secondary and beneficial elements in elongating leaf sheaths.
Dry weight, soluble sugar-free basis, % in 3—6 leaf sheaths
Ca Mg S Si
0.17 0.08 0.22 2.2
Source: Clements, 1980.
Response of cane to silicate materials can be anticipated only in highly water
logged tropical soils with low pH. This author admits that there is no significant
response to soil application of silicate amendment in acid soils of Kerala, Assam,
and West Bengal. But quality distinctly improves following the silicate sprays.
Calcium or sodium metasilicate acts as a ripener by converting reducing sugars in
the top internodes to recoverable sugars.
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Sugarcane in agriculture and industry
1 1 . 8
MICROINUTRIENTS
Micronutrients or trace elements are required in small quantities, yet play a pivotal role by participating in the enzyme systems. These invariably have synergistic or antagonistic effects with other nutrients. They interact with secondary elements such as Ca, Mg, Si and S, and have large influence on yield and quality of cane. Another secondary element Na is beneficial to sugarbeet but is distinctly harmful to sugarcane for it reduces cane quality. However, with inadequate K supply, Na in a narrow range can take the physiological function of K. The importance of Na and C1 for C4 plants, notwithstanding sugarcane, was well recognised for they increase the activity of phosphoenolpyruvate carboxylase, a primary enzyme in photosynthesis (Tisdale et al., 1990), of C4 plants. Interestingly, lack of Na will cause some plants to shift their CO2 fixation pathway from C4 to C3 (op. cit.). Both Na and C1 are known to regulate water relation and largely influence sugar output.
Under field conditions the deficiencies of Mo, C1, Cu and B are practically unknown (Jones, 1985). But deficiency of Fe, Mn and Zn is of economic importance for sugarcane grown under field conditions.
Based on the available literature, some generalizations are presented in Table 11.22 with regard to the role of minor elements in cane yield and sugar output. Further, the FUE of micronutrients is very low, in the range of 2 - 3 % (Singh, 1999).
Investigation in sand culture showed that the deficiency of Zn, Cu, and Mo causes chlorosis and shortening of internodes and depression in catalase activity (Agarwala et al., 1986, 1987). While maximum reduction in catalase activity was observed in Mo deficient plants; boron deficiency caused marked reduction in sucrose in cane stalks. The critical limits in elongating leaf sheaths of sugarcane reported by Clements (1980) are 2 ppm B and 10 ppm for Zn, Cu, or Mn on sugar-free dry weight basis.
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11 Nutrition and fertiliser management
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Sugarcane in agriculture and industry
11.8.1 Iron and manganese
Iron deficiency cannot be seen in isolation since iron interacts with Mn. True iron
deficiency is quite rare since sett contains sufficient Fe to support early growth.
But lime, carbonate, bicarbonate, P, and heavy metal induced iron chlorosis is of
frequent occurrence in States of Punjab, Uttar Pradesh, Bihar, West Bengal, Ma
harashtra, and in certain areas of Tamil Nadu and Karnataka. Iron-manganese
interactions-are well documented. In normal cane Fe : Mn ratio is 15 : 1 or more.
But Fe deficiency/Mn toxicity results in a narrow ratio of 1 : 1 or even less. Iron
deficient plants accumulate Fe in the nodal region. It is reasonable to assume that
inactivity of Fe in the tissues due to high pH of cell sap is responsible for iron
chlorosis. Further explanation is given by Marschener (1998) who states that in
calcareous soils p lants adopt "strategy I I " wi th e n h a n c e d release of
phytosiderophores (PS) with specific uptake system for Fe+3.
Amelioration of Fe deficiency is achieved by soil application of FeSO 4 at
25-30 kg ha -1 or foliar spray of 2%. Yadav (1993) obtained a field response of
2083 kg and 2508 to 7809 kg cane per kg of soil applied Fe and Mn respectively.
He recommended 10 kg ha -1 of soil application of MnSO 4 in Mn deficient soils.
As foliar spray the response was 5800 kg ad 2340 kg cane per kg of FeSO 4 and
MnSO 4 respectively (loc. cit.) Iron chelates like Fe EDTA or Fe E D D H A are
more effective than iron salts. However, sulphur application at 500 kg ha - 1 is
most effective in correcting the iron chlorosis.
It can be concluded that S application created balanced nutritional environ
ment, forestalled chemical/biological inactivation of Fe and thereby improved
yield and quality of cane.
Manganese differs from other elements in that both deficiency and toxicity can
be seen under field conditions. Interveinal chlorosis is a distinct symptom of Mn
deficiency in sugarcane. In Mn deficient soil 10 kg MnSO 4 ha - 1 is applied to soil.
Foliar application at 2 kg ha - 1 as MnSO 4 is equally effective.
11.8.2 Zinc
The deficiency of this element in sugarcane is widespread and is frequently en
countered when sugarcane is taken in rotation with rice. In South Africa large
areas show Zn deficiencies due to monocropping (Meyer, 1999). The deficiency
symptoms can be recognised by the stunted growth and patchy appearance. The
176
11 Nutrition and fertiliser management
distinctive symptoms are: defective and deteriorative spindle, young leaves tend to curl and stalks are severely piped. Severe Zn deficiency often results in drastic reduction in cane and sugar yield. Liming induces Zn deficiency and solubility decreases as pH increases. Antagonism between Zn and P is well documented; they are physiologically inactivated in the roots itself. This adversely affects the translocation of both the elements to the upper plant parts. Besides P, high concentration of Fe, Mn, and Cu causes severe Zn deficiency. This can, however, be overcome by soil application at 20-25 kg Z n S 0 4 ha - 1 or foliar spray of 1-2%. Yadav (1993) obtained a response of 2181 kg cane per kg of Zn applied through soil. The response to foliar spray was 5518 kg per kg Zn. It is evident that foliar spray is superior to soil application. Among the varieties, Co 6304 responded more in tonnage to application of Zn and other micronutrients than CoC 671 and CoC 8201. Interestingly in Sindh province of Pakistan, sugarcane setts are treated with zinc oxide (0.2%).
11.8.3 Other micronutr ients
Under field conditions the deficiency of Mo, CI, Cu, and B in C4 plants is prac
tically unknown (Jones, 1985). It is observed that the level of C1 in sugarcane is
high enough to be recognised as a major element. Agarwala and his associates
(1987) in sand culture studies observed maximum reduction in catalase activity
in Mo deficient plants. The problems of Cu and Mo is less severe than Fe since the
former elements have residual values. Boron deficiency results in marked reduc
tion of sucrose in cane stalks. The primary role of B is the transport of sugars
across cell membranes as poly-hydroxyl-complexes (sugar-borate complexes). This
author obtained more than 1% pol in juice following a boron spray (1 kg B ha - 1) .
Copper exists in the chemisorbed or occluded form in hydrous oxides of Fe,
Al, Mn or complexed with organic matter. This explains its low availability in
histisols of Florida (Barnes, 1974). The copper deficiency in cane is well recog
nised by 'droopy top' and slow unfurling of spindle leaves. The stalks are soft and
rubbery in Cu deficient plants. There is hardly any need to apply Cu through soil/
foliar for sugarcane grown in vertisols/alfisols/entisols of tropical or subtropical
India.
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Sugarcane in agriculture and industry
11.9
VISUAL SYMPTOMS OF NUTRIENT DEFICIENCIES AND DISORDERS
Nutrient deficiencies and their disorders can be recognised by visual symptoms
which are very characteristic to that nutrient. This needs a very close observation.
And a lot of experience is needed to diagnose them visually and suggest remedial
measures. The typical deficiency symptoms in sugarcane are listed here under.
Nutrient Mobility in plants Symptoms
N
K
Ca
Mg
Zn
Fe
Highly mobile
Highly mobile
Highly mobile
Immobile
Slightly mobile
Highly mobile
Mobile
Immobile
Paling or chlorosis of old leaves reduced tillering,
gradually entire crop appears yellowish and growth
stunted.
Stunted growth, purple, orange or pink colour of
leaves, prominently seen in young leaves in wee
hours. Older leaves dark green colour. Reduced
tillering and lowered shoot root formation.
Older leaves show marginal burning starting from
tips. Inverted 'V Shaped burning ('marginal fir
ing'). In extreme case the entire plot looks 'fired'
(brown coloured).
Rarely encountered under field conditions. New
leaves become white, growing points die and curl.
Marginal or interveinal cholorosis with pinkish
colour of older leaves. Some times leaf rolling
occurs as in drought conditions.
Interveinal chlorosis of older leaves, leaves become
narrower, shorter and pointed. Canes Thinner and
taper at the tips.
Stunted and patchy growth. Rusting in 'strips'
of older leaves, chlorosis in mature leaves
reduced tillering.
Chlorosis of younger leaves. Under severe defi-
ciency entire leaf becomes yellow and then white.
con td.
178
s
179
11 Nutrition and fertiliser management
contd.
Nutrient Mobility in plants Symptoms
Mn Mobile Interveinal chlorosis, starts from older leaves.
Advanced stages show necrosis.
Cu Mobile Rare under field conditions. Young leaves become yellow, stunted. On severely affected older leaves die back. Advanced stages dead tissue appears along tips and edges of leaves, similar to K deficiency.
Cl Highly mobile Very rare under field conditions. Chlorosis of
young leaves, rolling and die back.
Mo Mobile Mottled pale appearance in young leaves bleach
ing and withering of leaves. Bo Mobile Pale green tips of blades, bronze, tint, death of
growing point.
Table 1 1 . 2 3 Critical nutrient concentration in index tissues.
Sugarcane in agriculture and industry
The critical or threshold nutrient concentration in index tissues at early to
grand growth stage (3-6 months) are presented in Table 11.23.
11.10
NUTRITION MANAGEMENT
11.10.1 Soil and t issue test ing
Soil testing remains an excellent pre-plant advisory tool although soil-test crop
correlations are still to be worked out in many cases. As a very general indication,
soils having less than 0.5% organic carbon or 250 kg ha - 1 of alkaline permanga-
nate-oxidisable N are rated low in N, soils having less than 20 kg P 2 0 5 ha-1 are
rated deficient in P, and those having less than 150 kg K2O ha -1 are rated low in
available K.
Tissue tests quantify the nutrient status of the plant, and can be supplemented
with soil test data.
11.10.2 Crop logging
Clements (1980) is credited with having given a comprehensive system, popu
larly known as 'crop logging'. According to him, the crop log like a ship's log is
record of progress from its start until the arrival of harvest. It is essentially a criti
cal concentration approach and critical levels need to be determined for each
region.
By and large, sheath moisture index (3-6 leaf sheaths) is universally accepted as
a single parameter which predicts the performance of the plant. Another advan
tage of crop log data is that midterm corrections can be made. The index tissue of
N is 3—6 leaves and for all other elements 3—6 leaf sheaths are taken. Work done in
India shows that crop logging based on index sheaths is better than stalk logging
(8-10 intemodes) or third dewlap (Lakshmikantham et al., 1970). The indices
supposed to give good growth, high yield and better sugar recovery in tropical
and subtropical regions of India are given in Table 11.24. It is intriguing that crop
log is rarely adopted in sugar factories in India.
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11 Nutrition and fertiliser management
Table 1 1 . 2 4 Crop log data for different growth phases of sugarcane in South India
11.10.3 Diagnosis and Recommendations Integrated System (DRIS)
The critical or threshold concentration (crop log) approach has been contested as
a means to fertilise the crop. Hence DRIS has been suggested as a better alterna
tive. It provides a method of simultaneously identifying imbalances, deficiencies
and excesses in crop nutrients and ranking them in order of importance
(Bailey et al., 1997). The DRIS model is designed to show when the nutrient
contents of crops are insufficient (—ve indices), adequate (zero indices) or exces
sive (+ve indices) for maximum dry matter production. In essence, DRIS takes
into account nutrient ratios. Apart from nutrient ratios, dry matter index has also
been developed. The Nutrient Balance Index (NBI) denotes the balance among
nutrients and is obtained by adding the values of DRIS indices irrespective of
their sign. The larger the value of NBI, greater is the imbalance among nutrients.
The chief advantage of DRIS over crop log lies in its sensitivity to factors like type
and age of tissue, position of the tissue or the cultivar. A typical DRIS chart
showing NPK requirement by sugarcane (Cv Bo varieties) grown in aridisols
(calciorthids) is shown in Fig. 11.12. The DRIS chart shows the zone of suffi
ciency and nutrient imbalance. The DRIS is not employed in India as an advisory
tool for scheduling fertilizer application to sugarcane. It has been found useful in
South Africa and USA, for the large plantations there.
181
Sugarcane in agriculture and industry
The South African sugar industry greatly depends on soil and leaf analysis
conducted by its Fertilizer Advisory Service (FAS) for identifying and correcting
nutrient disorders in sugarcane (Meyer, 1999). The computerisation of FAS rec
ommendations lead to a programme known as NIRS (Nutrient Information Re
trieval System). NIRS stores soil and leaf analysis data to categorise soils with
respect to their nutrient deficiency or sufficiency levels. Yield plateauing of sugar
cane is attributed to acidification, Al-toxicity and P-fixation (op. cit.).
Fig 1 1 . 1 2 DRIS chart showing N, P and K requirement by sugarcane—A case
study with BO varieties
11.10.4 Integrated Nutrient Management System (INMS)
High input agriculture is at the crossroads and environmentalists warn us of seri
ous ecological imbalance nothing short of disaster. Therefore, emphasis is now
placed integrative processes such as minimum/conservation tillage, use of cover
crops, green manuring and residue management to avoid crusting and compac
tion. Recycling of industrial or organic wastes improves water and fertilizer use
efficiency. Moreover, the nutrient ratios (N : P2O5 : K2O) have been very wide for
182
11 Nutrition and fertiliser management
sugarcane (12 : 3 : 1). The optimum ratio for sugarcane is 2 : 1 : 2 (Humbert,
1968). A rational blend of organics and inorganics will remove the constraints,
contain yield plateaus and help to maintain soil quality. Sustained production of
cane and sugar is possible through INMS and its components as follows:
(a) use of organics such as farmyard manure, compost, etc.
(b) green manuring
(c) rotation and /or intercropping with short duration leguminous crops
(d) crop residues (stubble, trash etc.) incorporation
(e) use of industrial wastes
(f) biofertilizers—N2 fixers both symbiotic and associative and P solubilizers
(g) balanced and optimal dose of inorganic fertilizers including the use of sec
ondary nutrients and micronutrients (whenever needed).
Integration implies a happy blend of organic and inorganic sources of fertilis
ers and bioagents. It is reasonable to postulate that at least 30% of chemical ferti
lizers should be replaced by organic sources and biofertilizer. Yadav (1999) has
presented a big jump in cane yield following INMS (Table 11.25) in different
locations.
Table 11.25 Effect of integrated use of Sulphitation Press Mud Cake (SPMC) and biofertilizers with fertilizer nitrogen on yield of sugarcane planted crop at different locations
183
Sugarcane in agriculture and industry
T a b l e 1 1 . 2 6 Constraints in fertiliser use and suggested remedial measures in
important cane erowine areas of the country
Productivity (t ha - i) State Present Immediate Constraints in Remedial measures/
1995 achievable fertiliser use strategies
-1996
Andhra 71.1 84.5 a) Moisture stress Supplemental irrigation Pradesh and late K dressing
b) Waterlogging Drainage
in some areas
Assam 43.0 50.0 a) No proper fertilizer Balanced fertiliser use
schedule
b) Soil acidity Liming at 1-3 t ha - 1
Low-yielding varieties Responsive varieties
Bihar 53.7 60.0 a) No proper dose, Balanced fertiliser
time and method use of NPK 2 : 1 : 2
of application Adequate early N
fertilisation & PK dressing
b) Waterlogging Drainage
c) Poor ratooning Ratoons to be manured
Karnataka 80.5 85.0 a) Imbalanced use Balanced use of NPK
of fertilisers i.e. 2 : 1 : 2
b) Improper time and Point placement of
method of application fertilisers at peak need
c) Heavy dose of N
in canal areas
d) No proper varietal mix
Kerala 66.1 70.0 a) Fertiliser responsive Responsive varieties
variety needed to be identified
b) Soil acidity Use of liming material
including filter cake
c) Moisture stress at Trash mulching
grand growth
contd.
184
11 Nutrit ion and fertiliser management
Table 11.26 contd.
Maha- 88.8 104.7 a) Moisture stress Supplemental irrigation rashtra in non-canal areas from groundwater,
Trash mulching b) Saline alkali Reclamation through
filter cake application
Punjab 63.1 75.0 a) Freezing temperatures Use of polythene mulch or
and low FUE trash mulch to warm soil
soil to improve FUE
b) Saline and alkali soils Reclamation by amendment
Tamil 101.2 110.0 a) Moisture stress Trash mulching and late
Nadu K dressing
Exploitation of groundwater
Uttar 55.3 81.6 a) Low fertiliser dose Opt imum fertiliser use for
Pradesh and ratoons taken plant and ratoon crops
as free crop
b) Faulty method and Band placement at peak need
time of application
c) Moisture stress Trash mulching
Source: Srivastava et al. 1988 (modified). FUE = Fertiliser Use Efficiency
11.10.5 Constraint analysis
The production potential of cane is 475 t ha - 1 . Some progressive farmers in Ma
harashtra and Karnataka have attained yields of over 250 t ha -1 . This big yield gap
can be bridged by better management of fertilizers, water and adoption of supe
rior management practices. Some of the constraints in fertilizer use and their
remedies in major cane growing areas of India are listed in Table 11.26.
185
Productivity (t ha -1)
State Present Immediate Constraints in Remedial measures/
1995 achievable fertiliser use strategies
-1996
Sugarcane in agriculture and industry
In the final analysis, fertiliser management holds the key for economic produc
tion of cane. The integrated nutrient supply system comprising organic and inor
ganic sources, biofertilisers and green manuring ensures sustained cane and sugar
production. Spot application of fertilisers and synchrony between nutrient de
mand by plants and supply help to improve substantially the fertilizer use effi
ciency.
1 1 . 1 1
BIOLOGICAL SOFTWARE IN SUGAR INDUSTRY
The Biological Software (BSW), naively defined, are the microflora and fauna
which increase nutrient bioavailability, enhance degradation of crop residues, in
crease pathogenesis and offer resistance to many biotic and abiotic stresses. The
general BSWs are show in the flow diagram.
The rhizosphere, the volume of soil influenced by root activity, supports ben
eficial bioagents like N2 fixers, plant growth promoting rhizobacteria, and phos
phate solubilising bacteria. There is rhizo disposition and lowered pH due to the
production of organic acids. Phytosiderophores or root exudates are produced
with strong complexation of metal ions. Root exudates detoxify Pb, C D , Al, etc.
due to complexation. There is production of Plant Growth Regulating substances
(PGR) or growth hormones (Hyperauxiny) like IAA, IBA, gibberellins, cytokinins,
and ethylene. Change in redox potential increases Fe+2 (ous) ionic species with
enhanced Fe availability, with reduced iron chlorosis. Rhizosphere is implicated
in pathogenesis (pathogen attraction). The poor root syndrome of sugarcane caused
by Pythium graminicola may possibly be controlled by rhizobacteria. In essence,
all nutrients are acquired, sense strictu from the rhizosphere.
Of concern to sugarcane are associative N2 fixers (Rhizocoenosis). In tropical
soils, N is the most deficient nutrient element. Hence Biological Nitrogen Fixa
tion (BNF) has an assured place in agriculture. The free living organisms (non-
symbiotic) found in association with sugarcane are Azotobacter sp., Azospirillum
sp., Acetobacter diazotrophicus, Bacillus, etc. Azospirillum is associative and
microerophylic and performs well under low O2 tension; hence it is preferred in
compacted ratoon soils. Azotobacter is aerobic, hence, it is suited to planted crop.
Azotobacter fixes 30-35 kg N ha - 1 . Azospirillum is an important bacterial group as
it secretes PGRs like IAA and GA. It has high adaptability to varied temperature
186
11 Nutrition and fertiliser management
and soil p H . Acetobacter diazotrophicus, a saccharophilic bacterium is known to
significantly enhance sugarcane yields.
Cellulolytic microbes such as Cellulomonas, Trichoderma viridae decompose
recalcitrant material like trash and hasten production of humus. Further sapro
phytic fungi of Trichoderma are antagonistic to pathogenic fungi. 77 viridae and
Paecilomyces lilacinus have the most potential as bio-control agents for soil borne
pathogens, i.e., root rot, wilt, damping off, etc. Incidentally, it is worthy of note
that T. harzianum has allelopathic effect on successive ratoons of cane.
Generally, cellulolysis and diazotrophy are carried out by a mixed microbial
community (microbial consortium) in which N2 fixers can use either cellulose
and/or hemicellulose directly or their byproducts.
Mandal and Sen (1999) reported that siderophores produced by Aspergillus
niger AN 27 have fungistatic activity with better Fe supply to plants. They con
firm that A. niger AN 27 produced bo th groups of siderophores, namely,
hydroxamate and catecholate. Thus A. niger AN 27 has antagonistic activities,
rhizosphere competence and promotes growth.
Phosphate solubilizing microbes were causal in enhancing P and K uptake
with improved yield and quality of cane. This includes fungi, such as Aspergillus
awamori, Pencillium digitatum, and bacteria like Bacillus polymixa and Pseudomonas
187
Sugarcane In agriculture and industry
straita. Soil inoculation of Agrobacterium radiobacter or Bacillus magatherium in
plant crop and Aspergillus awamon or Bacillus megatherium in ratoon crop im
proved yield and quality with 25% saving in P fertilizer.
' Mycorrhizae (ecto and end-) involves a unique symbiotic associate n between
plant roots and injecting fungi. The hyphae of Vesicular Arbuscular Mycorrhizae
(VAM) are the extension of the root system and are in fact P-mobilizers. This
association has increased nutrient uptake resistance to drought, salinity and. in-
leased tolerance to pathogens and promoted better soil aggregation. Sugarcane
has shown variable response to VAM (Glomus sp., Gigaspora, Acaulospore,
Solerorystis,). The VAM is more effective in P-deficient soils. These also improve
seedling vigour and growth. VAM has a role in the nutrition of P, Zn, Cu and S.
The importance of earthworms (Lumbricidae) has been known since the Ro
man times. These are aptly called the Cinderella of organic matter. The impor
tance of burrowing activity in relation to drainage, aeration, and soil aggregation
is well recognised. The mixed population of Eudriulus eugcniae, Perionyx excavatus
and Eisenia fetida in partially decomposed waste ensures a good vermicompost
which is a friable, loose humus with excellent manurial quality.
188
Water management
Sugarcane tolerates moisture stress to some extent but responds to irrigation; sub
stantial inputs of water are needed to achieve maximum yield. Yields have been
found to increase directly with the amount of water available for unirrigated plots,
irrigated furrows and drip irrigated crops and upto a water application rate
1.46 times the rate of pan evaporation (Wiedenfeld, 1995). In tropical India the
number of irrigations range from 30-36 while in the subtropics it is 5-10. The
duty of water for sugarcane is fixed at about 80 ha or 200 acres. The water require
ment of sugarcane grown in India varies widely from 114.3—304.8 cm
(Hapase et al.3 1990). In Maharashtra where the annual rainfall is about 50 cm,
the water requirement of sugarcane varied from 240 to 300 cm for suru crop
(January—February planting) and 320 to 350 cm for adsali crop (June—July plant
ing). The water requirement of sugarcane grown in different states is given below.
Besides climatic and soil factors, the large variation in water requirement is due
to variation in the duration of the crop, ranging from 12 to 18 months. In a
recent study, Gupta and Tripathi (1998) stated that the water requirement in the
subtropics ranges from 800 to 1200 mm in the subtropics and from 1500 to
2000 mm in die tropics.
Soil also influences water requirement as it determines water holding capacity
(Sundara, 1998). The water availability increases with the fineness in soil texture.
In general, the available soil water (—0.033 to - 1 . 5 Mpa) in heavy textured soils is
200 mm, in medium textured soil is 140 mm and in coarse textured soil is 60 mm
per metre depth of soil. Quoting others, Sundara (1998) has presented available
soil moisture holding capacity of different soils in India (Table 12.1).
There are some special features of water requirement in sugarcane. There is a
linear relationship between water use and dry matter production. A positive N x
irrigation interaction is prominent which suggests that if the water supply is lim-
189
Sugarcane in agriculture and industry
ited, sugarcane cannot take advantage of increased N availability (Wiedenfeld,
1995). However, mild water stress is necessary to promote root growth. Excessive
water at tillering reduces tiller production. A clear 'cut-out' or 'dry-off period of
4-6 weeks prior to harvest ensures better sugar recovery. According to Robertson
and Donaldson (1998) abstraction of water for 6—8 weeks during the maturation
phase is beneficial. But they caution that increase in sucrose yield occurred when
decrease in stalk biomass was no greater than 10%. This is the basis for determin
ing the trade-off between the reduction in stalk biomass and sucrose yield. Admit
tedly, increase in sucrose concentration occurred due to increase in soluble solids
and dehydration.
Table 12 .1 Approximate available soil moisture holding capacity of different
soil textural classes
12.1
EVAPOTRANSPIRATION (ET) OR CONSUMPTIVE USE (CU), IRRIGATION EFFICIENCY (IE), AND WATER USE EFFICIENCY (WUE)
The terms Evapotranspiration (ET) or Consumptive Use (CU) are used to desig
nate the losses due to evapotranspiration and the water that is used by the plant
for metabolic activities since the water used in the metabolic process is insignifi-
190
12 Water management
cant (1.0% of ET). ET for sugarcane has been calculated by Hunsigi (1993a) based on the modified Penman's equation.
ET = Kc. ETm ,
where ET m is maximum ET with no limitation of water and K is the crop coefficient.
For sugarcane, K is a minimum of 0.5 at crop emergence, has a maximum
value of 1.15 at full canopy and declines to 0.6 at maturity. ET or CU can be
calculated from USWB Pan evaporation (EO) since a good correlation exists be
tween ET and E O . The coefficients for sugarcane range from 0.4 at the juvenile
stage to 0.8 at the formative stage. The peak water need is at the 'rapid close-in
period' or boom phase and the coefficient could be 1.0 to 1.2 (Fig. 12.1). Robertson
and Donaldson (1998) suggested a factor of 1.46 at the grand growth phase.
Figure 12.1 is suggestive that the coefficient declines to 0.6 at maturity.
Fig. 1 2 . 1 ET as a function of crop factor (F) and pan evaporation (Eo)
(ET = F.Eo)
The Irrigation Efficiency(IE) indicates how efficiently the available water sup
ply is used (Michael, 1978). The degree of land preparation, the irrigation system,
and the skill and care of the irrigator are the principal factors influencing irriga
tion efficiency. Loss of irrigation water occurs in conveyance and distribution. In
sugarcane, mostly ridges and furrows are made and the runoff losses are highest at
the end of the irrigation borders and furrows. The Irrigation Use Efficiency (IUE)
is defined as the ratio of cane yield to the total amount of irrigation water used.
191
Sugarcane in agriculture and industry
The important parameter most often used is Water Use Efficiency (WUE)
which is defined as the ratio of cane yield to seasonal net water used. In the present
context, WUE is defined as the ratio of cane yield and consumptive use.
WUE = Y/ET
Soopramanian (1999) in his review has shown that WUE ranges from 30 to 20 t ha-1 per 100 mm of water. The WUE for different countries may be obtained from the slope of the relationship between cane yield and water use. Hunsigi (1993a) has shown that WUE ranges from 0.7 to 1.45 t ha -1 cm -1 in different sugarcane growing regions of the world. He concluded that WUE of 1.0 t cane ha-1 cm -1 or 0.11 sugar ha-1 cm-1 is optimum under the furrow irrigation system. Gupta and Tripathi (1998) have shown that WUE varies from over 400 to 2200 kg cane ha-3 cm -1 in different agro-climatic conditions of India (Table 12.2).
Table 12 .2 Water Use Efficiency (WUE) of sugarcane grown in different agro-
climatic regions of India
WUE can be increased by improved varieties, N application, and irrigation method. To further improve WUE, farmers in Australia are introducing ring tanks or dams to collect tail water and surface runoff during the rains (Soopramanian, 1999). This water is recycled.
Adequate soil moisture is necessary for growth, development, and yield of cane.
This also influences sucrose content and ultimate sugar recovery. Periodic soil
192
12.2
SOIL MOISTURE STATUS AND LEAF WATER POTENTIAL
12 Water management
samples are taken to know the moisture status. It is highly tedious. Tensiometers
are installed at regular intervals and irrigation is resumed when the tensiometer
readings are —25 to —35 Kpa.
In Australia and Columbia, mini-evaporation tanks are used to schedule irriga
tion. It is a device with a plastic bucket of 20 litres capacity. T h e minimum stor
age capacity is defined by the height of the overflow orifice near the rim and two
marks indicate the need to irrigate when the water level approaches them
(Soopramanian, 1999).
Turner (1990) pointed out that plants mirror the water need better than the
soil does. For example, the sheath moisture index of 3-6 leaves is 8 3 - 8 5 % during
the active growth phase (tillering to grand growth) and is 72—74% at maturity.
Similarly, 5 and 6 internodes (stalk logging) reflect the soil moisture status.
The leaf rolling index is a sensitive indicator of reduced soil-water availability.
But Inman-Bamber and Dejager (1986) reiterated that the leaf water potential
(ΨL) in situ is the most practical method of scheduling irrigation. The sequence of
events is presented in Table 12.3.
T a b l e 1 2 . 3 Leaf water potential (ΨL) of potted cane at different physiological
stages and moisture levels
Events Plant status ΨL (Mpa)
1. Plant extension rate reduced and the
youngest unfurled leaf begins to roll -0.8
2. Stomatal resistance starts to rise -0.8 t o - 1 . 0
3. Green leaf area reduced -1.0 t o - 1 . 7
4. Plant extension rate ceases and stomatal
conductance reaches a minimum -1.3 to —1.7
5. Youngest unfurled leaf becomes fully rolled -2.0
6. Least number of living leaves and eventual stalk death -2.8
Source: Inman-Bamber and Dejager, 1986.
It is concluded that irrigation should be resumed before the young leaves start
to roll at a leaf water potential (ΨL) o f-1 .0 to -1.5 Mpa.
Three cardinal questions that require an answer are:
193
Sugarcane in agriculture and industry
(a) When to irrigate? (b) How much to irrigate?
(c) How to irrigate?
12.3
WHEN TO IRRIGATE?
Table 1 2 . 4 Irrigation intervals for different textured soils under different
climatic regimes
Soil textural class Irrigation interval (days) Rabi Summer
Medium to fine textured deep soils 25-30 14-18
Coarse textured medium deep soils 10-14 5-6
Source: Deshmukh and Jadhav, 1999.
Table 12 .5 Irrigation intervals (days) for different cane growth phase under varying soil types
Growth phase Irrigation intervals (days)
Coarse Medium Fine
textured soil textured soil textured soil
Germination
(0-45 days) 5-6 6-7 8-10
Tillering
(45-120 days) 6-7 7-10 12-15
Grand growth
(120-270 days) 7 10 12-15
Ripening
(270-360 days) 10 12-15 15-20
A clear cut-out period is to be observed for 4-6 weeks prior to harvest
Source: Sundara, 1998.
194
12 Water management
Irrigation to the crop depends on the soil, the climate, and the physiological stage
of the crop. In sandy soils more frequent irrigations are given. Similarly in arid
climates and in the formative stage of the crop irrigation frequency is more. The
national seminar on irrigation suggested the following irrigation intervals
(Deshmukh and Jadhav, 1999) (Table 12.4).
Soils play an important role in scheduling irrigation, primarily due to their
available moisture status. Sundara (1998) has furnished irrigation intervals for
different growth phases of cane grown in varying soil types (Table 12.5).
The critical period of a crop is an important concept which aids in scheduling
irrigation. The critical period is the stage during which the absence of irrigation
results in yield reductions upto 50% or more. In sugarcane, tillering and grand
growth are critical stages. Even in tillering, the first, second, and third order tiller
ing are critical in that sequence. At the stalk elongation stage, abstraction of water
leads to shortened internodes with more pith formation. However, sugarcane can
recover from a short period of water stress when opt imum irrigation is resumed.
1 2 . 4
HOW MUCH TO IRRIGATE?
This also depends on the soil type. In sandy loam soils the normal depth of irriga
tion under furrow method of irrigation is 2.5 to 3.75 ha—cm at the early forma
tive phase. At grand growth including stalk elongation, the irrigation depth is 5.0
to 6.5 ha—cm. In Maharashtra, for cane grown under heavy soils the depth of
irrigation is 7.5 ha—cm. However, with increased depth of irrigation, irrigation is
less frequent.
Experiments have also demonstrated that sugarcane can be irrigated at 7 5 %
available soil moisture or 50% available soil moisture, if a trash blanket of
5-8 t ha - 1 is provided. This author has shown that irrigating cane at 74 mm
Cumulative Pan Evaporation or CPE (15 days interval), after providing a trash
mulch of 8 t ha - 1 , has resulted in a very high yield in sandy loam soils of Mandya.
Frequent irrigations at 19 mm CPE (4 days interval) and a trash mulch of
8 t ha - 1 greatly reduced the cane yield (Table 12.6). He has also observed that
irrigating cane at the rate of USWB Pan evaporation (1.0 x EO) was far superior
to irrigating at half the rate of pan evaporation (0.5 x EO) (Table 12.7).
195
196
12 Water management
Sugarcane in agriculture and industry
197
3™*r'T—^^"TT
Sugarcane in agriculture and industry
12.5
HOW TO IRRIGATE?
There are several methods to irrigate sugarcane. In subtropical India, wild flooding is practised where the cane is planted in flat beds. There is a considerable loss of water with reduced water use efficiency. The most common method of irrigation is the ridges and furrow method, which is essentially, a surface method of irrigation. There are micro-irrigation systems such as the overhead or sprinkler system and the drip system or trickle system.
12.5.1 Sprinkler irrigation
This is suitable in undulating topography and where surface irrigation is difficult. It simulates rainfall. The amount of water applied is equal to or less than the infiltration rate of the soil. Sprinkler irrigation is suitable in sandy soils where the infiltration rate is high. Hapase and co-workers (1990) at the Vasant Dada Sugar Institute, Pune have shown that the sprinkler system resulted in a yield increase of 15-20% with about 30 to 40% saving in water. In Cuba, over 50% of the cane area is irrigated through sprinkler systems.
Plastic pressure pipes or polyethylene pipes can be used with static or mobile machines. There is overhead equipment such as mobile gun travellers. The use of medium and low pressure nozzles (100 kPa or less) has helped to develop sprinklers such as drag line. They have gained popularity in African countries. The boom sprinkler system has been in use in some countries. The raingun sprinkler system can also be used to irrigate sugarcane fields. The centre pivot or linear move system is considered a recent breakthrough. The efficiency of the sprinkler system is as much as t ie drip system but the field corners are not irrigated. A software package HYDRUS-2D has been developed which allows analysis of water and nutrients (Soopramanian, 1999).
The sprinkler system has many disadvantages. It cannot be used in heavy clays, dark Mg clays and black cotton soils, where the infiltration rate is very low. It needs power and considerable skill to operate. It requires high initial investment; uniform water distribution is not possible on gusty-windy days. A serious problem of the sprinkler system is that the roots are shallow with a tendency to lodge.
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12 Water management
This system of irrigation is not found in India and the author is not aware of any
large-scale plantation under the sprinkler system of irrigation.
12.5.2 Furrow method of irrigation
This is the most common method of irrigating sugarcane in India. Despite poor
water application and low WUE, the furrow system is followed in large areas of
the world. Initially, ridges and furrows are made and cane is planted in the fur
rows. At final earthing up (3-4 months later), the ridge becomes a furrow and
serves as an irrigation channel. At this stage, long furrows are connected in the
form of a serpent; it is popularly known as 'serpentine method of furrow irriga
tion'. Fertilisers can be applied through the irrigation water (fertigation); a bag of
urea can be placed near the entry of water. The length of the furrow depends on
the slope and the soil type. In a level land, the furrow length could be 50-100 m.
Soopramanian (1999) has stated that if the furrow length is increased from
300 to 700 m, the W U E decreases from 7 3 % to 42%. Narrow 'V' shaped furrows
are preferred to wide 'U ' shaped furrows. Sundara (1998) has stated that in Tamil
Nadu 'check-basin cum furrow' irrigation is followed. In this, the water is let into
a set of 5-6 furrows which are connected at both ends. However, the check basin
method of irrigation is advocated in sodic soils.
The National Seminar on irrigation has recommended the replacement of the
traditional basin-cum-furrow irrigation by straight and contour furrows
(Deshmukh and Jadhav, 1998).
The straight furrows are suited where the land slope does not exceed 0.75%. In
intensive rainfall areas, the slope should not exceed 0 .5% to minimise soil erosion.
The contour furrow method is similar to the graded and level furrow methods
where furrows carry water across a sloping field rather than down the slope. Con
tour furrows are curved to fit the topography of the land. The furrows are given a
gentle slope along their length as in the case of graded furrows. Contour furrows
can be employed in most soil types except in light sandy soils or cracking soils.
Alternate furrow/skipped furrow irrigation
Under water scarcity situations, it is advisable to adopt skipped/alternate furrow
irrigation. The author has found that alternate furrow irrigation and skipped double
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Sugarcane in agriculture and industry
200
row planting economised the total water use by about 32%; the latter treatment
improved cane yield by 14% compared to the normal practice (Table 12.8).
Another low cost technology is to irrigate alternately—alternate irrigation. In
this system, the first furrow is irrigated and the second furrow is skipped. In the
next irrigation, the second furrow is irrigated and the first furrow is skipped and
so on. There is at least a 30% saving of water and this is suited to areas under well
irrigation and drought-prone areas.
Table 1 2 . 8 Effect of irrigation treatments on yield, yield attributes, quality
and total water used by plant cane
Treatments Spacing Plants Weight Cane Total Pol in
between per per yield water juice
rows m2 cane (t ha-1) used* (%)
(cm) (kg) (mm)
1. Alternate 90 15.72 1.00 110 1292 18.66
furrow
irrigation
2. Skipped 90 14.94 1.01 101 1193 17.03
furrow
irrigation
3. Double 60 16.72 1.05 129 1193 18.32
row planting
with 120 cm
skipped
4. Normal 90 16.50 1.25 113 1541 19.08
practice
(conventional)
*Inclusive of 455 mm rainfall.
Source: Hunsigi and Shankariah, 1982.
12 Water management
Surge irrigation
Surge irrigation is the regulated, pulsed application of water in furrows, irrigating
the permeable soils in furrows by interrupting the irrigation when only half or
two-thirds of the advance is completed (Stewart, 1995). The irrigation is then
completed 12—48 hr later. According to Stewart (1995), interrupting the supply
and dewatering of the soil decrease the soil infiltration capacity and thus improve
the water advance in subsequent pulses. It is believed that surge irrigation would
restrict deep percolation losses and permit uniform water application. The reason
offered for lowered percolation losses is the filling of the pores. The water saving
is 25—33% in sandy soils and 20% in loamy and clay soils.
12.5.3 Drip or trickle irrigation
Drip irrigation is the frequent and slow application of water to the base of the
root zone of each plant through mechanical devices or holes called emitters (drippers
or applicators) placed along the water delivery line. The drip system can be kept
on the ground surface, under the ground surface or even at a certain height above
the ground surface. The drip irrigation systems used in sugarcane can be catego
rised as follows:
I. Surface drip system
(a) Microtube system
(b) Pressure compensating drip system
(c) Non-pressure compensating drip system
II. Subsurface drip system
(a) Bi-wall system
(b) Turbo tape system
Studies at the Vasant Dada Sugar Institute, Pune have amply proved that sur
face drip irrigation is superior to subsurface drip irrigation. The surface drip sys
tem is shown in Fig. 12.2. The water carrying lateral pipes are placed on the soil
surface close to the plant and emitters are fixed at regular intervals to discharge
water at required rates. Water so delivered wets the root zone and there are no
water losses. The water saving is to the extent of 50—60%, yield increases by 12 -
30% and sugar recovery improves by 0.5 to 1.0 unit. In the subsurface system, the
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Sugarcane in agriculture and industry
lateral pipes are buried in the soil near the root zone and water is delivered in trickles. The bi-wall system of irrigation is a subsurface system. Surface drip irrigation is far better than the subsurface system. The fertiliser tank (Fig. 12.2) is employed to apply fertilisers (fertigation), chemicals (chemigation), and herbicides (herbigation). Drip irrigation is used under well or tank irrigation where water is scarce. Poor quality water such as saline water can also be used for irrigation. But, dripper clogging is frequent, due to salt encrustation. This can be managed by regular acid treatment. It is done by feeding 30% hydrochloric acid through venturi into the drip system until the pH of the farthest emitter is below 4.0 and then leaking it overnight and flushing. Drip tubes and drip tapes are better devices but their disposal after the crop cycle can become an environmental issue.
Fig. 12.2 Field layout of the drip irrigation system
Drip irrigation has many disadvantages like clogging of the emitters, damage by rodents and damage to the system during cultural operations. Due to the de
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12 Water management
velopment of surface feeder roots, cane is bound to lodge severely. The system
requires considerable skill to install and operate. At present the cost of drip sys
tems ranges from Rs 50,000 to Rs 80,000 per hectare depending upon the type of
system and the size of the field. To be cost-effective, the minimum cane yield
under drip systems should be 250 t ha -1 . Paired row planting as well as four row
planting is proving more beneficial under drip systems.
1 2 . 6
DRAINAGE
Irrigation and drainage are inseparable. Removal of excess water on the soil sur
face is termed 'surface drainage', while the removal by downward flow through
the soil profile is referred to as 'internal drainage'. Sugarcane needs at least 10%
aeration for root respiration. Moreover, sugarcane cannot stand 'wet feet' for a
long time. In ill-drained soils, cane shows yellowing and curling of young leaves;
adventitious roots are formed with restricted root system—yield and quality are
lower. Poorly drained soils are associated with low soil temperature and reduced
microbial activity. The greatest disadvantage of poorly drained soils is that
trafficability is reduced which hinders cane haulage. Clements (1980) demon
strated that in ill-drained soils cane 'freckling' occurs which is a symptom of Si
deficiency and toxicity of Fe, Mn, and Al. Application of calcium metasilicate is a
corrective measure to reduce the toxicity of Fe, Mn, and Al, and control sugarcane
freckling. The application rate of calcium metasilicate is 1.0 to 1.5 t ha - 1 in acidic
ill-drained soils.
Drainage of sugarcane soils can be improved by surface or subsurface drains.
The cheapest method is to have the surface drains at regular intervals and drain
the water at a common outlet. In some cases, if a common outlet is not available,
the drained water has to be pumped out. Tile or tube drainage can be used suc
cessfully to improve internal drainage and lasts for several years although initial
costs are high. Perforated clay tiles are cheap and can be used with advantage in
heavy black soils. Some layout designs for sugarcane field drainage are given else
where (Hunsigi, 1993a).
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Sugarcane in agriculture and industry
P l a t e 12 .1 Drip system
P l a t e 1 2 . 2 Layout
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12 Water management
205
P l a t e 1 2 . 3 Fertiliser mixing tank
Managing the ratoon cane
13.1
RATOONING DEFINED
The origin of ratoon is obscure but a century ago an unknown Hawaiian farmer recorded that only good ratoons pay. But the earliest ratoon seems to have started in Fujian province, East China in 1727. The word ratoon seems to originate either from Latin word retenus or Spanish word reteno or the French word rejeton. Essentially, ratoon cropping implies more than one harvest from a single planting. Thus, early man's observations in the regrowth of grassland as a basis for multiple harvest from the original root system has led to ratoon cropping in some crops including sugarcane (Plucknett et al., 1970).
It is difficult to estimate the area under ratoon cane either globally or regionally. There could be as many as 6 to 8 successive ratoons, as in Taiwan or just a single ratoon (plantooning) as in Hawaii due to soil problems and mechanical damage to stools. Ideally, in a plantation the ratoon and plant crop should make up 3 3 % and 67% of the total cane area respectively.
1 3 . 2
WHY RATOONS?
There is an old cliche that ratoons only pay and to ignore a ratoon is to ignore the
provenance of nature. The quintessence of ratoon cropping is shorter crop cycle,
reduced cost of production (particularly seed) and better utilization of climatic
conditions, especially the monsoon. Ratoons help to extend the grinding period
of sugar factories for they mature earlier than the plant crop due to early dehydra
tion of tissues and flushing out of N.
In terms of energy consumption, Kishan Singh (1981) observed that produc
tion of one ton of ratoon cane requires 89.04 million calories while 204.55 mil
lion calories is needed by the plant crop. The most important advantage of ra
tooning is its economic production. There is a clear saving of 5-7 t ha - 1 of seed
material. One survey has indicated that plant cane requires 482 man days as
against 295 for ratoon crop. There is a net saving of 13-15% in the total cost of
production.
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13 Managing the ratoon cane
Ratoons are not bereft of limitations. In fact, they are inferior bio types evolved, in the ecological mosaic and have many disadvantages—build-up of pests, diseases, weeds build-up, runout of commercial varieties, and poorer utilization of applied fertilizers, especially nitrogen. To produce a ton of cane from plant and ratoon, the N required is 0.97 kg and 1.99 kg respectively (Lakshmikantham, 1983). Ratoons contain more pith and fibre than the plant crop. Not only does arrowing commence early but it is perhaps more in ratoons than in the virgin crop. In some varieties like Co 419, Co 62175, and Co 4 2 1 , water shoots or 'lalas' (bull shoots or suckers) are more in ratoons than in plant crop.
In general, ratoon yields tend to be lower with reduced juice quality compared to plant cane, though there are exceptions to this rule. But the greatest disadvantage of ratoon is its restricted stubble root system. Van Dillewijn (1952) has alluded to the rope system of ratoon stubble roots which is less efficient in absorbing water and nutrients. Several investigations led to the convincing conclusion that the absorption of major and minor elements at the critical stages is restricted (depends on the formation of shoot roots) with a transient symptom of ratoon chlorosis (Hunsigi, 1993a, and Humbert, 1968).
1 3 . 3
THE ROOT SYSTEM IN RATOONS
A study of the root system in ratoons is of special significance, because response to
cultivation, fertilizer application, and water management depends to a great ex
tent on the stubble roots of ratoon . The special features of ratoon root system are:
(a) Ratoons have a shallower root system than the plant crop as far as the ab
sorbing part is concerned (Peng, 1984).
(b) The shoots of successive ratoons originate at higher levels than those of the
plant crop; hence ratoons have less anchorage and are more susceptible to
lodging and water stress.
(c) Initially, ratoons start functioning on the old stubble roots which is essen
tially a rope system (Van Dillewijn, 1952). The old stubble root is less effi
cient in absorbing nutrients and water because it is highly suberized.
(d) In the beginning, the functional white succulent shoot roots of ratoons are
very much restricted.
207
(e) The transition period between the decay of stubble roots and the initiation of new shoot roots depends on soil and climatic conditions, and may vary from 6-8 weeks. The old root system gradually ceases to function and decays. Under tropical conditions, a ratoon will have developed its own root system in 2 - 3 months.
(f) The trend of tiller production closely follows the pace of shoot root formation (op. cit.). Hence the presence of late tillers is an indication of a vigorous root system.
A detailed examination of the root system of ratoons of Co 62175 in red soils of Mandya (alfisols, xeralfs) was carried out adopting the method of Evans (1935) by using a jet of water. During the first, 3—4 weeks after stubble shaving, more than 90% of the root system comprised stubble roots. The lateral spread of stubble roots was 1.76 m and the depth was about 1 m. White new shoot roots just begin to form. The stubble roots show great ramification, are darker in colour, highly suberized, and less efficient. Humbert (1968) demonstrated rather convincingly that the absorption of 32P was limited due to stubble roots. Similar observations were made at the ISSR, Lucknow.
Operations like 'off-barring' or shoulder breaking coupled with heavy early earthing up are advocated to facilitate the decay of stubble roots and ensure early formation of shoot roots. The decaying stubble roots may temporarily immobilize nitrogen and reduce its availability to the crop. Immediately after the harvest of the first crop, stubble shaving is done to encourage the development of vigorous shoots at the ground level, ensuring synchronous tillers with firm anchorage. However, these operations are not recommended in many sugarcane growing countries like Australia, South Africa, Taiwan and many parts of Latin America. Torres and Villegas (1995) demonstrated that the use of tynes seemed to have a detrimental effect due to root pruning which adversely affected the growth of succeeding ratoons in the wet mollisols of Columbia.
Soil compaction has a detrimental effect on ratoons. Srivastava (1981) studied the relevance of soil compaction in ratoon management. Taking more than one ratoon resulted in deterioration of soil physical conditions as judged by Bulk Density (BD) values and per cent pore space (entisols) (Table 13.1).
The ideal bulk density of sugarcane soils is 1.2 to 1.3 kg m-3. Similar observations were made in vertisols of Kolhapur region.
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Sugarcane in agriculture and industry
13 Managing the ratoon cane
Another disadvantage of ratoons is their imbalance in the shoot-root ratios at the beginning; the optimum ratio of 15 to 20 is attained at a much later stage. Chapman (1988) suspected that the old root system eventually may provide an unfavourable rhizosphere to the new root system.
Table 13.1 Effect of number of ratoons an bulk density values (BD) and % pore space
Soil depth BD kg m-3 (Co 1148) (cm) IRC II RC III RC IV RC
0-15 1.48 1.59 1.61 1.48
16-30 1.57 1.62 1.63 1.54
31-45 1.63 1.65 1.73 1.56
46-60 1.67 1.67 1.76 1.61
% pore space
0-15 43.8 40.0 39.2 43.8
16-30 40.0 38.8 38.5 41.9
31-45 38.5 37.7 34.7 41.1
46-60 37.0 37.0 33.6 39.2 Source: Srivastava, 1989.
13.4
FERTILIZATION
13.4.1 Ni t rogen
Nitrogen is a key nutrient and influences the yield and quality of the cane. It is known to increase the primary sources, i.e. leaves, tillers, and dry matter production. Adequate and early N fertilization is highly essential for ratoon cane to obtain the desired objectives of high cane and sugar yield. But research has amply demonstrated that to produce 1 ton of ratoon, nearly double the dose of N is
209
210
Sugarcane in agriculture and industry
required as compared to the plant crop. The data of Chow and Samuels (1977) show that the Nitrogen Use Efficiency (NUE) was 1111 kg cane per kg N applied for the first crop and the values for the successive ratoons decreased to 1020 and 902 kg cane per kg N. Leaf N dropped more in ratoons than in plant crop. Nitrate reductase activity in the leaf lamina is lower in ratoon than in plant cane (Rai er al., 1989). Hence higher dose of N is required to produce more sugar from ratoons than plant cane. Limited experiments conducted in the Mosso region of Burundi (Central Africa) showed that the response to N was consistent but was linear in the first ratoon and curvilinear in the second ratoon (Hunsigi, 1993a). There was no residual effect of N in subsequent ratoons. At best 2 to 6% residual N is used by the ratoon crop (Ng Kee Kwong and Deville, 1987). Therefore, Zende (1990) advocated a soil log of 40 ppm N O 3 - N throughout the crop cycle to ensure an optimum yield of plant crop and successive ratoons.
Sundara and Tripathy (1999) established convincingly that in multi ratooning (one PC + 3 RC) Soil Available N (SAN) declined sharply by 26 .3% at the end of the third ratoon (Table 13.2). Sugarcane varieties influenced SAN levels; high yielders depleted SAN more than low yielders. Additional N to the tune of 2 5 % of the recommended dose improved SAN levels. N losses are more pronounced in multi ratooning. Thus, additional N application, trash mulch and subsequent decomposition by cellulolytic bacteria (spreading cow dung slurry) are the suggested remedial measures to increase SAN levels under multi ratooning (op. cit.).
Table 1 3 . 2 Mean Soil Available N levels (mg kg-1) under multi ratooning in
tropical vertisols
Measure After I Ratoon II Ratoon III Ratoon merits plant crop
Mean of 103.3 98.1 94.1 87.1
12 Cvs
lsd .05 4.2 2.8 3.6 3.2
Source: Sundara and Triparhi, 1999 partially modified, Initial soil available N 118.2 mg kg-1
Globally, the average range of responses varied from 0.05 to 0.21 kg -1 N applied.
Still greater responses are anticipated in highly N-deficient soils. An increased
ratoon yield following N addition is attributed to the increased number and weight
13 Managing the ratoon cane
of millable stalks. A reduced NUE in ratoons is ascribed to an imbalance in the shoot-root ratio at the juvenile stage, delayed shoot-root development, and relatively inefficient stubble roots.
Gascho et al. (1986) demonstrated that with a normal rate of N application, ratoon yields are far less than the plant crop yield (Table 13.3).
Table 13.3 Effect of N rate on the yield and its attributes in plant and ratoon canes
Nrate Millable Stalk (Yield t ha-1) (kg ha-1) stalks weight Cane Sugar
(x103ha-1) (kg)
Plant crop
0 34.2 0.52 24.1 3.1
56 45.3 0.56 29.7 4.0
112 41.2 0.57 27.7 3.9
224 47.7 0.59 32.7 4.4
Ratoon crop
0 27.0 0.39 15.5 1.7
56 35.4 0.50 20.3 3.0
112 39.0 0.52 20.3 3.0
224 50.0 0.66 36.8 5.5
448 58.5 0.67 42.9 5.9
896 42.8 0.63 33.3 4.0
Source: Gascho et al., 1986.
This is attributed to lowered internal and external NUE in ratoons compared to the plant crop. The internal NUE is defined as one kg of sugarcane or sucrose per kg of N accumulated in the above ground portion. External NUE is one kg of sugarcane or sucrose per kg of applied N. In a recent study of sugarcane (cv. Co 7804) grown in red sandy loam soil of Mandya (alfisols, xeralfs), it was observed that ratoons not only had less internal or external NUE, but lowered N-harvest index (HIN) (Table 13.4).
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Sugarcane In agriculture and industry
It is to be noted that the external or internal NUE and HI N declined as the
applied N levels increased.
Table 13 .4 External and internal nitrogen use efficiency (NUE) and Nitrogen
harvest index (HIN) of plant and ratoon cane (First ratoon cv. Co 7804)
N Levels External Internal N-Harvest Index
(kg ha-1) NUE NUE HlN
Plant
150 1.207 1.418 0.650
250 0.813 1.291 0.540
375 0.526 1.129 0.530
Ratoon
150 0.814 1.058 0.380
250 0.661 0.782 0.380
325 0.624 0.685 0.400
Note: Nitrogen harvest index (HIN) = Nitrogen content in stem (kg)/total N uptake (kg)
Source: Hunsigi, 1993b.
Response to applied N also depends on the cane cultivars. It was observed in red sandy loam soil of Mandya that cultigen Co 7804 is more responsive to N than Co 419. Similar observations were made by Gascho et al. (1986), who observed that CP 65-357 gave higher response to N in terms of both cane and sugar yield. This cultivar has the highest NUE. The authors advised that the NUE can be enhanced by the selection under low N conditions.
Conscious efforts were made to improve NUE in ratoon cane by the use of slow-release N fertilizers. But the results are not consistent. Zinde (1990) had shown that urea blended with neem cake (cake made from seeds of Azadirachta indica) proved to be effective and he recommended a blending of 300 kg N as urea with 140 kg neem cake (-10-12% neem oil). However, studies in red soils of Mandya have shown that point placement of Urea Super Granules (USG) resulted in an extra yield of 17 t ha-1 over an average of 4 seasons (Table 13.5).
212
213
13 Managing the ratoon cane
Table 13 .5 Effect of urea vs USG on ratoon cane yield (t ha-1) in Co 62175
N Source Plant crop IR 2R 3R 4R 1979-80 1980-81 1981-82 1982-83 1983-84
Urea 125 99 94 100 90
USG 124 109 112 109 102
Increase
over USG 1 10 18 9 12
Source: Hunsigi, 1993a.
Extensive field studies have shown that in some soil types associative N fixation termed 'diazotrophic rhiozocoenosis' results in the addition of over 75 kg N ha-1 (Boddey et al., 1991). The promising N fixers are Azospirillum and Azotobacter, and cane cultivars differ in their response to these bioagents. The data presented in Table 13.6 reveal an interaction between N levels and biofertilizers.
Table 13.6 Interaction between N levels and biofertilizers (cv. Co 62175 grown in alfisols, xeralfs)
N levels Cane yield (t ha-1) Untreated Treated with Azospirillum Mean
Azotobacter
125 148 152 154 151
250 199 203 207 203
375 194 198 200 197
Mean 181 184 187 -
lsd 0.5 - 6.04 - -
C V % - 2.76 - -
Note: Biofertilizers at 25 packets, each of 200 g (5 kg ha-1) were applied to the soil.
Source: Hunsigi, 1993b.
It is evident that Azospirillum is slightly superior to Azotobacter. It is obvious that their effectiveness reduces with the increase in N dosage. The study further
Sugarcane in agriculture and industry
suggested that Azospirillum being micro-aerophillic, is more suited to compacted
ratoon soils.
Another sure way to improve NUE is the incorporation of intercropped leg
ume residues like French beans, sunnhemp, greengram or soyabean. Both the
quality and quantity of biomass incorporated in soil determine the improvement
in ratoon cane yield (Table 13.7).
The biomass incorporated in soil should be succulent, high in N content, and
easily decomposable. Incorporation of legume residue is associated with increased
mineralizable N (-200 kg ha - 1) for upto 6 months and with increased dehydroge
nase activity (30-35 μl H, evolved per 5 g soil). The data in Table 13.7 reveals
that there is a saving of 50 leg N ha - 1 and at a higher N level, the effect of residue
incorporation is diminished.
Response of ratoon cane to applied N has been well described by Hunsigi
(1989). Among the several models tested such as Mitscherlich, power functions,
etc. the second degree polynomial predicted the ratoon yield to N levels in most
soils.
Table 13.7 Effect of incorporation of legume residue on yield (t ha - 1) First ratoon
of Co 419
Treatment N levels (kg ha - 1 )
200 225 250
1. Incorporation of legume 156 159 152
residue (mean vield of 4
intercrops)
2. Entire cane 111 138 147
Increase of 2 over 1
treatment (%) 28.8 13,2 3.3
Source: Hunsigi, 1993a.
13.4.2 Phosphorus
Clements (1980) reiterated that ratoons require nearly double the amount of P
compared to the plant crop because they have to start the root system denovo.
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13 Managing the ratoon cane
Phosphorus is essential to hasten the formation of shoot roots and increase tillering
of ratoons. But its availability depends on the fixation of native and applied P. To
circumvent this problem, it is suggested that P should be applied in localised
concentrations through carriers like compost, FYM, bagasse, etc. Workers in South
Africa felt that top dressing of P over cane trash was more effective in ratoon cane.
Similarly, Pelwatte Sugar Co. Ltd., Srilanka advocated P application to trash
blanket.
Among the sources of P, concentrated triple super phosphates (44—52% P 2 O 5 )
are used in the sugar industry. If sulphur deficiency is anticipated, then single
super p h o s p h a t e is used. The greater effectiveness of rock phosphates
(27—41% P 2 O 5 ) with a fineness of 100 mesh (150 μm) in acid soils is well recog
nised. The ratoon crop benefits from the residues of P applied to plant cane
(Fig. 13.1). The data in Fig. 13.1 indicates a progressive decrease in the advantage
derived by the ratoon from the soil built-in P. This is possibly due to early shoot
root formation.
Fig. 13.1 Performance of successive ratoon on plots containing substantial
residues of P applied to plant cane (+ RP) and without residual P (-RP)
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In general, the response of ratoon cane to P dressing is more consistent than
that of plant crop and 1 kg P 2 O 5 results in a response ranging from 0.035 to
0.075 t ha - 3 . Nevertheless, lower concentration of P is recorded in cane leaves of
ratoon crop than in the planted cane. As regards the efficiency of applied P, both
plant and ratoon crop seem to behave similarly. The improved yield following P
application is attributable to increase in tiller production, weight per cane, and
final stalk population. Addition of P tends to increase the pol in juice at an opti
mum P level; besides, juice purity is enhanced.
The recovery of added P is barely 20% due to its fixation. Hence, efforts should
be made to improve P-use efficiency through Vesicular-Arbuscular Mycorrhizae
(VAM) and P-solubilising bacteria. Fox and his associates (1990) contended that
sugarcane is least mycorrhizae-dependent. The species of Pseudomonas, Bacillus
and Streptomyces are the major microbes responsible for P solubility. Among the
fungi, Aspergillus niger, A. flavus, and Aspergillus awamori are known to solubilise
P. Recent studies have shown that phosphobacterin Bacillus megatherium
var. Phosphaticum improved the yield and quality of both plant and ratoon cane
when it was mixed with rock phosphate.
Filter press mud (PM) is an important source of P fertilizer. Prasad (1976)
advocated thai the application of 20 t h a - 1 PM is optimum and increase in cane
yield ranges from 30-60% in plant and ratoon cane. There is an improvement in
sugar yield following PM application. Investigation in Mauritius (Ng Koe Kwong
and De Ville, 1988) and Cuba (Arzola and Carrandi, 1982), confirm these results
and suggest that PM increases organic matter content of soils with enhanced N
uptake. Press mud is a better source of P than triple super phosphate and supplies
both secondary and minor elements. At Bacita Sugar Estate, Nigeria, PM with an
average composition of N (1.05%), P (0.47%) and K (0.68%) at 10-20 t h a - 1 in
conjunction with recommended fertilizer dose ensured highest cane and sugar
yield besides sustainable productivity.
13.4.2 Potassium
Adequate K in the root environment is a sine qua non for successful production of
ratoons. The agronomic value of K rests with the increase in volume of cane,
[Volume of cane, V= π x L x D x 3/4; where L = length of cane (cm), D = Diameter
(cm)] which in turn reflects the improved girth and weight per cane.
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13 Managing the ratoon cane
Potassium is also associated with cane quality as it improves pol per cent in cane. A good response to applied K was observed in red, mixed red and black soils, but the response is doubtful in alluvial soils as they contain K-bearing minerals like illite. Threshold values of exchangeable K, in neutral ammonium acetate for sugarcane range from 65 to 150 ppm (Duflo, 1976). In South Africa, this value was raised to 225 ppm in heavy textured soil. We assert that exchangeable K per se is a poor index of K availability in continuous cropping as in sugarcane ratoons. Hence, a portion of non-exchangeable K but plant available fraction termed the 'Step-K' should be included along with the labile pool to predict satisfactorily the K availability to ratoon cane. This is further confirmed by Wood and Shroeder (1992) who have employed 0.1 m BaCl2 as soil K extractant, which extracts non-exchangeable K from inter-layer sites of clay mineral. They concluded that BaCl2 extraction has led to improved K prediction for sugar industry soils.
The response to applied K in red, mixed red and black soils range from 0.06 to 0.117 t ha -1 kg -1 K2O at an optimum level of K2O 100-120 kg ha - 1 . However, in heavy textured soils, the K response decreased progressively, a phenomenon which may be associated with soil compaction, decreased aeration, and consequent restricted root growth.
Interaction between the major elements in ratoons is noticed. Potash addition in the presence of P improved both yield and quality of cane in red, mixed red and black soils. In view of such positive interactions, Humber t (1978) suggested an optimum NPK ratio of 2 : 1 : 2. Duflo (1976) suggested N : K ratio of 1 : 1.7. It is generalised that for ratoons NPK ratio of 1 : 0.7 : 1.5 seems optimum.
The response of varieties to applied NPK levels in planted and ratoon cane differs significantly.
Figure 13.2 depicts the overall response of the varieties (plant and ratoon) to composite NPK levels and shows that ratoons have a response pattern similar to that of plant cane but their yield potentials are of a lower order.
A generalised response of ratoon cane to three major elements is depicted in Fig. 13.3. The range of response is more with K followed by N and P. It is further observed that the Mitscherlich equation and Cobb-Douglas function failed to predict satisfactorily the response of ratoon cane to applied NPK fertilizers. However, the quadratic and square root models satisfactorily explained the nature of response to applied major nutrients (Table 13.8).
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Sugarcane in agriculture and industry
218
Table 13.8 Response models of ratoon cane to applied NPK
Fig. 13.2 Response of plant and ratoon cane to NPK fertility levels
13 Managing the ratoon cane
Fig. 1 3 . 3 Range of response of ratoon cane (t ha l) per kg of N, P 2 O 5 , and K2O at their optimum levels of application
13.4.3 Secondary, minor, and beneficial e lements
Micronutrient or trace elements are required in small quantities, yet play a pivotal role in plant growth. These invariably have synergestic or antagonistic effects with other nutrients. Secondary elements which usually interact with other micronutrients and have large influence on yield and quality of cane are Ca, Mg, S, and Si. Other micronutrients like Na and C1 are known to regulate water relation (osmoregulatory) and influence sugar output. The information on this aspect is sketchy.
In the early years of the fertilizing practice for continuous cropping with sugarcane, these minor and secondary elements were 'incidental'. But monoculture of cane, lack of addition of organic matter, and use of high analysis fertilizers led to the deficiency of minor/secondary nutrients in some regions. Hence this requires
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corrective measures. A permanent solution could be the rendition of cane with prolific surface and subsurface feeder root system to exploit micronutrients present
in the soil.
In acid soils, deficiency of Ca and Mg is usually encountered. Hence applica
t i o n of limestone at 1-3 t ha - 1 to the plant crop improves the yield of subsequent
ratoons. But it is caut ioned that excessive liming reduces the uptake of Mg, K,
and other minor elements with a concomitant decrease in yield and sugar output.
Ca acts as an ameliorate/conditioner; Mg is more a nutrient. Qu-Ming and Ju-
Ming (1986) reported that vast areas of Fujian province of China are deficient in
Mg and respond to addi t ion of Mg.
Liming improves the yield and quality of cane grown in acid soils. In Belle
Sandy Phase, Bacita Sugar Estate, Nigeria, liming at 10 t ha - 1 has increased cane
and sugar yield of ra toon crop (Table 13.9).
T a b l e 1 3 . 9 Effect of lime on yield and quality of cane (First ratoon, Cv. Co
997), Belle Sandy Phase, Bacita Sugar Estate, Nigeria
220
Source: Pers. commn. S. P. Jaiswal.
Similarly in acid soils of Thiruvilla, Kerala, lime applied to the plant crop
improved the yield a n d quality of ratoon cane (Hunsigi, 1993b) (Table 13.10).
13 Managing the ratoon cane
Table 13.10 Effect of lime on yield and quality of ratoons in acid soils of Thiruvilla, Kerala, India, applied to plant crop
Source: Hunsigi, 1993b.
LR—Lime requirement, NS—Non Significant
Sulphur is the fourth important nutrient for sugarcane next to N, K, and P. Its deficiency is increasingly widespread. The typical deficiency symptoms are interveinal chlorosis and anthocyanin pigmentation on leaf margins. Leaves become narrower, shorter, and pointed (Tandon, 1991). Canes are thinner and taper rapidly at tips. Ratoons are more susceptible to S deficiency than plant crop (loc. cit.).
In a more systematic study, Fox (1976) has found the internal (40 kg S ha-1) and external (10 kg S ha-1) requirement of S for cane. In another significant contribution, Ghosh et al. (1990) observed that S is directly connected to N utilization with associated improvement in NUE. Increased NUE due to S dressing is possibly due to increased in vivo nitrate reductase activity which is a key enzyme for the entry of N into the plant system. Positive and significant S x N interaction
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Sugarcane in agriculture and industry
is being noticed. Sulphur also acts as a slow release N fertilizer. Sulphur coated
urea provides sustained N supply. With an emphasis on recycling of industrial
wastes, PM from sulphitation process is better than carbonation process. Wher
ever severe S deficiency is observed, 20—30 kg elemental sulphur is mixed into the
soil prior to planting, which takes care of subsequent ratoons.
Iron deficiency cannot be seen in isolation. Hence, Fe-Mn interaction is con
sidered. True iron deficiency is a rarity under field conditions. But lime, CO 3 ,
H C O , , P and heavy metal induced iron chlorosis is of frequent occurrence. Ra
toons are more prone to Fe deficiency due to restricted root system in the initial
stages. In acid soils, Fe-Mn interaction is well documented. In a normal cane
Fe : Mn ratio is 15 : 1 or greater, whilst, Fe deficiency/Mn toxicity is associated
with a ratio of 1 : 1 or even less (Evans, 1959).
Iron deficient plants have an accumulation of Fe in the nodal region but the
mobility in the tissues is very much restricted. It is reasonable to postulate that the
inactivity of Fe in the tissues is due to the high pH of cell sap which is primarily
responsible for iron chlorosis. Ratoon chlorosis observed in red soil of Mandya is
due to Fe deficiency. But it is transient and this nutritional disorder is observed
when plant crop is harvested leaving large butts or planted shallow. In general, Fe
deficiency can be ameliorated by 25—30 kg FeSO4 soil application or 2 kg FeSO4
as foliar spray. Iron chelates are more beneficial.
Manganese differs from the other elements in that both deficiency and toxicity
can be seen under field conditions (Jones, 1985). Interveinal chlorosis and small
pointed leaves in ratoons are a distinct symptom of Mn deficiency.
Zinc deficiency in sugarcane plant/ratoon is frequently seen in South and South
East Asia where cane is taken in rotation with flooded paddy rice. The deficiency
symptoms can be recognised by the stunted growth and patchy appearance. Liming
induces Zn deficiency and its solubility decreases as pH increases. Antagonism
between Zn and P is well documented. Besides P, high concentration of Fe, Mn,
and specially Cu causes severe Zn deficiency. This, however, can be overcome by
soil application (20-25 kg ZnSO 4 ha -1) or foliar spray (1-2% ZnSO 4 ha - 1) . Foliar
spray is superior to soil application.
The deficiency of other micronutrients like Mo, CI, Cu, and B in C4 plants is
practically unknown in field-grown conditions (Jones, 1985). Bowen (1972) ob
served that the level of C1 in sugarcane is quite high for CI to be recognised as a
major element.
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13 Managing the ratoon cane
Silicon is a beneficial element. Paddy and sugarcane are highly siliciferous plants and the importance of Si has been recognised since the time of Liebig. Saccharum and the allied genera Miscanthus and Erianthus are Si accumulators (Jones, 1985). It is absorbed as silicic acid [Si(OH)4] by an active process. The multiple effects of Si include rise in soil pH, improved P nutrition and water relation in plants, and reduced uptake of Mn, Fe, Zn, and other heavy and toxic metals. It is instrumental in disease resistance, reduces lodging and improves stalk length in cane. 'Freckling', a necrotic leaf spot condition, is a symptom of low Si in sugarcane receiving direct sunlight. But Si addition ameliorates this malady since it filters harmful ultraviolet radiation (Tisdale et al., 1990). Recent evidence affirms that silica cells in sugarcane provide 'windows' in the mesophyl tissues, thus improving light interception and CO2 fixation, leading to high growth rate and increased sugar accumulation. It is well documented that Si suppresses the activity of invertase, peroxidase, polyphenol oxidase, and phosphatase (loc. cit.). The reduced activity ratio of acid invertase to natural invertase (AI/NI) is evident following sodium meta silicate sprays (Hunsigi, 1993b).
Table 13.11 Response of first ratoon to silicate rates (Cv. CP 63-588)
Source: Elwad et al., 1882.
To ascertain the role of Si, experiments were conducted by Elawad, et al. (1982) with TVA and Florida slag as sources of silicon. These materials contain 16-24% Si and 16-18% Ca as well as other essential minor elements. Irrespective of the source, Si application to low silica soils, such as histisols, improved yields of cane and sugar (Table 13.11). An increased cane yield following Si addition was attributed to the increases in plant size, plant height, stem diameter, stalk density, and
223
224
Source: Eiwali, and Gascho, 1984.
Sugarcane in agriculture and industry
improved photosynthetic efficiency (Table 13.11). The applied Si improved leaf chlorophyll content and corrected leaf 'freckling'. The authors concluded that Si is necessary for normal growth of plant/ratoon and that leaf 'freckling is a symptom of its absence. The optimum rate of application of silicate material for ra-toons is 5-15 t ha-1 (Elawad et al., 1982).
13 .5
FOLIAR DIAGNOSIS
Crop log was introduced by Clements (1980). Crop log is a record of progress from the start until the arrival at harvest. Crop logging is successfully used to monitor, evaluate or schedule fertilizer application to maximise crop production. This approach has been contested in recent times. Soil tests remain an excellent pre-plant practice and Critical Nutrient Levels (CNL) are good guides for scheduling fertilizer application to plant crop. But its reliability is questioned for successive ratoons (Elwali and Gascho, 1984). Recent research seems to be in favour of nutrient ratios rather than the CNL approach. Hence Diagnosis and Recommendation Integrated System (DRIS) seems to have an edge over the Clements/ Hawaiian crop log approach. Eiwali and Gascho (op. cit.) pointed out that DRIS is suitable for successive ratoons as a foliar diagnostic technique and is a better guide to fertilizing cane. They obtained higher cane and sugar yield when the fertilizer dose was based on DRIS, rather than on soil test values or the CNL approach (Table 13.12).
Table 13.12 Effect of soil testing, CNL approach and DRIS system on Ratoon cane and sugar yield
Improved yield is attributed to late application of both major and minor elements as revealed by DRIS.
The relation between DRIS index and N levels in plant and ratoon crops of Bo 91 grown in alluvial soils (aridisols, calciorthids) is shown in Fig. 13.4. It is seen that ratoons tend to have more negative DRIS values than the plant crop confirming that ratoons are less efficient utilizers of N than plant crop.
Fig. 1 3 . 4 Relation between DRIS index and N levels in plant and ratoon crop (cv. Bo 91) in alluvial soils of Pusa, Bihar
Advances in foliar analysis technique are provided by Schroeder and co-workers (1995). According to them, DRIS is more appropriate for young cane. This provides corrective fertilizer treatment to the current crop. And leaf analysis of ratoon cane is subsequently used for evaluating the correctness of the original advice based on soil tests (loc. cit.).
DRIS is specially suited for micronutrients as antagonism (P-Zn) or synergism (S—N) is more prevalent. As an illustration, DRIS indices of ratoon cane obtained by Elwali and Gascho (1984) are presented in Table 13.13. The DRIS indices may be positive or negative but their sum is always zero. The most negative index indicates the nutrient most required and most positive index indicates the nutrient
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Source; Eiwali, and Gascho, 1984. Partially adopted.
The Nutrient Balance Index (NBI) presented in the last column is the measure
of balance among nutrients in each field. Thus NBI is obtained by adding the
values of DRIS irrespective of sign. The larger the value of NBI the greater is the
imbalance among nutrients.
1 3 . 6
TIME AND METHOD OF FERTILIZER APPLICATION
Studies in Australia have shown that the plant crop takes 3.5 to 5.0 months to
'close-in' compared to 3 to 3.5 months in ratoon. The fertilization schedule should
be completed before the 'rapid-close-in' period. Hence early fertilization to ratoons
is obvious.
Table 1 3 . 1 4 Fertilization schedules for ratoon cane
Single basal application after Two equal splits: Immediately harvest of crop after harvest and 3-4 weeks later
Medium and heavy black soils Very sandy and sandy loams with high CEC
Early maturing, short duration Late maturing and non-flowering varieties and drought tolerant varieties
Co C 6 71, CoJ 64, CoC 90063
High tillering varieties wirh initial Low tillering varieties with low initial vigour vigour
e.g.: N C O 310, N C O 376, Heavy rainfall and coastal regions B 37172, Co 62175, Q 58 Co 7804, Co 86032, Co 8371
226
least required. An index close to zero suggests that the nutrient concerned is present
in adequate supply.
Table 1 3 . 1 3 DRIS indices of ratoon cane in Histisols of Florida
13 Managing the ratoon cane
To improve the fertilizer use efficiency, time and method of application assume
great importance. Band or point placement to the stool is recommended as this
ensures easy availability of nutrients through mass flow and diffusion. Some broad
generalizations on the time of fertilizer application to ratoons are given in Table
13.14. Employing 15N labelled fertilizer, Ng kee Kwong and Dieville (1995) dem
onstrated the superiority of a single application at grand growth stage or in two
equal splits. N carriers had little effect on N recovery.
1 3 . 7
YIELD ATTRIBUTES OF RATOON CANE
An attempt was made to find out the yield components of ratoon cane which can
be manipulated through agronomic, physiological, and genetic means. It was ob
served that the yield attributes like cane length, girth, and weight per cane have
substantial contributions towards ratoon yield (Cv. Co 7804) and the situation is
represented in the multiple regression equation:
y = - 1 1 0 + 6.8363 X1 + 25.8352 X2 + 607.0244 X3,
+ 0.0430 X4(R2 = 0.955)
where Y= ratoon cane yield (t/plot)
X1 = cane length (cm)
X2 = cane girth (cm)
X3 - cane weight (kg)
X4 = cane population per plot
The combined effect of these yield attributes contributes nearly 96% of the
variation in yield. It is worth noting that the weight per cane and cane girth have
a greater contribution than the stalk density and cane length as is evident from the
significant slopes associated with these parameters. The path coefficient analysis
is depicted in Fig. 13.5. It is seen that cane weight has a direct contribution to
cane yield, while others have more indirect contributions.
Similar observations were made by Chapman (1988) who reported that the
stalk weight and stalk number are important ratoon yield determinants. While
explaining the yield variation in ratoon yield, Chapman (loc. cit.) concluded that
both Light Interception (LI) and Light Use Efficiency (LUE) declined in ratoon
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Sugarcane in agriculture and industry
crops. LUE is dependent on gross photosynthesis, Specific Leaf Nitrogen (SLN), temperature, and dry matter partitioning. Low LUE explains reduced stalk weight at harvest in ratoon crops.
Fig. 13.5 Path coefficient showing yield contributing factors in ratoon cane
The physiological basis of variation in ratoon yield is the shift in population dynamics. To start with, ratoons would have a plant density of 30 m -2, but there would be an exponential drop and the density stabilizes at 10-12 m -2. Tiller mortality is to the extent of 50-60% in the formative phases. The exact nature of tiller mortality needs to be unravelled. Perhaps, lack of light due to mutual shading causes high tiller mortality.
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13 Managing the ratoon cane
1 3 . 8
QUALITY: RATOON VS PLANT CANE
Ratoons mature earlier than the plant crop due to early dehydration of the tissues
and flush-out of N. This is why ratoons are preferred for milling early in the
season. The quality estimates of plant and ratoon cane (Table 13.15) are made by
the Pol Ratio (PR), namely, Tons Cane/Tons Sugar (TC/TS). And admittedly, the
lower the pol ratio, better the quality; PR values may range from less than 5 to
over 15 (Table 13.15).
1 3 . 9
CULTURAL REQUIREMENT
A great diversity exists in the cultural requirement of ratoons. In India, Kenya,
and Uganda, stubble-shaving and shoulder breaking or off-barring are advocated,
while these operations are totally dispensed with in countries like South Africa,
Australia, Taiwan, and in many Latin American countries. It is reasonable to be
lieve that in regions where manual harvesting is done, stubble-shaving has a dis
tinct advantage in promoting uniform, stout, and vigorous shoots. Further, shoulder
breaking opens the soil, permitting better aeration and water infiltration. This
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Sugarcane in agriculture and industry
facilitates the decay of old stubble roots and promotes early shoot root formation.
In Swaziland and South Africa, ripping and chiselling did not result in yield ad
vantage (Leibbrandt, 1984). It is a common truism that successive ratoons leave
the soil compact with increased bulk density and reduced porosity. Humbert (1968)
opined that root development was gradually retarded as the bulk density increased
from 1.1 g cc -1 to 1.6 g cc -1. Root proliferation and extension of roots practically
ceased at a bulk density of 1.9 g cc -1. In such compact soils, 02 potentials are low
with a subsequent reduction of water and nutrient uptake.
Thus, under most soil conditions, sub-soiling in the interrows of ratoons is not
worthwhile and a conventional plough depth of 20—25 cm is quite adequate
(Moberly, 1969). From his review, Soopramanian (per. commn.) concluded that
soil ripping or deep inter-row cultivation is of little value, except in heavy soils
where compaction is a problem. Conservation tillage has been recommended in
Australia, while minimum tillage through chemical ploughing using glyphosate
has been advocated by Iggo and Moberly (1975) in South Africa.
With respect to spacing, a closer spacing of 0.5 m is better than 1.0 or 1.5 m to
obtain higher biomass, cane, and sugar yields. On the other hand, closer spacing
creates problems with weed control (Shih and Gascho, 1980) and working with
machinery. The final banking up operation is done in many countries which greatly
contains lodging. This would be difficult in a closely spaced crop. As a practical
measure, 1.0 m spacing seems optimum in many sugarcane growing soils. Re
garding harvest time on subsequent ratoons, the general consensus is that they
should be harvested early. Ambient temperature, humidity, and other parameters
have a profound influence on ratoon yield and quality.
Trash handling is an important operation in ratoons. It is invariably burnt after
the previous harvest of the crop. But as environmental concerns are uppermost,
we recommend that a trash blanket be aligned in the cane rows, which inciden
tally controls weeds. One distinct advantage of trashing (putting trash on the soil
surface or trash mulching) is conservation of soil moisture. But trash does not
easily decompose due to high content of lignin and hemicelluloses. Hence a sug
gestion is made to add lime/superphosphate/press mud/urea or cowdung slurry
to act as starters and facilitate the decay and organic matter build up.
13 Managing the ratoon cane
1 3 . 1 0
NUMBER OF RATOONS
Mainland China has nearly three-centunes-old ratoons but this does not justify multi-ratooning, which is perhaps a contingency. And to take as many ratoons as feasible is an oversimplification of the complexities involved in ratoon cropping. In Venezuela, 9-20 ratoons and in Taiwan 7-8 ratoons are common. In Australia 2-3 ratoons are grown, while Hawaii adopts single ratooning (plantooning). Careful study by this author in Mosso region of Burundi (Central Africa), indicated that relatively more ratoons can be taken (4—6) in heavy alluvial soils than in light textured ferrisols. But even a single ratoon is improbable in saline/sodic/acidic soils. Interestingly, Blackburn (1994) has observed that the number of ratoons are controlled by a statute or by legislation in Barbados, Queensland, Java, and Taiwan.
Multi-ratooning can probably be practiced in well-drained deep soils with high native fertility. This calls for careful gap filling, judicious and timely application of organics (including green manure) and inorganics, trash mulching to conserve soil moisture, and a high level of management.
Fig. 13.6 Sugarcane crop cycle, Bacita, Nigeria
Figure 13.6 depicts the crop cycle observed in Bacita Sugar Estate, Nigeria (pers. commn. S. P. Jaiswal). It was suggested that ratoons are not economical beyond 4.The yield declining factors (FY) have been proposed by Brzesowsky (1986). These are:
FYP = 0, FYR 1 = 0.9, FYR 2 , = 0.85, FYR3 = 0.75, FYR4 = 0.65, FYR5 = 0.55 and FYR5 = 0.50
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Sugarcane in agriculture and industry
where P represents plant crop and R1 , R2, etc. are the first, second ratoons, etc.
The declining trend in subsequent ratoon yields is due to soil compaction, extent
of gaps, and pests and diseases associated with ratoons. In soils with 2 : 1 clay,
soils get compacted with decreased number of ratoons. Yields are reduced due to
restricted root system following reduced 02 potentials, water, and nutrient up
take. The decision to replant may also be guided by Breakeven Yield Difference
(BYD). Threshold cane yield may also be taken as a benchmark to decide replanting (Fig. 13.6). Shaw (1989) introduced Ratoon Performance Index (RIP) which considers the accumulated yield decline between a reference yield (annual average yield of plant/ratoon cane) and the yield of second to fifth ratoon. In monetary terms, replanting should be done when the value of the accumulated yield decline exceeds the planting cost (Soopramanian, G. C. pers. commn.)
Prudence, ecology, and economics dictate that the number of ratoons should be restricted and pulse crops be rotated for sustained productivity. Hence, Peng (1984) has asserted that in recent years, there has been a tendency to reduce the number of ratoons to no more than 2 due to an evident build up of injurious pests, diseases, and weeds.
13 .11
RATOONING POWER OF CULTIVARS
Good ratoon ability of cane cultivars is an essential prerequisite for success but many questions arise as to what makes one a better ratooner than the other ratooners. The significance of ratooning power was well recognised from the 1930s and varieties like Co 312, Co 205, and Co 285 were released for general cultivation. It was postulated that the varieties with a high content of Spontaneum plasma are better ratooners.
Eurgo, Co 419, Co 740, Co 6806, Co 6415, and Co 1158 proved to be better ratooners. The experience of this author has shown that B 37172, N: Co 310, and N C O 376 are good ratooners. However, cane needing special attention, thick cane like Q 49 is not a good ratooner. It was conjectured that high contents of both recoverable and reducing sugars in the stubble, induce ratooning power in successive ratoons. Findings of Shrivastava et al. (1981) confirm these observations (Table 13.16). Further, partitioning of dry matter in ratoons indicated that
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13 Managing the ratoon cane
the contribution of leaf and sheath was proportionately more in ratoons than in spring or autumn planted cane.
Table 13 .16 Sugar content, leaf, and sheath weight in planted and ratoon cane (Cv. Co 1148)
Source: Shrivastava et al. 1981. Data modified and adopted.
It is hypothesised that reducing sugars in stubble play a dominant role in imparting greater ratooning power to cultivars since they are utilised for respiration of newly emerging sprouts. However, Singh and Agarwal (1981) propounded the nutritional theory for a succession of ratoons. The presence of adequate quantities of both major and minor elements in stubbles and subsequent availability to ratoon shoots would possibly decide the ratooning power of cane cultivars.
The inheritance of ratooning ability in sugarcane was studied by Milligan et al. (1995). Ratooning Ability (RA) was defined as second crop yield (SR) per cent of plant cane yield. Stalk number in younger crop was the only trait correlated with the ratoon cane yield. Hence, selection for stalk number in young crop is suggested to improve ratoon yield. However, Sundara (1989) suggested that a high stalk number, bud viability, vigorous root formation, and high biomass are indicative of good ratooning power of cane cultivars. Maintaining stalk weight in older crops has been noted by Chapman (1988) as an important parameter. Invariably varieties with high plant cane yields produce high ratoon yields.
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Sugarcane in agriculture and industry
1 3 . 1 2
WATER REQUIREMENT
Ratoons are more prone to moisture stress than the plant crop. It is therefore,
recommended that the plant crop be irrigated at 50% Available Soil Moisture
(ASM), compared to ratoons at 75% ASM in sandy loams and medium black
soils. Workers in Australia found that ratoons can be irrigated at a pan ratio of
0.85. It was observed in sandy loam soils (Hunsigi, 1989) that when ratoons were
irrigated at 74 mm Cumulative Pan Evaporation (CPE, 14-15 days) in conjunc
tion with use of trash mulch 3 t ha -1, yields were on par with those obtained when
frequent irrigations at 19 mm CPE (4 days interval) were used. Table 13.17 sug
gests that ratoons responded more to drip irrigation than to subsurface irrigation
(Shih, 1989). Shih (op. cit.) observed a linear relation between yield and ET. Similar correla
tion was observed in Pelwatte Sugar Co. Ltd., Sri Lanka (pers. commn. S. P Jaiswal). But at any ET value, yields are lower in ratoons than in plant crop as shown by the regression lines for the plant cane and first ratoon.
Plant cane yield = 61.7 + 0.327 ET (r = 0.89, n = 11)
1st ratoon yield = -24.5 + 0.0653 ET (r = 0.82 n = 11)
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13 Managing the ratoon cane
The linear regression lines between yield and ET are depicted in Fig. 13.7. In Bacita Sugar Estate, Nigeria, reference evapotranspiration (ET ) was calcu
lated by the modified Penman method (pers. commn. S. P. Jaiswal). The maximum evapotranspiration (Etm) is given by the relation
Etm = K .ET c o
The crop coefficient Kc increases from a minimum value of 0.4 at emergence to a maximum of 1.15 during grand growth phase and declines to 0.6 at maturity. Based on this equation, the ET varied from a low of 2.4 mm d_1 to a maximum of 7.9 mm d-1. Thus the total ET for the plant or ratoon crop ranged from 1719 mm to 1804 mm under Bacita conditions (pers. commn. S. P. Jaiswal). However, these figures are very high. Soopramanien (pers. commn.) indicated that the ET of cane ranges from 1267 mm in South Africa to 1522 mm in Australia. Water Use Efficiency (WUE) also declines with older ratoons. In well-drained soils, not only are more number of ratoons taken but ratoon yields are also quite satisfactory.
Fig. 13 .7 Relation between yield and ET of plant ratoon cane, Pelwatte Sugar Co, Sri Lanka
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Sugarcane in agriculture and industry
WUE was 1 • 18 t h a - 1 cm -1 for drip irrigation compared to 0.67t ha-1 cm-1 for furrow irrigation. A m o n g the surface irrigation methods, alternate furrow irriga-
tion is super ior to n o r m a l practice. But double row planting with a skipped area or 120 cm a n d m u l c h e d with 3 t ha -1 trash gave the highest cane yield. Lowest ET was observed in sk ip furrow irrigation, (Hunsigi and Shankaraiah, 1982).
13.1 3
GAP FILLING
nis is an i m p o r t a n t operation for successful ratooning in sugarcane. Almost witho u t except ion, l o w r a toon yields can be attributed to gaps or stubble death. Nearly 2 5 - 3 0 % of t he a rea needs to be gap filled. Poor ratoons in Taiwan are attributed to t he failure of b u d s to germinate due to the presence of nymphs of Mogannia hebes w h i c h poss ib ly produce a toxin called bud germination inhibitor. Recent evidence indica tes t h e allelopathic effect of old stubbles. Research by Prasad et al. ( 1 9 8 1 ) reveals t h a t m o r e than 20% gaps results in considerable yield loss (Table 13 .18) .
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13 Managing the ratoon cane
It is worth replanting if gaps exceed 50%. For the establishment of filled-in-gaps, super-saturated soil moisture condition and high ambient humidity is desirable. For surer establishment, pre-germinated buds are recommended. The transplanting of seedlings raised in polybags are the best choice. Seedlings are raised in polyethylene bags of 10 x 15 cm filled with soil, sand and FYM in equal proportions. 4-6 weeks old transplants are used for gap filling. If a single bud is used, horizontal planting is better than vertical planting.
Under adverse climatic conditions like low temperature and frost as in subtropical India, sprouting is encouraged by transparent polyethylene mulching. This resulted in increased shoot and stalk population with consequent increased yield. Polyethylene mulching effectively controls weeds. Liquid mulch is suggested as it is cost-effective with improved yield and quality.
1 3 . 1 4
TRASH MANAGEMENT
The nutrient value of trash is negligible (Ng Kee Kwang et al., 1987). But its distinct utility in conserving soil moisture is well appreciated. Hunsigi (1999) reiterated that ratooned cane is ideally suited to organic farming since 7% total biomass is left in the field in the form of stubbles, roots, etc. The earlier practice of burning trash is nothing short of a disaster; trash needs to be conserved in situ. Trash is raked and spread uniformly between the cane rows. Cowdung slurry and urine or press mud are sprinkled for early decomposition. Trash can also be decomposed by employing microbes such as Trichoderma Viridae. Trash associated N2 fixation in combination with cellulytic bacteria could be the strategy in the future to achieve sustained ratoon cane production. Trash also acts as a mulch to conserve soil moisture and control the weeds. Recent research amply demonstrates that weed control is also achieved due to the production of allelochemicals from mulched trash.
In the cane rows trash is allowed to decompose either by the addition of press mud/cow dung slurry/cellulytic microbes. This decomposition is allowed for 4—6 weeks. After the incubation period, N2 fixers like Azotobacter/Azospiriltum are added at 5 kg ha-1 to the cane rows. Azospirillum, being microaerophyllic, is more suited than Azotobacter in the compacted ratoon cane soils.
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At this stage P-Solubilizing Microbes (PSM) and enriched press mud are mixed in the soil and final earthing up is done by 2½-3 months.
1 3 . 1 5
MANAGEMENT OF WEEDS, PESTS, AND DISEASES ASSOCIATED WITH RATOONS
The weeds which persist in ratoons are Cynodon dactylon, Panicum repens, Imperata cylindrica, Ipomea hardwichii, Cyperus rotundus, Sorghum halepense, etc. Ratoons require an early weed-free environment (60—75 days) before the 'rapid-close-in' period. Pre-emergence sprays of Atrazine/Diuron at 2.5 kg ha-1 effectively manage the weeds.
Diseases associated with the ratoons are: smut, grassy shoot (GSD), ratoon stunting (RSD), red leaf spot, and ratoon chlorosis, Diseases like smut, RSD, and GSD are fairly controlled by heat therapy. Pests specific to ratoons are shoot, root and top borers, pyriila, black bugs, white fly, scale insects, and mealy bugs; their control measures are detailed elsewhere in this book.
1 3 . 1 6
EFFECT OF GROWTH REGULANTS ON SPROUTING AND RATOON YIELD
Sugarcane has four types of growth regulants namely auxins, gibberellins, cytokinins, and growth inhibitors. Literature is replete with their role in plant/ ratoon cane and Hallman (1990) has presented a comprehensive review of these regulants. Kanwar and Kaur (1977) have shown that spraying of mercurial compounds like emisan/agallol to stubbles improved sprouting, stalk density, and yield. This is attributed to their hormonal influence besides their controlling of sett borne diseases. Growth regulants such as gibbereilic acid (GA3), indole acetic acid (IAA), indole butyric acid (IBA), triode benzoic acid (TIBA), Ethrel (2, chloro-ethyl phosphonic acid), and chlorocholine chloride (CCC) have improved early sprouting and the sprouts are converted to millable canes; hence there is increased yield. Quality remained unaffected due to these growth regulators. A recommendation is to spray CCC to stubbles at 8-10 kg ha-1 to improve ratoon sprouts and yield. Growth regulants can be mixed with pre-emergence herbicides and sprayed onto stubbles.
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13 Managing the ratoon cane
239
Sugarcane in agriculture and industry
Further, these growth regulators help to fight abiotic stresses like frost and drought. A detailed investigation by Bhale and Hunsigi (1994) showed that ethrel 500 ppm or CCC at 2000 ppm significantly improved sprouting. These are also instrumental in increasing millable cane population, length and girth of cane with a consequent increased yield (Table 13.19). Root pruning was equally effective as a low cash input in increasing the ratoon yield. Recently Mathan (1998) demonstrated that granular application of cytozyme at 15 kg ha-1 at 45 DAR (Days After Ratooning) followed by a supplemental dose of 12 kg ha-1 at 75 DAR resulted in higher cane yield in plant and ratoon crops of Co 86010.
Increased yield is attributed to increase in plant density at harvest, weight and girth of cane. Two sprays of cytozyme each 0.1% at 45 and 75 DAR are equally effective. Cytozyme is a biologically derived product containing protein extract enriched with micronutrients, GA3, and cytokinin. Other growth regulators such as Phytotron and Agrispon have affected positively the LA, LAI, LAD, and partitioning.
1 3 . 1 7
ALLELOPATHY IN RATOON CROPPING
Allelopathy is derived from two Greek terms meaning mutual harm. This term was first introduced by Molisch in 1937 and refers to biochemical interactions among plants including those mediated by microorganisms. Rice (1984) defines allelopathy as "the direct and indirect, harmful or beneficial effects of one plant on another through the production of chemical compounds that escape into the environment and generally into the rhizosphere". But allelopathy is divorced from resource competition. Autotoxicity and heterotoxicity are two types of allelopathy. Further, secondary plant metabolites and their degradation products are important in allelopathic effects in all agro-ecosystems. Allelopathy results when living organisms produce bioactive molecules which in turn may be modified. These compounds enter the environment and produce direct or indirect effects on the growth and development of plants.
Several phytotoxic substances produced from plant tissues and soils are suspected to inhibit germination and growth. These substances are called allelochemicals, and are secondary plant products or waste products of the main metabolic pathway in plants. These may be water soluble, and are released directly
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13 Managing the ratoon cane
from living plants into the environment through leaching, root exudation and volatalization, and decomposition of plant residues. The diversity of allelochemicals produced by plants is vast and chemicals range in structure from simple hydrocarbons to complex polycyclic aromatics. Almost every class of secondary metabolites has been implicated in allelopathic interactions. Rice (1984) has classified these allelochemicals in 5 categories, namely, phenyl propenes, acetogenins, terpenoids, steroids, and alkaloids. Some important allelochemicals are quinones, tannins, gallic acids, polypeptides, coumarins, flavonoids (condensed tannins), terpenoids, and steroids.
Most of the allelopathic affects were studied in mulch/crop residue on plants. Trash management is an important component of ratoon cropping. But trash mulch can serve as allelopathic mulch and provides weed suppression through physical presence on soil surface and release of allelochemicals or microbially altered products. These chemicals inhibit the germination of many weed species. Miller (1996) indicated that saponins have the potential of herbicides. Thus the use of cover crops or trash in cane may augment weed control methods to complement conservation tillage in crop production.
Understanding allelopathy may hold the key to a new weed management strategy. Weston (1996) emphasized that it offers potential for biorational weed control through production and release of allelochemicals from roots and decomposing material. He observed that under appropriate conditions allelochemicals may be released in adequate quantities to suppress weed seedlings. More often than not, they exhibit selectivity like synthetic herbicides. Biorational weed control through allelochemicals ensures environmental preservation, which is of utmost public concern. The phytotoxicity is a function of both concentration and flux rates in soil and rhizosphere.
In general, soil sickness under monocropping is due to allelopathy since many toxins are added. But tillage alters the toxic levels. In continuous cropping as in sugarcane ratoons, gaps are likely to be due to allelopathy. Verma (1995) concludes diat the number of ratoons in sugarcane is restricted due to toxic substances in the rhizosphere from fungi like Fusarium oxysporium, and Tricho derma harzianum. The success of a large number of ratoons depends to a large degree on co-adaptation and co-evolution to detoxify the range of allelochemicals. Future work must address these problems in a more directed manner.
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1 3 . 1 8
ENVIRONMENTAL CONCERN: A PLEA FOR INTEGRATED NUTRIENT MANAGEMENT (INM)
Sugarcane is not only heavily fertilized but heavy machinery is also used for harvesting and cane haulage. It is obvious that soils become compacted leading to erosion losses. Conway and Pretty (1988) have discussed fertiliser risks in polluting the surface and ground water in developed and developing countries. As quoted by them, the regional averages are 30 kg N ha-1 for Asia, 15 kg N ha-1 for Latin America and 4 kg N ha-1 for Africa, compared with the averages of 188 kg for Western Europe and 146 kg for Japan. Nitrates and the phosphates are the chemicals involved in pollution with the former subject to leaching and the latter being lost through soil erosion. Adiscott and his associates (1990) demonstrate that the surplus nitrate curve can be expected when N fertilization is beyond the point of saturation (Fig. 13.8). Such NO3 finds the way to ground water, thence to lakes, streams and rivers. Nitrate consumption can lead to the 'blue baby syndrome' or mathamoglobinaemia. Hence World Health Organization (WHO) and United States Public Health Service have placed a safe limit of 45 mg nitrate 1-1 in drinking water. Chemical fertilization cannot be totally dispensed with. Even in the best organic farming system, nearly 20—25% reduction in yield can be anticipated. Reduced yield of cane/sugar cannot be the goal of the developing countries of Asia, Africa and Latin America. Hence Integrated Nutrient Management (INM), a happy blend of bulky manure and chemical fertilizers is practical.
Non-symbiotic N-fixing bacteria such as Azotobacter and Azospirillum can add 30-75 kg N ha-1 to sugarcane fields. Based on many experiments, Srinivasan (1989) has categorised cane varieties with respect to their responsiveness to biofertilizers. P-solubilising bacteria like phosphobacterins in conjunction with rock phosphate need to be used extensively in ratoon culture. Industrial wastes such as filter press mud should increasingly be used, which greatly aid in organic matter build-up. Time-tested green manuring should be a part of cane culture. Intercropped legumes and crop residues like stubble, trash etc. should be incorporated into the soil after cane harvest. Experiments have amply demonstrated that N responses are nearly doubled in the presence of crop residue resulting in a saving of 50-100 kg N ha-1.
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13 Managing the ratoon cane
Fig. 1 3 . 8 Surplus N 0 3 - N curve (Addiscott et al., 1990)
To wrap up, Hunsigi (1999) has emphasised the organic way of growing ra
toon cane. To achieve successful organic ratoon cane, synchrony between the plant
demand and nutrient supply is highly essential. High degree of synchrony is pos
sible in a long duration crop like sugarcane with expansive root system, multiple
cuts, mixed cropping and high plant densities. But in sugarcane, recalcitrant ma
terial such as ligno celluloses, hemicellulose and polyphenols enter the organic
pool. Hence nutrient release is restricted/limited. It becomes essential to add high
quality litter to fasten plant decomposition. 10 t ha -1 press mud or cow dung
slurry is added to trash. This assures Soil Organic Matter build-up (SOM). In
tropics the soils should be mulched to reduce decomposition of SOM. As a thumb
rule, 5% SOM and a minimum of 30% replacement of inorganic fertilizers lead
to sustainable production. This also provides soil resilience so that the soil comes
back to its original condition. A consortium of microbes involving cellulytic bac
teria (Trichoderma viride), trash associated N2 fixers and P-soiubilizers could be
the strategy in the future to achieve organic farming and sustainable crop produc
tion.
243
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Plate 13 .2 Emisan
244
Plate 13.1 GA
13 Managing the ratoon cane
Plate 13.3 ETH (Ethrel)
Plate 13.4 Control
245
Sugarcane in agriculture and industry
Pla te 1 3 . 6 Trash + compost
246
Plate 13.5 Cycocel(CCC)
13 Managing the ratoon cane
-nit
P l a t e 1 3 . 7 Trash burning in situ
P i a t e 1 3 . 8 Trash + cow dung
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Sugarcane in agriculture and industry
Pla te 1 3 . 9 Trash + press mud
248
Management of seed cane
The seeds obtained from fluff are not used for commercial cultivation but they are used for breeding. Sugarcane is vegetatively propagated and in commercial parlance, seeds are cane pieces with 2 or 3 eye buds, called setts. Three eye buds setts are commonly used, but two eye bud setts are preferred.
A good seed in sugarcane is defined as the sett obtained from a healthy 8-month-old crop. It should be free from pests and diseases. A quality seed or sett is one which has (a) high tissue moisture (b) reduced sugar content and (c) soluble nitrogenous compounds. The sett should be fresh and each node should have a healthy bud. The seed pieces should not have adventitious roots, or splits and must be free from mixtures.
Farmers have a tendency to use the 1/3 top portion of non-flowered cane for seed purposes, and the rest is sent to the factory for crushing. This is a contingency plan and need not be a routine practice. The seed material from the ratoon crop should never be used. In Java, Indonesia, a short crop (seed nursery) is raised. It is a well-tended crop with adequate watering and manuring. The seed crop is harvested after six months and this is folowed by another cut after six months. In a normal seed crop the ratio is 1 : 10, i.e. 1 ha of seed would suffice for 10 ha. But in a short crop, the seed multiplication rate can be as high as 25 to 100 times.
In India, the seed is prepared manually. Trash and green leaves are scraped by a sickle without damaging the buds. If buds are prominent, self-detrashing cultivars are preferred. However, extreme caution needs to be exercised while preparing the seed material. Extensive damage takes place during transportation. It is always preferable to use the seed material within the local area. If transporting of the seed becomes inevitable, the entire cane with the trash and leaves is carried to the field, and manual cutting is done in the plot intended for planting. Seed cutting machines are also available, which cut 12000 setts per hour. But wastage is to the extent of 25%. Fresh setts should be used for planting. But if there is a delay in planting for various reasons, the whole cane or setts are kept in shade covered with trash or straw. Occasional sprinkling of water is beneficial. Cowdung slurry or a 1% urea solution spray on the heap of setts is quite useful.
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14 .1
SETT TREATMENT
There are a number of sett-borne diseases like pineapple disease which cause loss in germination. Setts are treated with organomercurial compounds like Agallol/ Areton at 0.1%. Bavistin, a systemic fungicide is now recommended at the rate of 1 gram per litre of water. Bavistin at the rate of 100 g is dissolved in 1000 litres of water for planting one hectare. The setts should be dipped in this solution for 5 minutes. This ensures good germination and vigour of seedlings. Fungicidal treatment of Bayleton at 0.1% for about 5-10 minutes is equally effective in controlling sett-borne infection of setts. Setts may be dipped for 10 minutes in 0.1% Carbendazim.
1 4 . 2
AGRONOMY OF SEED CANE
The work in this aspect is sketchy. However, a wider spacing of 90—100 cm is desired for inspection and roguing of the affected clumps. At the primary stage about 25% higher seed rate is required due to germination loss following heat treatment. The important seed borne diseases are Ratoon Stunting Disease (RSD), Grass Shoot Disease (GSD), and smut. They cause a progressive loss in yield and quality, and are also probably responsible for the varietal decline. Seed plots are well-manured with 25 tons FYM per ha. Recommended dosage of fertilizer and the number of times the fertiliser should be applied:
The recommended dosage is N —250-300 kg; P2O5—75-100 kg, K2O— 125-150 kg per ha.
The fertilizers may be given in 3 splits. Basal: Full phosphorus applied in the bottom of the furrow. At 30 days: 1/3 N + 1/3 K applied as band placement, close to the rows and
light earthing up. At 60 days: 1/3 N + 1/3 K applied in bands and slightly earthing up. At 90 days: 1/3 N + 1/3 K applied at the base followed by final heavy earthing up. About 25% additional N and P, and about 30% extra K (tentative) are given 6-
8 weeks prior to harvest. Humbert (1968) suggests this as pre-fertilizing the crop.
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14 Management of seed cane
251
The prefertilized setts germinate rapidly with vigorous seedlings and a high proportion of roots and shoots. Normal intercultivations and earthing up are done. But the seed crop is harvested at the 8-month stage. For early maturing and short duration varieties, it is harvested even at the 6-7 month stage.
It is ideal to irrigate the crop at 25% Available Soil Moisture (ASM) or IW/CPE ratio of 1.0. This works out to 6—7 days interval in lighter soils and 10-12 days in heavier clay soils. There should be no water stagnation. Weed-free environment can be achieved by pre-emergence application of atrazine at 1.75 kg ai ha-1
(3.75 kg ha-1 of the commercial product). The normal multiplication rate is 1 : 10 but this can be increased by single bud
direct planting or Spaced Transplanting Technique (STP). With these methods the multiplication rate is 1 : 15 or even 1 : 20. It is also advisable to raise the primary seed nursery in polythene bags or plastic cups. About 4—6 week old seedlings are transplanted. Before transplanting, the leaves must be clipped to reduce the transpiration loss.
The following precautions should be taken while managing the seed nursery. (a) Problematic soils such as saline/alkali soils should be avoided. (b) Adequate irrigation facility should be provided. (c) The seed nurseries should be distributed in different sections of the factory
reserve area for distribution. (d) Primary nurseries should be raised by the factory farm/research stations/
Government seed farm. (e) While preparing setts, knives must be dipped for about 5 minutes in 0.1%
solution of Agallol/Areton/Bavistin. (f) Sharp knives should be used to cut the seed material, while placing the
dressed cane on a log of wood.
1 4 . 3
THERMOTHERAPY OR HEAT THERAPY
It is an age-old practice and is very effective against seed-borne diseases like GSD, RSD and smut. The basic principle is that pathogens present in seed material are inactivated or eliminated at temperatures not lethal for the host tissues. Hot air treatment was advocated for 8 hours at 58 °C. But this caused drying of setts with
Sugarcane in agriculture and industry
a serious loss in germination. It had to be dispensed with. Three types of heat
treatments are used for administering thermotherapy to sugarcane setts, i.e.
(a) Moist Hot Air Treatment (MHAT) at 54 °C ± 1 for 4 hours.
(b) Hot Water Treatment (HWT) at 50 °C ± 1 for 2 hours.
(c) Aerated Steam Therapy (AST) at 50 °C ± 1 for 1 hour.
In H W T , setts are placed first in preconditioning tanks with water at 40—45 °C
before treating at 50 °C to avoid shock.
Any one of the types may be used. There are no escapes (Despite heat therapy,
some setts show disease symptoms upon germination, hence the term escapes.).
The primary seed nursery is administered with thermotherapy and strict roguing
of affected clumps must be observed at all stages. General hygiene must be strictly
followed, and the primary seed nursery in the factory/Government farm must be
supervised by a technical person.
1 4 . 4
THREE-TIER SEED PROGRAMME
The three stages of seed multiplication are: the first stage—Foundation seed or
primary seed, second stage—certified seed and third stage—commercial seed. Al
exander (1995) has presented a heat treated nursery programme utilising AST to
cover 10,000 ha area of the factory (Fig 14.1). The factory area of 10,000 ha is
divided into 5 sectors of 2000 ha each. In the first year, 20 ha in sector I is planted
with AST treated setts. In the second year, the cane in the 20 ha area in Sector I is
multiplied to 200 ha (10 times), and simultaneously 20 ha in sector II is planted
with AST treated setts.
In the third year, cane in the 200 ha area in sector I is multiplied to 2000 ha, thus
covering the entire sector. Cane in the 20 ha area in sector II is multiplied to 200 ha.
Simultaneously 20 ha in sector III is planted with AST treated setts (Fig. 14.1).
Thus the cycle is repeated covering the entire factory zone of 10,000 ha once in five
years. At each stage careful inspection and roguing is necessary. Under proper super
vision, the treated material needs to be changed once in five years.
Chemical treatment of the setts is done to protect the cut ends from invasion
of soil-borne diseases like pineapple disease, wilt, etc. Organomercurial compounds
at 0 .25% or Carbendazim at 0 . 1 % as a sett-dip for 10 minutes is recommended.
A combination of hot water treatment (50 °C ± 1 for 2 hours) and fungicidal
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14 Management of seed cane
treatment (Bayleton 0.1%) has been found to be effective in the control of the sett-borne infection of smut.
Fig. 14.1 A three-tier sugarcane seed nursery programme to cover 10,000 ha
253
Integrated weed management
Weeds—plants out of place—need to be effectively managed. They compete for
nutrients, moisture and light, besides serving as alternate hosts for many pests and
diseases. Bermuda grass (Cynadon dactylon) and Logon grass (Imperata cylindrica)
play alternate hosts to ratoon stunting disease. The losses caused by weeds is per
haps more than that caused by insect pests and diseases. Peng (1984) has reported
that 200 species of weeds infest sugarcane fields and 30 are of economic impor
tance. According to him the common families are Cyperaceae (35%), Umbelliferae
(30%) and Gramineae (18%). Some important weeds of sugarcane are listed in
Table 15.1. World over the yield loss in cane is approximated at 15% while in India the
losses range from 12 to 72%. In Taiwan, yield loss was 8-18% in cane and 9-39% in sugar (Peng, 1984). One estimate in India has shown a yield loss of 17.5 t ha -1 in the tropics, and 23.7 t ha -1 in the subtropics. Twining weeds like Ipomea hederaceae and /. hardwichii can cause yield losses up to 2 5 % to 30%. Besides, they are a hindrance to manual harvesting. Sugarcane is widely spaced and the initial growth is slow. Hence weed infestation is higher in the initial stages and they rob 40—42% of the nutrients. The critical stage for sugarcane is the initial 90-100 days before rapid-close-in, when a weed-free environment has to be provided to the crop.
Weeds not only compete for moisture, nutrients and light, but are also known to produce allelochemicals which reduce the yield of cane. Some weeds have al-lelopathic effect on other weeds. The decaying rhizomes of Sorghum halepense affect the growth of Setaria sp., Digitaria sp., and Amaranthus sp. The extracts of Sorghum halepense (Johnson grass) have shown that certain flavonoids are produced which are harmful to Digitaria sp. and Amaranthus sp. As a consequence, certain weed populations dominate the others.
The weeds serve as alternate or collateral hosts for many pests. Sorghum halepense serves as an alternate host, and its removal reduces the infestation of stalk borers.
Some weeds are parasites on sugarcane. The weed Aeginetia indica (Bunga) belonging to the family Orobanchaceae (Broom-rape family) is a sugarcane root parasite. The roodess and chlorophyll-less flowering plant absorbs water and nutrients from sugarcane roots through its haustoria. This parasitic weed produces enzymes which reduce sucrose to glucose and other reducing sugars.
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15 Integrated weed management
Table 15 .1 Some important weeds in sugarcane fields
Source: Peng, 1984.
Growing a resistant variety like N C O 310 is a sure answer to this parasitic
weed. Another root parasitic weed is Striga sp. which is common in black soil
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Sugarcane in agriculture and industry
when cane is grown in rotation with sorghum. Like all other root parasites, it produces haustoria to absorb water and nutrients from sugarcane roots. Deep ploughing and digging control this weed. Trap crops like gingelly, flax, coriander, cowpea, sesamum, blackgram and greengram help to control his weed. Rotation with cotton and pulses reduces the striga population. The chemical control includes foliar application of amine salt of 2, 4-D at 1.0 1 ha¬1 in 900 1 of water or soil incorporation of Fenac (Chlorofenac, 2, 3, 6 TBA) at 3 kg ha - 1 in 700 1 of water.
In cane fields, monocots and dicots together with Cyperus sp. are present to form a balanced weed population. In sandy, sandy loam, loam, and clayey soils broad-leaved weeds, grasses, and Cyperus sp. each 30%, and the remaining 10% hard-to-control-rhizometous-perennials constitute the weed population. Over the years spraying of one group of herbicides has lead to the control of dicots but the dominance of perennial grasses has also increased. This shift in weed flora in favour of grasses can be arrested by a combination of 2—3 groups of herbicides to maintain a balanced weed population. Hence herbicide mixtures or 'cocktails' are preferred to prevent the build-up of resistant species.
15.1
INTEGRATED WEED CONTROL
This includes
(a) Mechanical (interculture, handweeding, digging, etc.) methods
(b) Biological suppression of weeds by intercrop competition (c) Biological methods
(d) Chemical methods
(e) Genetically modified Herbicide Tolerant (GmHT) crop plants which result in weed reduction.
No single method is comprehensively effective, hence all combinations are employed to manage the weeds. Burning of trash to control pests, diseases, and weeds needs to be discouraged. But mulching at 5-8 t ha -3 suppresses the weed growth. Proper rotation and intercropping keep the weeds at bay. Rotation with pulses, cotton, and oilseed crops minimises the weed infestation. The smother crops like cowpea, beans, potato and sunn hemp as intercrops substantially reduce the weeds in sugarcane.
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15 Integrated weed management
Bioherbicides is a new concept where plant pathogenic organisms such as fungi, bacteria, viruses are used as biocontrol agents. These bioherbicides are applied in a manner which is similar to chemical herbicide application. A few mycoherbicides (fungal pathogens) have been used to control weeds in soyabean, cotton, and rice. Biological control is worth mentioning. The larvae of Bactra verutana (moth) have been found to bore into the shoots of Cyperus rotandus. Geese are efficient biological agents to control weeds in sugarcane.
Genetically modified Herbicide Tolerant (GmTH) plants are a recent introduction. Almost a decade ago, the first transgenic herbicide tolerant plant to be produced was the transgenic tobacco plant tolerant to glyphosate. This is done by transforming tobacco leaf discs with an agrobacterium strain carrying a glyphosate tolerant enzyme. Gallo-Meagher and Irvine (1996) have introduced the bar gene to sugarcane for herbicidal resistance to Ignite (glufosinate ammonium). Engineering resistance to herbicide can be achieved by over-expression of the target enzyme.
The mechanical methods of weed control include flaming, flooding, deep tillage, discing, blind tillage, hoeing, and harrowing. Mulching with trash at 5-8 t ha-1
controls the weeds. Mulching with opaque polyethylene (PE) has been tested with success. After mulching, emerged weeds remain inside PE, become etiolated and die. Intercropped green manure crops like sunn hemp and Sesbania sesban can control weeds through smothering effect.
Chemical control in conjunction with other methods is quite effective in providing a weed-free environment for sugarcane in the first 100—120 days. The chemical herbicides are classified into three groups depending on the type of treatment and their mode of action. (a) Contact herbicides. These are applied to the foliage but do not move far
from the site of action. They kill the tissues which come in contact. (b) Translocative herbicides. These are applied to the foliage and can move from
the site of application to the other parts of the plant . Their action is systemic and they move with the metabolites in the phloem tissue.
(c) Residual herbicides. These are applied to the soil and are absorbed by roots. They are more persistent and move mainly in the xylem through the transpiration stream.
Some examples of contact, translocative, and residual herbicides used in cane plantations are presented in Table 15.2 and the mode of action is depicted in Figure 15.1.
257
258
Fig. 15.1 The movements of the two types of herbicides through leaves or roots of the plant after their application on either foliage or soil surface (Peng, 1984)
The most commonly used herbicides in cane culture are: asulam, atrazine, metrabuzin, diuron, cyanazin, ametryne, trifluralin, alachlor, metalochlor, pendimethalin, hexazinone, paraquat and phenoxy acetic acid compounds. It is generalised that herbicides like atrazine, diuron 2, 4-D applied at 2 to 2.5 kg ha-1
as pre-emergence spray are effective and economical. But metrabuzin (70%) at 1.0 kg ha-1 has qualified as an excellent grass killer. Glyphosate at 1.0 kg ha-1 as early post-emergence spray is equally effective. This author has found that uracil at 1.5 kg ha -1 as pre-emergence spray effectively controlled weeds in sugarcane. In ratoons 1.0 to 1.5 ai ha-1 of atrazine was effective and economical as pre-emergence spray. The standard application is diuron + 2, 4-D or Atrazine + 2, 4-D each at 1.6 + 1.6 kg ai ha-1 as pre-and post-emergence spray. Atrazine controls
Sugarcane in agriculture and industry
15 Integrated weed management
Table 15 .2 Different types of herbicides
most of the dicots and grasses but not vegetatively propagated weeds like Cynadon and Cyperus. In areas where monocots are dominating, metrabuzin (Sencor) at 1.0 to 1.5 kg ha-1 is effective. Metrabuzin at 1.0 kg ha-1 as pre-emergence spray and 2 kg ha-1 of 2, 4-D as post-emergence spray was found suitable in many cane growing areas. If a sensitive weed flora like Philaris minor is dominant, isoproturon
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(1 to 1.5 kg ha -1) can be used. For Cyperus, paraquat, a contact herbicide can be used at 0.75 to 1.0 kg ha - 1 when cane reaches the 6-leaf stage or 3 weeks after the emergence of Cyperus. This is a directed, post-emergent application. Isouron has been found to be very effective in controlling Cyperus, but it has phytotoxicity with reduced tillers and yield. Under saline conditions, 2.5 kg ha - 1 asulam + 2, 4-D sodium salt at 1.6 kg ha -1 as pre-emergence spray is effective in weed control.
A list of herbicides, commercial names and their dosage used in sugar industry is given in Table 15.3.
In Mauritius, the common herbicides used in sugar plantations are atrazine, diuron, acetochlor, metolachlor, and oxyfluorfen as pre-emergence spray. The rates of application range from 1 to 4 kg ai ha - 1 . High rates of application may lead to environmental pollution. Mclntyre and Barbe (1995) observed that in Mauritius the regular practice was the pre-emergence application of diuron + Actril-DS (2.5 + 1.3 kg ai ha - 1) or diuran at 4.0 kg ai ha - 1 . These treatments have less residual effect and the mixture of diuron + actril is phytotoxic. According to Mclntyre and Barbe (1995), the objective was to screen newer herbicides with longer residual action and safer post-emergent herbicides for young plants and ratoon cane. The results indicated that oxyfluorfen alone at 1.0 kg ai ha - 1 or a mixture of oxyfluorfen + diuron (0.5 + 2.0 kg ai ha - 1) were the best herbicides and controlled weeds up to 6 months until the leaf canopy was formed. Acetochlor + atrazine (2.0 + 2.0 kg ai ha -1) or metazachlor + atrazine (0.75 + 2.0 kg ai ha - 1) were safe as post-emergence sprays in plant crop and regenerating ratoon cane. Various trials showed good potential for new herbicides—oxyfluorfen, acetochlor, and metazachlor for general weed control. Both acetochlor and metazachlor were more effective against Kyllinga bulbose and Oxalis sp. (op. cit.).
Seeruttun and coworkers (1999) have tried thiazopyr as a potential pre-emer-gent herbicide for sugarcane. Thiazopyr (trade name 'visor') is a pyridine herbicide and is considered to be ecofriendly. Atrazine or diuron at 2.0 kg ai ha - 1 when tank-mixed with thiazopyr and used as pre-emergence spray provides good control of weeds for sugarcane for at least 12 weeks. This combination is superior to acetochlor + atrazine, or diuron, at 2.3 + 2.0 kg ai ha - 1 . Thiazopyr controlled grasses such as Digitaria horizontalis, D. timorensis and Panicum subalbidum. Seeruttun et al. (loc. cit.) maintained that thiazopyr is a good alternative to acetochlor as it controls Panicum subalbidum.
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15 Integrated weed management
Adding thiazopyr to atrazine or diuron at 2.0 kg ai ha-1 improved the spec
trum of weed control. Moreover, this has no adverse effect on cane. It is interest
ing to note that the use of oxyfluorfen after planting and trash blanketing in sub-
humid areas have effectively decreased the use of herbicides (op. cit.) confirming
the findings of Mclntyre and Barbe (1995).
An attempt has been made in the Caribbean countries to use lower doses of
herbicides so as to reduce their adverse environmental impact. In the English
speaking Caribbean territories, chemical weed control in sugarcane relies on the
use of pre-and post-emergence treatments of atrazine, ametryne, diuron, and 2, 4-
D in various tank mixes. The post-emergence herbicides include terbutryne (early
stages), asulam or, occasionally, paraquat or glyphosate at later stages. Dasrat et al.
(1999) have observed that Isoxaflutole at 100—150 g ai ha - 1 can control grasses
and broad-leaved weeds. This herbicide has controlled noxious weeds like Rottboellia
sp. Panicum maximum, Echinochba colonum, Cleome ciliate, Croton trinitatis, etc.
[Isoxaflutole {Isoxaflutole = (5, Cycloprapyl-4—isoxazolyl) [2-methylsulfonyl)-
4-(trifluoromethyl) phenyl] methanone} acts by disrupting carotenoid biosyn
thesis, and is selective in maize and sugarcane.] Its efficacy improved when it was
mixed with diuron or atrazine. It is conjectured that Isoxaflutole acts as an adju
vant, and has an additive or synergestic effect in controlling the weeds. Yields
were not affected adversely by Isoxaflutole in the range of 100—150 g ai ha - 1 .
Care should be taken so that the dosage is not too high since the residues will
find their way into water bodies. The dosage that causes 20% crop mortality
(ED 20) and that which achieves 80% weed control (ED 80) are to be consid
ered. The ratio of ED 20/ED 80 is called the Sensitivity Index (SI). A SI of 3.0
and above is preferred. To find out the commercial product from the activity
index (ai), the following formula is used.
Weight of chemical to be applied ai
Percentage of ai expressed in percentage
For example 1 kg ai of diuron is applied with 80% wp (wettable powder).
The commercial product, i.e. Karmex = 1.0/0.8 = 1.25 kg.
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15.2
HERBICIDE PROTECTANTS, ANTIDOTES OR SAFENERS, SURFACTANTS AND ADJUVANTS
A new development in herbicide usage is the use of protectants or antidotes. This protects the crop plant from possible damage by a herbicide. This means that it may be possible to use certain herbicides on crops that would normally be affected by the herbicide. Some of the protectants are:
(a) Napthopyranone derivative e.g. Naphthalic anhydride (NA) and phthalic anhydride (PH4).
(b) Chloracetamide e.g. allidochlor (CDAA) and dichlormid (DCCA).
(c) Oxime ether e.g. cycometrinil, GCA 133205 and pyridine aldoxime ethers. Surfactant is coined from 'surface active agents' which include emulsifiers, de
tergents, and wetting agents (Peng, 1984). There are two major classes of surfactants, namely, the ionic and nonionic forms. Some of the emulsifiers belong to the nonionic group. The ionic surfactants are detergents, wetting agents, chemicals such as Citowett (alkylaryl polyglycolether) multifilm, Dalawet and even jaggery, molasses and common soap. The threshold concentration of surfactants is within a range of 0.1-1.0%. Surfactants have the following properties:
(a) Increase spray retention (b) Increase penetration of herbicide by increasing the contact area
(c) Act as solubilizing agents (d) Increase direct entry by lowering the surface tension of the spray solution.
Herbicide mixtures are commonly used in agriculture to broaden the spectrum of weeds that can be controlled (Peng, 1984). It is generalized that such mixtures have 'additive', 'synergestic or antagonistic' effects. There is mostly an enhancement of the effect in controlling weeds. Normally synergestic effect is seen when ureas and triazines are mixed with 2, 4-D sodium salt as pre-emergence application. A similar result was observed when asulam and 2, 4-D were mixed and sprayed as post-emergent spray. In this case, 2, 4-D appears to play the role of an adjuvant more than that of a herbicide (loc. cit.).
The compatibility of herbicides with fertilizers, insecticides and fungicides are seen within the recommended dosage. Most of these interactions are synergestic by controlling the pathogen and the weeds.
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1 5 . 3
WEED CONTROL IN CROP ROTATION AND INTERCROPPING SYSTEM
Crops that go in for rotation with sugarcane are rice, maize, potato, pigeon pea,
mustard and wheat. The common intercrops are wheat, potato, mustard, corian
der, garlic, onion, peas, beans, soyabean, and groundnut. Herbicides such as atra
zine, ametryne, metribuzin, and asulam which are the common soil herbicides for
cane are not suitable for intercropping systems. But in rotation, these herbicides,
up to 3—5 kg ha -1 as pre-or early post-emergence herbicides, have no effect on the
crops. Due to frequent intertillage and earthing-up operations, these herbicides
are detoxified in soil. Further, sugarcane has a long life cycle from 10—18 months,
and these herbicides are easily inactivated in soil.
For an intercropping system, herbicides which are more selective with lower
potency and shorter persistence are desirable. It has also been amply demonstrated
that intercrops like groundnut, cowpea, soyabean, french bean, etc. smother the
weeds and are effective in controlling weeds. For a sorghum + sugarcane inter
crop, cynazin at 1.0 kg ha - 1 + diuron 1.0 kg ha - 1 as pre-emergence spray was quite
effective. For grain legume intercrops like groundnut and soyabean, linuron at
1.5 kg ha - 1 or alacholor at the same dosage controlled the weeds satisfactorily.
The selectivity index (SI) of these herbicides was around 3.0. Similarly, amiben at
0.7 kg ha - 1 on furrows as pre-emergence spray was suitable for the common inter
crops like groundnut and soyabean in sugarcane. The weed control was to the
extent of 80% with no adverse effect on yield and quality of cane. The generally
recommended herbicides under intercropping system with pulses, oilseeds and
potato are alachlor/linuron. Studies at Coimbatore have shown that oxyfluorfen
(Goal) as pre-emergence spray at 0.3 kg ai ha - 1 is useful when pulses and oilseeds
are intercropped.
1 5 . 4
CONTROL OF NOXIOUS PERENNIAL WEEDS
Some weeds propagate through rhizomes and some are vegetatively propagated,
and they persist in the soil for several years. The weeds which are difficult to
control are: Panicum repens (Torpedo grass) Cyperus rotundus (purple nutsedge),
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C. esculentus (yellow-nut sedge) Cynodon dactylon (Bermuda grass), and Sorghum halepense (Johnson grass). Other prominent weeds are: Paspalum paniculatum, Panicum maximum, mimosa invisa, Imperata cylindrica, Paspalum conjugatum. These weeds persist in the soil for several years and are not easily controlled. The torpedo grass (Panicum repens) can be controlled by spraying a combination of dalapon + 2, 4-D (6 + 4 kg ai h a - 1 ) . For Bermuda grass (Cynadon dactylon) TCA can be used at 2-4 kg ha -1 in 4 5 0 0 1 of water. Directed foliar application of paraquat, dalapon, 2, 4-D at 2 + 8 + 2 kg ai ha -1 has controlled this weed for about 4 months. Nut sedge (Cyperus rottmdus, and C. esculentus) produces tubers and seeds. It can be controlled for 26 weeks by applying Glyphosate at 2, 4, 6 kg ha - 1 in three applications. The C o g o n grass, Imperata cylindrica, is one of the world's ten worst weeds. Glyphosate at 5—6 kg ha -1 has been tested and has been found to be effective. Dalapon at 5 kg h a - 1 , repeated 2—3 times can prevent regrowth. In cane p lan ta t ions , a m i x t u r e of paraquat + d iuron or paraquat + dalapon in 0.8 + 0.5 + 1.0 kg ai h a - 1 is quite effective. Johnson grass (Sorghum halepense) which produces bo th seeds and creeping rhizomes is widespread in Fiji, Australia, India, etc. Picloram at 1.7 kg ha -1 is effective as a pre-emergence spray but still it is difficult to control Johnson grass.
1 5 . 5
METHODS OF APPLICATION
For herbicides to be effective, care has to be exercised. The pre-emergence herbicide is applied within 3 days, and the post-emergence spray within 21 days. There must be sufficient m o i s t u r e in the soil and the land should not be cloddy. Spray drift should be avoided. It is preferable to spray the herbicides on a calm day in the evening hours. T h e selectivity and tolerance limit are conditioned by the soil type, variety, and m a n a g e m e n t practices. Cultivar N C O 310 is tolerant to diuron even at 20 kg ha - 1 . Similarly F 152 is tolerant to atrazine at high dosage. Varieties like Co 62175, Co 4 1 9 , Co 8371, and Co 86032 are relatively more tolerant to herbicide application t h a n Co C 671. Transplanted crops are susceptible to herbicides which have a residual effect. But ratoons have a fairly high tolerance to herbicides due to the de lay in the formation of shoot roots. Rayungans (pre-raised plantlets) are more suscept ible to soil application of herbicides. As reiterated ear
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lier, a mixture of herbicides is more effective in controlling a wider spectrum of
weed flora.
Generally, hand-operated knapsacks or backpack sprayers of 5—15 1 capacity
are used in India. Sprayers are fitted with different types of nozzles with varying
delivery rates. The droplet size is 400 microns. High volume sprays use
900-1000 1 ha - 1 of spray mixture and are useful for pre-emergence application of
herbicides. For power sprayers, the droplet size is 300 microns and the water
required is 200-300 1 ha -1 . For Ultra-Low-Volume sprayers (ULV) the droplet
size is 50—70 microns and the spray volume is 30-60 1 ha - 1 . ULV is useful for
systemic herbicides like glyphosphate, 2, 4-D, etc. Extreme precaution should be
taken while spraying if sensitive crops like cotton, pulses, etc. are grown in the
neighbouring plots. After use, the sprayers should be thoroughly cleaned.
To sum up, yield losses in sugarcane due to weeds range from about 10—20%
in cane, and 10 to 40% in sugar. No single method of control is effective. Hence
Integrated Weed Management (IWM), namely, mechanical, chemical, biological
suppression of weeds are suggested. The advantages of I W M are many:
(a) Shifts crop-weed competition in favour of crops
(b) Prevents weed shifts towards perennial nature
(c) Prevents resistance of weeds to herbicides
(d) Ensures environmental protection
(e) Gives higher net returns
(f) Suitable for high-cropping intensity
It is concluded with optimism that atrazine/diuron at 2—2.5 kg ha - 1 , or
metrabuzin at 1.0 to 1.5 kg ha - 1 is effective in controlling weeds in sugarcane.
Emphasis needs to be on trash blanketing, and on screening for low doses of
herbicides which are ecofriendly and protect the environment. Perennial grasses
and sedges are difficult to control but a weed-free environment has to be achieved
during the first 90—100 days. Surfactants and adjuvants have to be used to im
prove the efficiency of herbicides. When intercropped with sensitive crops like
pulses and oilseeds, low doses of herbicide have to be used with safeners or anti
dotes. Transgenic sugarcane with tolerance to major herbicide groups is conten
tious and needs to be watched carefully, lest the transgenic cane develops 'inva
siveness' or 'weediness'.
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Pest and disease management
Sugarcane is attacked by a large number of pests and diseases. Losses in yield and quality varies depending on the level of management and agro-ecological situation. Sugarcane stands in the field for 10-18 months and harbours a number of pests and diseases. T h e pest-disease menace is further accentuated due to continuous cropping as in racoons. Constant surveying and monitoring are essential to contain pests and diseases from spreading on a large scale to prevent heavy losses. Emphasis is now on Integrated Pest Management (IPM) and lntegrated Disease Management ( IDM) . This includes cultural, mechanical, biological, varietal, and chemical methods. T h e chemical control method should be 'need based' and is used when the level of pest/disease exceeds the threshold limit. Field sanitation is an important component of IPM and IDM.
16 .1
PESTS
David (1995) reports that sugarcane is ravaged by 212 insect pests and 76 non-insect pests. Yield losses could be to the extent of 20% depending on the level of infestation. The major pests of sugarcane are detailed in the following pages.
The major pests of sugarcane can be grouped into three categories.
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16.1.1 Shoot borer (Chilo infescatellus Snellen)
This is commonly known as early shoot borer and is widely distributed. Its menace is during the early phases of growth. The attack of the pest is accentuated under late-planted and moisture-stress conditions. The borer larva enters the cane killing the central leaf spindle and is easily diagnosed by the 'dead hearts'. The central leaf spindle can be easily pulled out and such plants have a tendency towards increased tillering. Hence Lakshmikanthan (1984) puts the threshold level at 30%. At the threshold level and above, the yield loss is approximated at 10-15 t ha -1. However, if the infestation is severe the yield loss could be much higher.
The control measures include cultural, mechanical, chemical, and biological methods. Light early earthing-up prevents the entry of the larvae. 'Dead hearts' are pulled out to kill the larvae. Late planting of cane is avoided and the crop is irrigated more frequently (7-10 days interval). Lindane (20% EC) is applied to the setts (Gamma H C H emulsion at 1.0 kg ai ha - 1 is applied over the sett at planting). Soil application of Sevidol at 12.5 kg ha - 1 around the base of the clump on the 30th and the 60th day after planting is advocated. This chemical can also be applied in whorls. Biological methods include spray application of the granulosis virus at 10 6-10 7 inclusion bodies per ml along with a surfactant like teepol or sandovit at 0.05% at the beginning of the pest infestation. If desired, the application may be repeated at fortnightly intervals.
16.1.2 Top borer (Scirpophaga excerpta/is walker)
It attacks at all stages of growth and is of economic importance in subtropical
India. The characteristic symptom is the 'bunchy top' due to the sprouting of the
top buds. The larvae bores through the central core and 'dead hearts' are found
which cannot be pulled out easily. Yield and quality loss could be to the extent of
20—30%. The control measures include collection and destruction of egg masses,
and roguing of the affected cane tops. Autumn planting is to be advocated.
Waterlogging should be avoided. Application of carbofuran 1.0 kg ai ha -1 or
phorate 3 kg ai ha - 1 during June-July for autumn planted cane controls the top
borer. Varieties like Co J 67, Co 1007, Co 1158, and CoS 767 may be employed
in the endemic areas. Biological control method includes release of Trichogramma
japonicum in the subtropics and Isotima javensis in the tropics.
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16.1.3 Internode borer (Chilo sacchatiphagus indicus,Kapur)
This is widespread both in the tropics and the subtropics, and infects when the internodes are formed. Lodged cane, water shoots, and canes in waterlogged conditions are severely affected. It normally attacks the top immature internodes. The larva tunnels upwards in a characteristic spiral fashion. Yield is reduced following the reduction in length and girth of the cane which are important yield components. The buds may not germinate with a consequent loss in yield and quality. Subsequent to borer injury, secondary infections of wilt and pine apple disease may occur.
The control measures include use of borer-free setts, detrashing at 5th, 7th, and 9th month of the crop stage, removal of water shoots, and avoiding heavy dose of N. Spraying 0 .1% monocrotophos reduces the initial borer population at the grand growth period (4-6 months). Biological control with Trichogramma chilonis released inundatively at 3.5 cc ha -1 at fortnightly intervals from the 4th month to harvest provides good protection against the internode borer.
16.1.4 Stalk borer (Chilo auricilius, Dudgeon)
This is a major pest in Uttar Pradesh, Haryana, Punjab, Bihar, and Orissa. At first, the larvae feed on the inner surface of sheaths, subsequently the sheath rots and the leaf dries out. The feeding of the leaf causes longitudinal orange-yellow streaks extending from the tip to the base. At a much later stage, the larvae bore into the internodes and the infected canes produce dead hearts, which is similar to what the early shoot borer does. The infected cane may dry up, and the damaged internodes may show reddening and emit rancid smell. Prolonged drought period, high N dose, frequent irrigation and waterlogged conditions favour the attack of the stalk borer.
The cultural methods to control the stalk borer are providing drainage and removal of water shoots. Control of Johnson grass (collateral host) will reduce the pest attack. Detrashing, destruction of water shoots, trash burning, etc. keep the stalk borer under check. Application of monocrotophos granules at 3 kg ai ha-1 in July is effective in controlling the pest. Under severe infestation, the yield loss is to the extent of 16-33%, and the sugar loss by 2 units.
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16.1.5 Gurudaspur borer (Acigona steniellus, Hampson)
This is the most serious pest of the subtropics. Its incidence was observed on an epic scale in Gurudaspur, Punjab—hence the name. Upon the entry into the internode, the larva feeds below the rind tissue in a spiral manner.
It makes minute punctures on the rind from within. Externally the tunnel appears as a dark spiral ring made up of a series of punctures looking like beads in a rosary. When the larvae feed below the rind, the leaves wither; later on the entire whorl dries up. Cane growth is restricted and breaks if slightly pulled. Side shooting occurs due to bud sprouting. Yield loss could be 10-20% but depends on the infestation. The control measures include use of borer-free setts, destruction of infested cane, burning of trash and stubbles, and avoiding ratooning of the highly infested crop. Soaking the setts in 0.2% trichlorophon for 2 hours before planting kills larvae present within the setts. Resistant/tolerant varieties like Co 11.48, CoJ 46, CoJ 64, Co 62175 should be used. Varieties with light sheath are less attacked. Inundative release of egg parasite Trichogramma chilonis at 1,25,000 parasites ha -1 checks the attack of this pest.
16.1.6 Root borer (Emmalocera depressella, Swinhoe)
This is the only borer which attacks the underground portion. The root borer is
widespread in the tropical belt, Northern Gujarat, Maharashtra, Karnataka, and
Andhra Pradesh. It attacks only the young shoots and causes 'dead hearts.' It rarely
attacks well-grown sugarcane. External symptoms are rarely seen except yellowing
of the leaves. Only on digging and on root exposure, the infestation can be seen.
The dead hearts cannot be easily pulled out like in the case of early shoot borer. The
loss in yield is about 10—15% and sucrose loss is 0.5-1.0 unit. T h e infestation of
root borer is high when the ambient temperatures are high with moderate humidity.
The attack is severe under unirrigated conditions and in light textured soils (sandy
to sandy loam). Ratoons are more prone to attack by root borer than the plant crop.
The mechanical methods of control include deep stubble shaving of ratoons,
removal and destruction of affected clumps, collection of moths by using light
traps, and digging and destruction of stubbles after the harvest. The chemical
method of control consists of application of chloropyriphos or Ekalux 5 G at
1-2 kg ai ha -1 during May and August. But control is not that effective. Pink
borer and green borer are minor pests.
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16.1.7 White Grubs (Anomala sp., Holotrichia sp., Pentodon sp., Alissonoturn sp. , and Hetronychus sp.)
These grubs are 'C' shaped and fleshy with a white or grey body. The visible symptoms of attack include dry ing of leaves, drooping of inner spindles, and finally wilting of the plant. The loss in cane yield ranges from 10-12 t ha-1 or even more if the infestation is high. T h e clump is easily pulled out since the roots are damaged. Integrated pest management is the only solution to control the pest. During the first summer showers (tropical India), the beedes emerge in large numbers to mate and these can be collected a n d killed. Collection of large number of beetles (Holotrichia serrata, Fabricus), and up to 300, 000 in one day has been achieved in the Belgaum district of Karnataka. Fluorescent light traps can be used to attract the pest. An infested field may be ploughed and the grubs, pupae, and beetles picked by hand and destroyed. Wherever feasible, puddling the soil, and paddy if grown in rotation for 2-3 seasons is a sure method of control. Varieties like Co 953 and Bo 3 are resistant to white grubs. Chemical methods of control include use of H C H dust (10%) at 10 kg ai ha - 1 or as an emulsion at 2.0 kg ai ha-1. Its efficiency can be further enhanced by the use of farmyard manure which attracts the young grubs. Quinalphos G at 2 to 2.5 kg ai ha-1 reduces the grub population, increases the millable cane population a n d yield. Successful biological control has been achieved in Hawaii and M a u r i t i u s (Blackburn, 1984). The grubs are parasitised by Campsomeris marginella modesta (Smith) and Tiphia parallela (Smith). In Mauritius, scoliid wasps introduced in t h e past for control of white grub phyllophttga Smithi are still active. But gregarines have been found to infect a high percentage of larvae (Rajabalee et al., 1995).
16.1.8 Termi tes
Large termite m o u n d s are seen in the sugarcane grown in Central and Eastern Africa. The yield loss is q u i t e variable and may extend up to 60%. Important species of termites are: Coptotermes beimi (Wasmann), Odontotermes assmuthi (Holmgr), O. obesus (Rambur ) , and O. wallonensis (Wasmann). Termites feed on soft tissue and attack setts, stalks, and stubbles. The tunnel excavated by termites is filled with soil with t h e r ind intact. There is severe germination loss and the affected cane dies. The a t t ack of termites is more severe under drought conditions and in light textured soils (sandy to sandy loam). Termite attack can be controlled
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by soil application of HCS 5% dust at 1 kg ai ha-1 or Gamma H C H (EC) at 1.0 kg ai ha -1. As a post planting operation, either aldrin (EC) or gamma H C H (EC) drenching at 1.0 kg ai ha - 1 is advocated. Equally effective is chlorpyriphos at 1.0 kg ai ha -1. Digging out termite mounds to remove the queen and spreading Vetox 85 would kill and destroy the pests. Wada (1997) informs that stem borers, soil insects, and termites can be controlled by the following measures:
(a) Planting sugarcane as far away as possible from maize, millet, and sorghum, and eliminating elephant grass from the vicinity of the cane farm.
(b) Planting healthy and clean setts which are free from borer infestation (no bored holes).
(c) Handpicking and killing larvae and adults, and burning the infested parts of the plant.
(d) Practising 2 -3 year rotation with leguminous crops.
16.1.9 Scale insect: Melanapsis glomerata (Green)
The white scale insect is a sucking pest. There are 35 species of scale attacking
sugarcane but Melanapsis glomerata is of economic importance. It is prevalent on
a wide scale in Andhra Pradesh, Uttar Pradesh, Bihar, Karnataka, Maharashtra,
Gujarat, Haryana, and Punjab. With the formation of the internodes, scales ap
pear on the cane. Heavy infestation of the scale insect starts from June and contin
ues up to December. Scales are underneath the sheath, and are hence difficult to
control. When the infestation is heavy, the entire stem is covered by scale insects
and its encrustation gives a grayish black appearance. Canes are stunted and even
tually die. The tips of the leaves show the signs of drying, and the leaves turn
yellow. The infested cane becomes shrivelled with stunted growth and has a re
duced internodal length, resulting in lowered yield and quality. Highly infested
canes pose problems in milling. The problem of scale insect is more serious in
lighter soils than in heavy soils. Ratoons are more prone to scale insect attack than
plant crop. High temperature, humidity, and drought conditions favour the scale
insect attack. It spreads through setts, ratoon stubbles, and trash. Field sanitation
is of utmost importance. Ratooning of the infested fields should be avoided. In
sect attacked seed material should never be used. Under severe infestation, trash
should be burnt. The setts can be immersed in the insecticidal solution of malathion
(0.1%) or Dimethoate (0.08 to 0.15%), or phosphomidon (0.05 to 0.08%). When
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the crop is 5-6 month old and scale insect infestation is high, monocrotophos at 1.5 kg ai ha -1 can be sprayed after detrashing. Soil application of carbofuran 2 kg ai ha -1 or Dimethoate 3 kg ai ha-1 or Aldicarb at 2 - 3 kg ai ha - 1 or monocrotophos at 3.0 kg ai ha-1 is advocated. If the attack is severe, soil application can be done at 15-30 day intervals.
16.1.10 Pyrilla [Pyrilla purpusilla, Walker)
Pyrilla is a very destructive sucking pest. The adults and nymphs suck the sap
from the undersurface of the lower leaves causing yellowish white spots to appear.
High levels of manuring, irrigation, waterlogged conditions, and lodging enhance
pyrilla build up. The hoppers exude a sweet fluid (honey dew) on which fungus
grows (Capnodium sp.). As a result, the leaves are completely covered by a sooty
mould. Due to sucking by a large number of sugarcane leaf hoppers, photosyn
thesis is affected and the top leaves dry up and the lateral buds germinate. The loss
in yield due to pyrilla epidemics is approximately 28% and the loss in sugar is
about 1.6 units. Heavy rainfall, high humidity (70-80%), and high temperature
((26-30 °C) favour pyrilla build up. Under heavy infestation, the trash which
harbours the hopper is burnt. Detrashing reduces the pyrilla population. During
the pre-monsoon period dusting with HCH (5-10%) at 20-30 kg ha - 1 , or me
thyl parathion (2%) at 12.5 kg ha-1 is recommended. Other chemicals used as
foliar sprays are chloropyriphos. (0.3 kg ai ha-1) and malathion (12.5 ai ha - 1) .
During pyrilla epidemics, aerial sprayings of insecticide has been employed
safely. Insecticides like methyl demeton (1125 ml ha -1), dimethoate (875 ml ha - 1),
fenthion (560 ml ha - 1) , malathion (500 ml h a - 1 ) , p h o s p h o m i d o n
(250-300 ml ha-1), monocrotophos (1250 ml ha - 1 ) , and endosulphan
(750 ml ha -1) gave effective control when applied aerially.
The pest has been successfully managed in recent years by releasing the lepi-
dopterous ectoparasite, Epiricania pyrillae North India.
16.1.11 White flies
There are three species of white flies, namely, Aleurolobus barodensis Mask,
Neomaskellia bergii Sign, and TV. andropogonis Corbett. Out of these, Aleurolobus
barodensis is of economic importance and severely infects cane in Bihar, Gujarat,
Haryana, Punjab, Tamil Nadu, and Andhra Pradesh.
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The nymphs of white flies suck the sap from the undersurface of the leaves which turn yellow, and pinkish in severe cases, and gradually dry up. The infested leaves are covered by sooty moulds caused by fungus Capnodium sp. which adversely affect photosynthesis. The white fly infestation retards cane growth and reduces the sugar content. Drought, N deficiency, and waterlogged conditions favour the build up of white flies. Varieties with broad and long leaves like Co C 671 and Co 775 are more susceptible to this pest.
To contain the spread of this pest, ratooning is discouraged, adequate phosphorus and potassium should be used, adequate drainage should be provide d and the affected leaves should be clipped. In Thailand, Encarria ocliai (Viggiam) and Azotus bimaculatus (Khan and Shafee) are important larval-pupal parasites of the white fly (H. Barodensis Maskell). Chemical control consists of a spray of monocrotophos (40 EC) or endosulphan (35 EC) at 0.2% after stripping the leaves bearing puparia.
Other insect pests of less economic consequence are the mealy bugs. These are ubiquitous, and 35 species of mealy bugs have been recorded on sugarcane. But the pink mealy bug (Saccharicoccus sacchari Cockrell) is possibly responsible for yield decline of commercial varieties. Mites (Acarina, Archinidd) are of minor importance and about a dozen species infest sugarcane.
16.1.12 Non-insect pests
Among vertebrate pests, rats and jackals frequently visit sugarcane fields, causing
considerable damage and yield loss. Wang (1995) has shown that wild rodents
constituted more than 50% of the rat population. The domestic species Rattus
rattus was of little consequence. Among the wild rats, Musformosanus was most
predominant. The results indicated that spring and autumn planted canes were
more favourable for wild rodents to multiply. Baiting with zinc phosphide in food
grains or dry fish at a ratio of 1 : 19 controls these pests.
Blackburn (1984) prophesied that the sugar industry would be plagued by
Eldana borer in Africa, Chilo sp. in the Old World, and Diatrae in the New World
unless integrated pest control measures were adopted.
A schedule of management practices for sugarcane grown in tropical and sub
tropical India is presented by David (1995) (Table 16.1).
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16.2
BIOLOGICAL CONTROL OF SUGARCANE PESTS
In the recent past great strides have been made in the biological control of pests. This is environmentally safe and offers better option for control of pests. Eswara Moorthy (1995) has given an elegant treatise on the biological control of pests in sugarcane.
The term biological control is used to signify the use of entomophages and entomopathogens, whether introduced or manipulated to control insect pests. In classical biological control, parasites, predators, or pathogenic microorganisms are transferred from one area to another, and their population is established to effectively parasitise the pests. This method is useful, used alone against the top borer and internode borer in tropical India, and the pyrilla, both in the tropics and the subtropics. But in several other cases, it can be integrated with varietal, cultural, and mechanical control methods.
16.2.1 Parasites
Trichogrammatids
Trichogramma sp. are widely used for the control of sugarcane borer in several countries. In India, seven species of Trichogramma and one species of Trichogrammatoidea are found to parasitise the lepidopteran borers infesting sugarcane. Of these, Trichogramma chilonis is widely used for the suppression of the internode borer. Chilo sacchariphagus indicus (Kapur) is recommended against the early shoot borer, (Chilo infuscatellus Snellen) and stalk borer (Chilo auricillus Dudgeon). On the other hand Trichogramma Japonicum Ashm is employed against the top borer (Scirpophaga excerptalis Walker). For the suppression of the internode borer, release of Trichogramma chilonis at 2,50,000 parasites ha - 1 in phases during different stages of crop growth, i.e. 25,000 parasites ha-1 during the 4th and 9th months and 50,000 ha-1 during the 5 th, 6th, 7th, and 8th months of the crop is recommended. Periodical release of T. Chilonis in contiguous cane areas throughout the year can effectively control the shoot borer. In North Bihar, weekly releases of 50,000 adults ha-1 are found to suppress the shoot and stalk borers. In Punjab, this parasite is useful against the Gurudaspur borer when releases are made at the rate of 1,25,000 parasites ha -1 against each brood.
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Isotima javensis Rohw has successfully controlled the top borer (Scirpophaga excerptalis Walker) in tropical India. Under natural conditions, it also parasitises, the Gurudaspur borer (Acigona steniellus sp. Hmpsn). Inundarive release of 125 mated female ha - 1 in the fields showing top borer incidence 'above 10%) may be sufficient for colonisation of the parasite. The parasites are released by holding the container open and moving in all directions in the field. Work in Thailand has shown that Trichogramma chilotraeae (Nagaraj and Nagarkatti), Telenomus rowani (Gahan) and Cotesia flavipes (Cameron) were the most important parasites for early shoot borer, top borer and internode borer (Suasa-ard and Charensom, 1995).
Colonization of Epiricania melanoleuca has resulted in the suppression of Pyrilla perpusilla in many parts of the country. High multiplication rate, short life cycle, and parasitization at all stages of nymphs and adults, and the good searching ability of the parasitic larvae are the main reasons for the success of this parasite. Generally releases of 4000 to 5000 cocoons, or 4 to 5 lakh eggs ha - 1 result in the effective suppression of the pest population. Stapling of leaves bearing 2 - 3 viable egg masses or 5—7 live cocoons at each release point in the field is more effective than simply scattering eggs and cocoons.
Under natural conditions, Sturmiopsis inferens T ns is active against shoot, stalk and Gurudaspur borers. The parasite has a good host searching ability and it distributes its offspring efficiently in borer tunnels. It has been tried against shoot borers and stalk borers. Sequential releases of 125 gravid females ha - 1 from the 30th to the 50th day of planting is advocated. The flies can be released by slowly moving in all directions in the field with the cages open.
Techniques have also been developed for the multiplication and field release of three species of egg parasites of Pyrilla, namely, Ooencyrtus papilionis Ashmead, Cheibneurus pyrillae Mani, and Tetrastichus pyrillae Crawford, and two parasites of the scale insect, namely, Adelencyrtus mayurai Subba Rao, Botryoideclava bharatiya Subba Rao (Eswara Moorthy, 1995).
The predators are Chilocorns nigritus F. and Pharoscymnus horni Weise which prey on the scale insect {Melanapsis glomerata). Both grubs and adults have very high feeding potential. Colonization of these predators is found to suppress the population of scale insects (loc. cit.). Release of at least 1500 beetles ha - 1 is recommended at the first appearance of the pest. The beetles can be released by keeping the container partially open and moving all over the field.
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Pathogens such as Granulosis virus are able to infect shoot borers and are found effective in suppressing the population of the shoot borers (Eswara Moorthy, 1995). It is infective to all larval stages. Another advantage is that the virus gets vertically transmitted to the offspring through adults. It is host specific, and is safe to parasites and predators occurring in the sugarcane ecosystem (op. cit.). Spraying of Granulosis virus at 106—107 inclusion bodies/ml along with surfactants like teepol or sandovit 0.05% at the first appearance of the pest controls the pest. If necessary, the application may be repeated at fortnightly intervals. The virus can be sprayed in the evening hours on the leaf whorls and stem, preferably using a high volume sprayer (Eswara Moorthy, 1995). The other pathogens are the entomogenous nematode like Heterorhabditis indicus which is active against white grubs.
16 .3
DISEASES
Sugarcane is ravaged by nearly 130 diseases but only 30 are of economic importance. Among them red rot, smut, and wilt are of serious concern. A conservative estimate shows that the loss in yield ranges from 10—15% in endemic condition. The red rot and wilt in severe form can cause total yield loss (Alexander, 1995). Based on the causal organisms, major diseases of sugarcane can be classified as under:
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Many of these diseases can be kept under check by proper seed selection, deep ploughing, crop rotation, thermotherapy, chemotherapy, and 3-tier seed programme and field sanitation. Field drainage should be provided and wild flooding should be avoided since red rot, wilt, pineapple diseases, etc. can cause considerable damage. Dipping setts in organic mercurial compound (Areton/Agallol) at 0.25% or Carbendazim at 0 .1% keeps fungal diseases in check. Moist hot air treatment at 54 °C for 4 hours has been practised. A combination of hot-water treatment (50 °C ± 1 for 2 hr) or aerated steam therapy (50 °C ± 1 for 1 hr) and fungicidal treatment (Bayleton 0.1%) has been found to be effective in controlling sett-borne infections of smut. Soil drenching with 0.4% bleaching powder has been found to be effective in reducing leaf scald incidence (Alexander, 1995). Benlate (0.1%) is highly effective against many pathogens of sugarcane such as red rot, smut, and wilt diseases. Dipping the sett in Carbendazim 0 .5% or Vitavax (0.1%) controls both internal and external inoculum. Hot water treatment is also effective. In this method setts are dipped in hot water which has a temperature of 50-60 °C for 10 minutes. Cultivation of resistant cultivars like Co 6869, CoLK 7807, CoLK 8001, and CoLK 8002 is equally important.
16.3.1 Red rot (Colletotrichum falcatum)
This is the most serious disease caused by fungus and is aptly called the 'cancer of sugarcane'. At an advanced stage of the disease, the entire top including the crown dies. The rind becomes dark. Reddish lesions are also noticed on the rind. Under high humid conditions, a pinkish powdery mass of spores of the pathogen is seen on the nodal region. Typical symptoms of red rot are observed in the internodes of the stalk by splitting it longitudinally. These include the reddening of internal tissue with white spots. The presence of these crosswise white patches is considered a diagnostic character of the disease. The diseased canes also emit a sour smell (Agnihotri, 1983). An integrated approach helps to contain the spread of red rot. In endemic areas, red rot susceptible varieties should not be grown. Since the primary spread of the disease is through infected setts, Sundara (1998) even suggested prevention of the indiscriminate movement of seed from one region to another, through legislation. The best way to manage the disease is to grow resistant/tolerant varieties. Varieties tolerant to red rot are: Co 8021 , Co 7704, Co 86010. The physiological resistance appears to be restricted to Saccharum
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spontaneum. Susceptible varieties are CoC 671, CoC 90063, and CoC 92061. The integrated approach to manage the red rot is to grow resistant varieties, provide adequate drainage, destruction of debris and crop residues and green manuring. Crop rotation with 2 crops of paddy seems to contain the spread of red rot. Ouvanich et al. (1995) reported that nine fungicides inhibited the growth of Colletotrichum falcatum and Fusarium moniliforme (wilt). The infected setts soaked in four of these fungicides had increased germination, but the pathogen was not complete ly e l i m i n a t e d . These fungicides are: Benomyl, thiabendazole, propiconazoltubuconazol, and thiophanate methyl at 500 ppm (op. cit.). Use of any of these fungicides, use of disease-free setts, crop rotation, stem borer control and other cultural practices help control red rot.
16.3.2 Smut (Ustilago scitaminea Sydow)
In India, smut is prevalent in all states but it is more so in the tropical states of
Andhra Pradesh, Maharashtra, Karnataka, and Tamil Nadu. Smutted plants are
stunted, and form excessive tillers with thin and narrow leaves. The patent symp
tom of the disease is the production of a black whip like structure from the central
core of the meristematic tissue. This flagelliform appendage commonly called
'whip' is usually straight when short and irregularly curved when 1 m long. The
disease is more prevalent in ratoons and is more pronounced in dry weather. The
loss in cane yield in plant crop is approximately 30-40% and 70% in ratoons.
The sucrose content of infected cane is reduced to 3-7%. The primary spread of
smut is through infected setts and the secondary spread occurs through windborne
black spores (teliospores). Strict roguing of diseased clumps should be done. Be
fore the silvery membrane of the whip breaks, the infected cane is put in a polythene
bag, covered and destroyed outside the field. The resistant cultivars are Co 6806,
Co 449, Co 527, etc. Hot-water treatment at 50 °C ± 1 for 2 hours in combina
tion with fungicide treatment, Bayleton 0 .1% concentration, will eliminate the
sett-borne infection.
16.3.3 Wilt (Cephalosporium sacchari Buller or Fusarium moniliformae Sheldon)
This fungal disease is widespread but is of more serious concern in Bihar, Uttar
Pradesh, Punjab, Tamil N a d u , and Gujarat. The loss in yield due to wilt is 15—
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20% with a considerable drop in sugar recovery. Patil and his associates (1995) have observed that ruling varieties like Co 419, Co 775, Co 975, Co 997, CoC 671, Co 7219, Co 1148, CoS 8407, and CoS 8315 were affected by wilt. Biotic stresses like nematodes, root borers, termites, scales, mealy bugs, etc. and abiotic stresses like drought, waterlogging, etc. predispose the plants to wilt infection. The fungi gain entry through injury. Patil et al. (1995) have confirmed that injury to roots and stalks served as an entry to the wilt pathogen. According to them the losses in cane yield due to the association of wilt and root borer were about 47%. The reduction in CCS is to the tune of 32% and sugar recovery decreased by 3.3 units (op. cit.). Wilt affected plants are stunted. This is followed by yellowing and/or withering of crown leaves. The mid-ribs of all leaves in a crown generally turn yellow, while the leaf laminas may remain green. Sometimes cavities also develop in the nodal tissues and this makes the cane shrink and become tubular, light, and hollow. On splitting open the canes at the early stages of infection, diffused reddish-brown patches are seen. Once the plants are wilted, no control measures are available. The integrated method of control comprises use of wilt-free seed material, crop rotation with paddy, and burning of trash and crop residues. Ratoons should be avoided in severely wilted fields. The variety resistant to wilt in Gujarat is a short duration cultivar Co 8338. Patil and coworkers (1995) assert that this disease can be checked to a great extent by controlling the root borer (Emmalocera depressella Swinhoe) by soil application of Quinalphos 5.0 G at 1.5 kg ai ha-1
(30 kg ha-1). Sett treatment with 0.1% Carbendazim has been recommended to avoid further spread of the disease. It is also necessary to carefully remove and destroy the wilt-affected plants. Agnihotri (1983) claims to have managed the disease by water treatment accompanied by the use of fungicides (0.1%), like benomyl, bavistin, thiram, and aretan. This author has observed that application of Mn/B to the soil (2-5 kg ha-1) or soaking of healthy setts in 40 ppm of these nutrients in solution offers a fair degree of control of wilt.
16.3.4 Pineappie disease (Ceratocystis paradoxa de Seyner)
This is an ascomycetous fungus and is widespread in Punjab, Maharashtra, Karnataka, Tamil Nadu, Kerala, etc. The padiogen enters mainly through cut ends and proliferates in the parenchymatous tissues of the internode. The pathogen also makes an entry when the stalk is damaged by borers, or when the roots are
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damaged. Drought accelerates the damage. In the initial stages, the affected sett
smells like a mature pineapple. The affected tissues first develop a reddish colour
which turns to brownish-black in later stages. In most cases setts decay and cause
severe loss in germination. Even if the setts germinate, they fail to strike roots due
to the production of ethylene by the fungus (Agnihotri, 1983). This disease is
controlled by dipping setts, sickles, and sett cutting machines in organomercurial
compounds, such as agallol, areton, or emison. Presently, setts are dipped for 5-
10 min in fungicides like Phenyl Mercuric Acetate (PMA), or benomyl, or Bavistin
at 0 .1% concentration. Sett treatment has improved germination due to hor
monal or synergistic effect.
16.3.5 Leaf spots
Among the leaf spots caused by fungi, eye spot (Helminthosporium sacchari) is most serious. Under severe conditions, a drastic reduction in the yield and quality of cane has been observed. The disease is also called Helminthosporiose. The typical symptoms are round, or oval, elongated spots on the leaves; these spots have a reddish centre and a brown border. After about a week, reddish brown streaks or 'runners' develop toward the leaf tips along the veins. The badly affected foliage looks reddish-brown (firing) when viewed from a distance. The severity of the attack is due to the toxin Helminthosporioside, which reduces the Fe content of the leaf and impairs chlorophyll synthesis. Cooler nights, high humidity as in a rice ecosystem, low soil pH, low soil potash content, and high N levels favour incidence of the disease . Cloudy weather accentuates the disease. However, with rhe rise in temperature, its incidence is reduced.
This disease can be controlled by 2 or 3 sprays of 0.2% copper oxychloride at 15-20 days interval just before the winter season. Development of a resistant variety is the final answer. Among the commercial varieties Co 62175 is more tolerant to Helminthosporium disease than Co 419.
Other leaf spots caused by Cercospora koepkei (yellow spot) are not as serious and can easily be controlled by a spray of 0.2% copper oxychloride. This author has seen severe infestation of Cercospora at a late stage in the Belgaum district of North Karnataka with no adverse effect on the yield and quality of cane.
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16.3.6 Ratoon Stunt ing Disease (RSD) (Clavibacter Xyli)
This coryneform bacterial disease is possibly responsible for varietal decline or degeneration. Diseased stools are stunted, and thin with shorter internodes. The stalks taper rapidly. The typical symptoms of RSD can be observed by longitudinally splitting mature cane, where upon orange-red or yellow-orange, usually pink-red and reddish-brown discolouration can be seen at the nodal region. It is transmitted through setts taken from diseased plants or by infected cane knives and cutting blades. The cane cutting knives should be disinfected with 1% Lysol. The insect vector for RSD has not yet been identified (Agnihotri, 1983). The development of tolerant varieties like H60-6909 and B4 1242 would give a lasting solution. Hot water or aerated steam therapy controls RSD.
16.3.7 Grassy Shoot Disease (GSD)
It is a mycoplasmal disease and is spread over the cane growing areas of the country. It is particularly severe in Karnataka and Maharashtra. The external symptoms are profuse tillering with narrow leaves and varying degrees of chlorophyll loss. The clump appears like a grass, hence the name grassy shoot. One or two millable canes from the affected clump appear 'apparently healthy' but when planted show distinct symptoms of GSD. The disease is caused by Mycoplasmal Like Organisms (MLO). This is transmitted by insect vectors like Melanaphis sacchari, M, indosacchari, and Aphis maidis. Ratoons manifest the disease more than the plant crop. The albinoid leaves contain less Mn. The general GSD affected plants contain higher amounts of amino acids, amides, and other organic acids. GSD can be controlled by thermotherapy and strict roguing. The three-tier seed programme described in Chapter 14 will completely eliminate the disease.
16.3.8 Mosaic
This viral disease is widely distributed in sugarcane throughout the world. It is transmitted by setts and aphid vectors. The chlorotic yellowish stripes alternate with normal green areas on leaves, thus giving a mosaic appearance. Mild strains of mosaic do not cause yield loss but severe strains of mosaic result in considerable yield loss. Chemotherapy or thermotherapy are of little success in the control of mosaic virus. Growing of resistant varieties (cv. CP 44101) is the solution for this
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malady. S. officinarum is highly susceptible to mosaic, whilst S. spontaneum and S.
sinense are highly resistant (Blackburn, 1984) and their inclusion in the breeding
programme will control the disease. Graminaceous species such as Echinochloa
crusgalli, Phalaris brachystachis, Lolium multiflorum, Zea mays, and Sorghum sp
are likely to act as virus reservoirs. Clean cultivation and resistant varieties will
keep the mosaic at bay.
1 6 . 4
NEMATODES
Nematodes (eelworms) are thread-like animals invisible to the naked eye. They are known to be parasitic, and about 50 nematodes species are associated with sugarcane. There are ecto- and endoparasitic nematodes. The lesion nematodes, Pratylenchus sp. are most widespread causing serious loss in yield and. quality of cane. The most important species is P. Zea. Infestation seems to be more serious in lighter soils. General chlorosis, stunting, and wilting are the above-ground symptoms while root galls, root lesions, stubby roots, and necrotic root surface are the below-ground symptoms. The loss in yield and quality due to nematode infection depends upon the population and variety. An average loss in cane yield is guesstimated at 16.5%.
The economic threshold level of P. zea for sugarcane has been estimated at one nematode cc_1 of soil or two nematodes g -1 of root. Among the nematocides Vapam is more effective than Nemagon as the former can be easily drenched. Proper crop rotations are effective against nematodes.
Sundararaj and Usha Mehta (1999) have shown that cured Press Mud (PM), if kept to decompose for a few months, is ecofriendly and has nematicidal value. Phenols, polyphenols, and several aldehydes produced by PM control the lesion nematodes. Moreover, PM is rich in carbon content and nematophagous microorganisms feed, multiply and build up their population and control nematode production.
In Australia, it was seen that legume/pasture alternate crops and fumigation with methyl bromide (MB) reduced the population of lesion nematodes. Due to pasture rotation, gram negative bacteria Pseudomonas sp., and fungi, VAM fungi were in large quantities. Rotation also arrested the yield decline possibly due to
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higher content of labile carbon (particulate matter) with increased CEC, aggregate stability, and microbial biomass.
Chemical methods of nematode control in sugarcane is given by Wada (1997) (Table 16.2).
Overall, a combination of green manuring with sunn hemp, legume break crop, heavy application of press mud (40 t ha -1) and carbofuran application at 3.0 kg ai ha -1 is a good method of nematode management.
T a b l e 1 6 . 2 Nematode control by chemical methods
Source: Wada, 1997.
287
Transgenic sugarcane: some applications of biotechnology
Biotechnology is defined as "any technique that uses living organisms or parts of organisms to make or modify products to improve plants or animals or to develop microorganisms for specific uses". One branch of biotechnology raises social and ethical issues—genetic manipulation in agriculture and food production. This branch also includes development and deployment of crops which have resistance to pests, diseases, herbicide, frost, etc., and improve N2 fixation. A fear looms that the engineered plants/organisms on commercial exploitation may lead to unpredictable and, possibly, catastrophic consequences. The genetically engineered plants may develop 'invasiveness' and become weeds with developed resistance to major herbicides. Invasiveness or weediness is precisely defined as the rate of population increase from one generation to other. But what traits enhance invasiveness is not clear.
According to Moore and Fitch (1990) it is desirable to have haploids in sugarcane breeding. The sugarcane haploids (2n = 40) were first reported in 1966 from wide crosses between S. officinarum (2n = 80) and S. spontaneum (2n = 64, 80 & 96). Each haploid was less vigorous, shorter, thinner stalked, more fibrous, and lower in sucrose than the maternal officinarum (ibid.). The complexity of chromosome behaviour has added one more dimension to the utilization of haploids in crop improvement.
Although 2n + n inheritance is common in S. officinarum and S. spontaneum crosses, n + n hybrids and haploids occur at low frequency. The n haploids are hypothesised to be apomictic, i.e. having the chromosome set of the female officinarum. The authors however reiterate that the value of haploids in rapid sugarcane improvement is unknown. Hence genetic transformation seems to favour rapid crop improvement.
Genetic transformation is the creation of a new genetically improved individual without the benefit of sexual reproduction (Irvine, 1995). The engineered plants can possess agronomically important and novel traits such as ratooning ability, insect-disease resistance, or genes for value added products (Birch, 1996). Some applications of sugarcane transformation are depicted in Fig. 17.1.
Yield (Y) is a function of genetic contribution (G), environmental contribution (E), and genetic x environmental interaction (GE)
Y = G + E + GE
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17 Transgenic sugarcane: some applications of biotechnology
High/early CCS Waxes, bioplastics, novel sugars, improved maturation digestible fibre, higher protein. Reduced metabolic waste fermentable carbohydrate
Fig. 17.1 Engineering sugarcane to produce useful products in addition to sucrose (Birch, 1996)
Genetic factors limiting yield, for instance, photosynthesis, sugar transport, storage capacity, remobilization, etc. could be addressed through engineering of plants. One distinct advantage is the reduced time scale for transgenic product development (Dunwell, 1996) as shown in Fig. 17.2.
The first deliberate transformation was achieved more than 50 years ago by Avery et al. (1944) who showed pneumonococcal bacteria could transfer genetic traits from one to another. This lead to the conclusion that the DNA is the source of genetic information, heralding the genetic revolution.
Monocots are not easily infected by agrobacterium but maize was transformed with a special technique. The most common technique is microprojectile bombardment, i.e. the forcible injection of high density microparticles coated with plasmid DNA into the target cell. In 1987, sugarcane was genetically transformed by Chen and his colleagues (quoted by Irvine, 1995) when they introduced CAT (Chloram-Phenicol Acetyl Transferase) genes into protoplasts by electroporation.
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However, they failed to regenerate plants from transformed protoplasts. Birch
and Maretzki (1993) seem to have achieved transformed sugarcane.
Fig. 1 7 . 2 Transgenic product development
Genetic transformation of sugarcane has 2 goals (Irvine, 1995). (a) The introduction of desirable traits into the existing variety with minimum
collateral change.
(b) Introduction of genes, foreign/native into parental varieties for use in conventional breeding.
In general, three types of transformations are recognized (loc. cit.) (a) Transformation may be transient, e.g. foreign gene is expressed in a cell
without being incorporated and eventually degraded.
(b) Transformation may be chimeric and in that only transformed cells divide but the tissue formed is only a part of the entire organism. However, chimeral transformation can be rescued and stabilized through vegetative propagation.
(c) Stable transformation occurs when the genetic change is formed in the entire organism and the new trait is passed on to the progeny.
There are three methods to deliver DNA systems. (a) Foreign D N A can be delivered to the target cells by electroporation
(b) Polyethylene glycol (PEG) treatment and
(c) Particle bombardment In electroporation, sugarcane protoplasts are placed in an electric current which
makes the protoplast membrane porous and thus large DNA molecules are inserted. The same effect is created by the PEG method. Employing microprojectile bombardment, Irvine and his co-workers (op. cit.) have introduced gus A (B-
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17 Transgenic sugarcane: some applications of biotechnology
glucuronidase) gene into sugarcane callus tissue and demonstrated the transient and chimeral transformation. Australian workers seem to have achieved the genetic transformation of sugarcane. Bower and Birch (1992) of CSIRO, Australia, used microprojectiles to insert NPT II (Neomycin Phospho-transferase) and gus A genes (B-glucuronidase) into sugarcane callus. The N P T II gene confers resistance to some antibiotics and geneticin is used to kill non-transformed cells. It is reasonable to propose that particle bombardment to introduce foreign D N A is the best method which includes antibiotic genes to kill non-transformed cells. Reporter genes are included to provide additional evidence that the transformation has occurred. The CAT (Chloramphenicol Acetyl Transferase), gus A (B-glucuronidase), and luc (luciferase) genes are common reporter genes used in plant transformation. The gus A gene is the most popular reporter gene to signal transformation and its assay is simple.
In transformation, the choice of plasmids for DNA transfer is important, particularly the size. Plasmids are circular D N A sequences (1—400 kb). The plasmids must be large enough to carry genetic substances but not so large as to be unstable. The plasmid P Emu promises to be a powerful tool in sugarcane transformation. This plasmid Phosphorus Emu (65 Kb) contains enhancer sequences from agrobacterium and promoter sequences from maize which make transformation easy in monocots. Choosing a promoter is critical in sugarcane transformation.
The first report of herbicide resistant transgenic sugarcane comes from Gallo-Meagher and Irvine (1996). They obtained herbicide resistant transgenic sugarcane in the commercial cultivar N C O : 310 by introducing the bar gene. Most of the transgenics displayed resistance to the commercial herbicide ignite (glufosinate ammonium). Non-transformed plants showed a high degree of necrosis even at 0.2% ignite. On the other hand, transformed plants showed minimal levels of necrosis even at 2% ignite. Indications are that the bar gene can be stably incorporated into the sugarcane genome. Further, its phenotypic expression can remain unchanged following commercial propagation practices. Further more, transformed plants will also have an integrated desired agronomic gene, a phenomenon known as co-transportation. They can also be tested for the expression of the desired agronomic gene or co-expression. For practical purposes, it is desirable to have a high frequency of co-transportation and co-expression. Sometimes the expression of introduced genes is turned off—a process known as transgene silencing.
The clarion call is that transgenic commercial crops like sugarcane, sugar beet, and tobacco produce drugs. No pharmaceutical has the market demand of 100 million
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tons a year that sugar enjoys (Irvine, 1995). This is in essence, molecular farming (Hunsigi, 1998). But sugar and alcohol will remain the main products of sugarcane.
The commercial exploitation of transgenic crops requires caution. It must be convincing to organic farmers and environmentalist groups. The industry must demonstrate that Genetically Modified (GM crops) have no adverse ecological impact (Masood, 1998). In other words, genetically modified plants will need thorough field testing before commercial cultivation to convince agronomists, environmentalists, and the end-user, i.e. farmer.
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Box I
Terminator seed technology
The process involves expression of two gene systems where one is responsible for phenotypic alteration of the embryo and the other controls the embryo.
Thus the Gene-I blocks the germination if expressed at the time of germination. Gene II encodes for recombinase which is important for the expression of the gene-I system. These genes are supposed to be transpos-able elements of bacterial origin.
An important point is the expression of the gene-II system by tetracycline. Therefore, application of tetracycline before marketing is an indispensable step of this seed technology.
M. S. Swaminathan, leading Agricultural Scientist claims that at present, we do not have any mechanism to stop such technologies from seeping in. A challenge is to develop highly sophisticated molecular probes to check the dreaded seed in the import shipment itself.
According to terminator seed technology, a variety with a terminator gene will bear normal seeds but seeds fail to germinate in the next generation. They can encourage as many selfings as they wish and also terminate viability of seed at any time by tetracycline treatment. But this lethal technology will not find field in the vegetatively propagated crops like sugarcane, potato, etc.
Source: Rani Gupta, 1998, Sujay Rakshit, 1998.
Sugarcane simulation models
GENERA LI A
In the early 1970s, De Witt termed model as a cumbersome method of curve fitting. A model may be defined as a summary of a coherent body of experimental data in a logical structure, and can be a mere hypothesis or concept. Models are important research tools but cannot replace observation, experimentation, and experience. According to Montieth (1996), a crop model can be defined as a quantitative scheme for predicting growth, development, and yield in a given set of genetic coefficients, and relevant environmental variables.
There are three types of models: empirical, mechanistic, and comprehensive. There are teleonomic models which have set goals, sometimes called teleological, and are goal setting and attempt to answer 'whys' and 'hows'. An empirical model is mathematically descriptive or is curve fitting of observation data which does not permit extrapolation. A mechanistic model is more comprehensive and takes into account all the processes and sub-processes. Extrapolation is possible in mechanistic modelling. De Witt (1970) gives an early account of concepts in modelling and a detailed treatment is furnished by Thornley and Johnson (1990). Both complex and simple models are needed. In reality most crop models are a mixture of empiricism and mechanism.
Baker (1996) concluded that crop modelling is primarily heuristic (guiding in discovery or to find out), and models cannot do all that are being promised. Nevertheless, crop modelling is playing a valuable role and this is destined to increase. Scientific models are mechanistic while the best engineering models are based on robust empirical relationships between plant behavior and major environmental variables.
Fundamentally, models simulate the growth of crops based on the response of ecophysiological processes to the environment. De Witt and Penning devaries (1982) distinguished 4 production situations.
I. Production situation-1. Here in this situation water and nutrients are available to crops in ample supply. Crop growth and production are determined by radiation, temperature, and species characteristics, or say cultivars.
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18.1
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II. Production situation-2. For at least a certain period, crop growth is limited by water supply in a growing season. A water balance of the soil has to be included in the model.
III. Production situation-3. In this system, water and nitrogen limit crop growth for at least a certain period of the growing season. This is the situation in many rainfed agro-ecosystems.
IV. Production situation-4. In this situation, phosphorus and other nutrients limit crop production. This is a complex situation where no fertilizers are added.
In all the above production situations the effect of growth reducing factors— pests, diseases, and weeds can be included. Simulation models are being used to
(a) predict adaptation to specific environmental conditions. (b) predict response to alternative management practices.
(c) predict the behaviour of complex cropping systems under different agro-ecological situations.
(d) predict short-and long-term changes in soil fertility and productivity due to management.
(e) quantify yield gaps related to weather, genetic, and management protocol. (f) improve management or minimise risks.
(g) take policy decisions on a scientific footing.
(h) assist in management decisions, cultural practices, fertilization, irrigation,
pesticide application, etc. (i) predict soil erosion, leaching of agrochemicals and to understand the effects
of climatic changes in 'large area yield' forecasting, (j) use historical weather data to optimise planting date, plant density, row
spacing, choice of a cultivar, fertilizer application to different soil types, (k) predict photosynthesis respiration and tissue synthesis to integrate and to
describe Radiation Use Efficiency (RUE). A model in a sense is synonymous to theory, hence it needs validation or veri
fication. Validation is equivalent to testing null hypothesis. Further, models need to be tested on diverse environs. Also it is not necessary that models test only final yield; intermediate processes like canopy photosynthesis, respiration, transpiration, N2 fixation, and assimilate allocation, etc. are also tested.
Two tilings stand out in the modelling approach. Firstly, when the climatic data is fitted into the crop models, a large gap is seen between the actual and the
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simulated model. This means there is a potential to harness the additional yield.
The yield gap is to the tune of 30% in most of the crops. Secondly, empirical
models have shown that N concentration in leaves of most crops (petioles in
dicots) must be kept above 2.5% at grand growth phase to harvest a rich crop.
18 .2
EMPIRICAL MODELS
Many empirical models are regression equations and consist of functions that are
chosen arbitrarily. They do not permit extrapolation. The most widely used ap
proach is the rectangular hyperbola to describe the density response (Kropff and
Lotz, 1993).
where Y. = Crop yield in monoculture g m-1; Nc = Plant density in numbers
m - 2 ; bo = Y—intercept; bc = the slope of the curve.
Many empirical models have been developed to describe the effect of weeds on
crop yield loss (Kropff and Lotz, 1993).
where YL - Relative yield loss; a = bcw/ao describes the yield loss caused by adding
the first weed; bcw = measures intraspecific competition between crop and weed;
ao is equal to 1 /wcc, the reciprocal of the average weight per plant in a weed free
crop; Nw is the weed density.
Of the weather parameters, temperature is fundamental to plant growth and development, and has been extensively used in simulation models to predict yield as influenced by the temperature regime. Vincent (1989) has employed thermal time to study the response of crop plants to temperature in the modelling approach. Thermal time (0) is defined as
where T—daily mean temperature; Tb—base temperature, 10 °C.
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According to Vincent (op. cit.) thermal time to establish canopy in most crops
varied from 381 to 510 degree days.
Nutrient modelling in sugarcane has been attempted by Hunsigi (1993a). The
response of sugarcane to applied nutrients is well predicted by quadratic, square
root, and exponential functions. Or a more direct approach to establishing the
needs of the crop is given as:
where Nc = uptake of N for maximum yield; Nf= fertilizer need, Cf = fertiliser use efficiency, Ni = initial quantity of mineral N; Nm = estimated mineralized N for the crop season.
An estimate was made for sugarcane (Cv. Co 62175) grown an alfisols of Mandya, where N uptake Nc = 204.94 kg ha - 1 , initial mineralized N, Ni = 62 kg ha - 1 . The mineralized N for the crop period Nm = 84.8 kg ha -1 . The fertilizer use efficiency, Cf was assumed at 0.5
Another empirical model which has been successfully used to predict N response to sugarcane is
where Ymax —maximum cane yield at high N value; Ns —effective residual soil N;
N—applied N; K—parameter determining the initial slope. This has been employed with a significant coefficient of determination (R2).
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18.3
MECHANISTIC MODELS
In all this, quantified processes have a sound physical and physiological basis, and permit extrapolation.
Jones ec al. (1989) have developed a simulation model for sugarcane grown in Australia. This model is known as the AUSCANE model. This is a modified version of the EPIC crop simulation model for sugarcane. A wide gap between the theoretical and actual yield has been highlighted in a recent symposium— 'Sugar beyond 2000' in Australia. This gap could be as wide as 30-40%.
Fig. 18.1 Flow chart of soil water management in cane growth model (Schematic)
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Biological limits to sugar yield and yield plateaus in cane and sugar yield are also stressed. Yield plateaus in cane and sugar yield are due to the limits of genetics, water, radiation, and N availability.
A flow chart of general soil-water management in a crop growth model is presented in Fig. 18.1 (Schematic).
From Fig. 18.1, knowing the daily water status, we can estimate the yield reduction due to stress.
A function of the type used is:
where Y = actual dry m a t t e r yield; Y = potent ia l dry mat te r yield;
T = transpiration; T = potential transpiration.
The Stress Index (SI) is also computed as:
Recognising that radiation and water availability are limiting cane and sugar
output in the tropics and subtropics, the model can be constructed as shown in
Fig. 18.2. The input data include thermal time, heat units, daily radiation, water
supply, plant density, and N supply.
M. K. Wegner (pers. commn.) has concluded that a combination of simulation modelling and economic analysis lead to risk analysis in sugarcane production. It is observed that irrigation production was risk efficient and should be selected by cane growers in preference to unirrigated production. Perumal (1995) has developed a computer aided foliar diagnostic model (ISFY). The ISFY model takes inputs such as sheath moisture, soil texture, soil chemical constituents, and P 2 0 5
content of juice. Sheath moisture depends on the variety, planting/ ratooning season, irrigation and drainage, and management practices.
The modelling of crop—weed interactions is dealt in detail by Kropff and Van Laar (1993). The model I N T E R C O M has been developed to quantify intercrop competition. The main objective of the INTERCOM model is to provide a tool to analyse complex interactions between plants that compete for sources such as light, water, and N. A special emphasis is on crop—weed interactions and also the different effects of varying weed species. The model is robust and designed to
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account for the effects of temperature, radiation, rainfall, and analyse several com
petitive situations in different agro-ecological environments.
Fig. 1 8 . 2 Flow of information in a sugarcane model
Taken overall, models are research tools which help in providing a deeper un
derstanding of plants in relation to edaphic-climatic factors and other variables.
The singular contribution was to model the impact of increased atmospheric tem
perature and CO2 concentration (Greenhouse effect) on crop growth, develop
ment, and yield. Modelling is destined to play a major role in the future produc
tivity of crops despite the fact that the conclusions will be challenged.
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Ripening, maturity and harvest
Ripening in cane can be conceived as a result of shift in photosynthate partitioning from growth to storage (Alexander, 1973). Clements (1980) has described sugarcane ripening as a physiological senescence intermediate between rapid growth phase and ultimate death of plant. In a simple way ripening is storage of excess sucrose. Physiologically, there is a decline in acid-invertase activity which motivates sucrose retention rather than utilization. The primary concern of the plant at this stage is sugar storage rather than utilization. Arguably, Alexander (1973) states that the ripening process is conveniently depicted as culmination or perfection of maturity. The bottom line is that ripening follows naturally upon depletion of soil moisture and soil N which restricts further growth without much restriction of photosynthesis. Thus ripening closely parallels the process of ageing and maturation without being synonymous (loc. cit.).
As the plant experiences maturation, the growth processes tend to slacken with a concomitant depletion of tissue moisture and tissue N. The sheath moisture index drops down by about 10% (-82% to 72%) and N index falls from about 2.0% to 1.75%. Potash index (3-6 leaf sheaths) remains steady at 2 .0 -2 .5% from 6—12 months. This element converts reducing sugars to recoverable sugars and and also increases fibre content by lowering tissue moisture (Fig. 19.1).
This also contributes to the hypothesis that sugar and fibre are not incompatible. Primary Index (PI) is also suggestive of ripening. PI is defined at total sugar level of the elongating cane sheaths (3—6 nos.) expressed as percent of dry matter. At maturity PI is 10.0%. Lower values indicated that the growth has superseded sucrose storage. As a matter of fact, PI defines energy potential of a local area and indicates the limits within which efficient production can be attained.
Lingle and Irvine (1994) reiterate that ripening is indicated by a decrease in elongation rate, increase in total sugar concentration and increase in sucrose per cent of total sugar over successive sampling dates. During the ripening phase sugar gets accumulated in cane internodes when they start elongating and continues even after elongation ceases. They concluded that the activity of Sucrose Synthase (SS) does not appear to be related to ripening. The ripening observed in the study was evident from an increase in total sugar concentration in internodes from the upper 3rd of the stalk. In other words, natural ripening was indicated by an increase in sucrose to total sugar ratio in the uppermost internodes.
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19 Ripening, maturity and harvest
Fig. 19 .1 Effect of potassium on sucrose and fibre percent cane (diagramatic)
Lingle (1997) asserts that the Enzyme Commission (EC) comprises enzymes of sucrose metabolism, namely, invertase, Sucrose Synthase (SS) and Sucrose Phosphate Synthase (SPS). The activity of SS is mooted as a measure of sink strength. Moore (1995) reported two sucrose synthase iso-enzymes, i.e. SS1 and SS2. Total sugar and sucrose concentration increase, while SS, acid, and neutral invertase activity decrease during internode maturation. It is therefore, tempting to conclude that SS, acid and neutral invertase activities suppress sugar accumulation. Indirect evidence comes from glyphosate application which inhibited growth and reduced the activity of acid invertase with a consequent increase in sucrose and total sugar concentration. Glyphosate, however, did not have any influence in SS activity. It is, therefore, suggested that it is the acid-invertase activity and not SS that promotes growth and suppresses sucrose accumulation.
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Fig. 1 9 . 2 Sugarcane ripening zones in India. Based upon Survey of India map with the permission of the Surveyor General of India.
The territorial waters of India extend into the sea to a distance of twelve nautical miles measured from the appropriate base line.
The boundary of Meghalaya shown in this map is as interpreted from the Assam Reorganization (Meghalaya). Meghalaya is an autonomous State within the State of Assam.
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19 Ripening, maturity and harvest
Lingle (1997) observed that SS activity like invertase activity was greatest in the youngest internodes and declined to a steady state by 200 °C d. But total sugar concentration continued to increase (nearly linear) up to 400-600 °C d. The author concluded that internodes that developed late, reached maturity in fewer heat units than those that developed early in the growing season. Admittedly the water content of all internodes decreased from 900 g kg -1 to 720 g kg - 1 .
Natural ripening is induced by growth restriction caused by environmental conditions associated with the harvest period like low soil N, low soil moisture, and cool ambient temperature. Reduction in growth is often correlated with a reduction in acid-invertase activity. In difficult-to-ripen areas such as the coastal regions of India, high temperature and high humidity are conducive for growth but not for sugar accumulation. There is no distinct ripening phase. In these areas sugarcane internodes have intense activity of acid invertase and are characterised by low sugar recoveries. Figure 19.2 depicts the sugarcane ripening zones of India as presented by Srivastava et al. (1988). The North and Central parts of India have good to fair natural ripening conditions. It is interesting to note that self defoliating cultivars with a minimum of 4—6 active functional leaves had shown natural ripening with acceptable levels of sugar recovery.
1 9 . 1
RIPENING METHODS
Alexander (1973) has presented the historical developments in the use of chemi
cal ripeners. Attempts were made to ripen cane by use of molasses, 2, 4-D, maleic
hydrazide, TIBA (2, 4, 5 Triodobenzoic acid), Sucro (Esso 59—4), Trysben (TBA),
boron, molybdenum, monopotassium phosphate, Cycocel, GA and sodium meta-
silicate ( N 0 2 , SiO3 9H2O). Silicon was effective in in vitro inhibition of both
catalysts—amylase and invertase. Calcium silicate improved cane quality as well
as tonnage. Manganese tended to restrict invertase and a combination of
Si (500 ppm) and Mn (100 ppm) had depressed the invertase levels with a major
increase in sucrose levels. Silicon sprays tended to lower the phosphatase and
ATPase levels. Suppression of acid phosphatase benefits sucrose synthesis. The
pyridine analog 6-azauracil suppressed invertase and was accompanied by sucrose
increase. Several methods ranging from cultural techniques, use of oils, growth
promoters or inhibitors to the use of nutrients, defoliants, desiccants and ripeners
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have been employed to ripen cane. But a more practical method is to withdraw water 4 -6 weeks prior to harvest (cut-out period) in non-monsoon climate, where rains do not interfere in the natural ripening. Different ripening methods employed to ripen cane are presented in Table 19.1.
The ripeners of economic impor tance are Polaris (4.0 kg ha"1), Ethophon (0.5 litre ha-1) and Glyphosate (0.5 litre ha-1). Fluazifop or fusilade super has been recognised as an effective ripener (sucrose loader/enhancer) in recent times. Countries like South Africa, Australia, Cuba, etc. use chemical ripeners extensively.
Ripeners help to extend the crushing season by opening early and crushing late. Irrigated sugarcane was ripened through regulating the amount of irrigation water applied close to harvesting—a process known as 'drying off. There was some evidence that 'drying off' may produce better cane quality than a well irrigated crop ripened with chemicals. It is for this reason that a short drying off is advocated when chemicals are used to ripen the crop. The chemically ripened crop has better purity, an evidence of ripening, and results in better sugar recovery.
Donaldson (1999) reported that polado or glyphosate was used extensively as a sugarcane ripener in South Africa. But it lost favour since the ripener had an adverse residual effect on the sprouts of ratoons. Later on fusilade and fusilade super (fluazifopbutyl) were tested as sugarcane ripeners. There were severe symptoms of leaf scorch and necrosis of stalk meristematic region. But this is also an indication of ripening. Varietal differences were observed with regard to response to fusilade super. According to Donaldson (op. cit.) response of N12 was better than N16 to fusilade-super. The reason was N12 tolerates stress better by leaf rolling. Incidentally N Co 376 also responded better to ripeners. It was concluded that with the onset of stress, abscisic acid levels rise, and esterase activity decreases in the plant and both may decrease the activity of fusilade-super (fluazifopbutyl). For some varieties a higher dosage of fusilade super (0.75 g ai ha-1) was tried but it resulted in a poor ratoon crop. To obtain response to a wider varietal spectrum, a combination of ripeners was used. Ethephon spray (Ethep-hon is the trade name for Ethrel) was followed by fusilade super to varieties like N 19, N C O 376 and N 25 with good success. The average gain is about 0.8 t ha -1
sucrose per year. But the gain in 3-crops was 3.2 t sucrose ha - 1 from glyphosate. The spray equipment employed were mist-blower and overhead sprinkler. In India this author has attempted knapsack spray with telescopic attachment. Ultra low volume spray application is recommended. A gap of 45—60 days should be observed between the spray and harvest.
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T a b l e 1 9 . 1 Methods used to ripen cane
Method Remarks
l. Cultural
2. Plant or animal products
3. Growth promoters
4. Growth inhibitors
or antiauxins
5. Plant nutrients
6. Defoliants or desiccants
7. Antibiotic or
antimicrobial agents
8. Chemical ripeners or
sucrose loaders
(sucrose-enhancers)
Withholding irrigation 4—6 weeks prior to harvest
(cut-out period), tying or supporting (wrapping and propping) the cane.
Molasses, petroleum products such as sucrol (Esso
59 G), FS 40 (diesel oil plus penta-chlophenol plus
2, 4-D). Self defoliating cultivars
2, 4-D, GA, 2, 3, 6-Trichlorobenzoic acid (TIBA)
Maleic hydrazide, Cycocel, abscisic acid (ABA)
Boron, monopotassium phosphate, molybdenum,
manganese, silicon, sodium metasilicate
Gramaxone, Reglone
Naramycin A, Streptomycin sulphate,
magnamycin, nystatin, novobiocin
Cycocel (CCC)
Embark (Mefluidide)
Dowpon (Delapon)
Asulox (Asulam)
Polaris
Etherel (Ethephon or Flordimex)
Glyphosate (Polado or round up or lider)
Fluazitop (fusilade) or fluazifopbutyl
ethephon + fuazitop (2 sprays each, not to mix)
ethephon + glyphosate (2 sprays each, not to mix)
gallant super (haloxyfop-R methyl ester)
Registered in S. Africa as ripener, under trial)
Source: Hunsigi, 1993a. Data modified and adapted.
Donaldson (op. cit.) concludes with optimism that chemical ripening has a distinct possibility in irrigated areas, with a long milling season and cane payment schemes that reward better quality. There is a need to unravel the process of dry matter partitioning that favours the accumulation of sucrose. Future improve-
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ments can be expected by creating chemical ripening schedules based on growing degree days. Better results are also anticipated if the chemical ripening is combined with a short period of water restriction (drying off). Recently gallant super (haloxyfop-R methyl ester) has been registered as a ripener in South Africa and its performance will be watched with interest.
Further evidence comes from Cuba where fluazifop is the most widely used chemical ripener for sugarcane (Cutino et al., 1995). Cutino and his co-workers (1995) observed that fluazifop and glyphosate were economically more favorable than ethephon and fluazifop. The authors have recommended various dosages for cane grown in Cuba (Table 19-2). Varietal differences were also marked. The gain in sugar following chemical ripening ranged from 0.5 to 2 t ha-1 when the interval between spray and harvest was 45—60 days. In Australia, an increase in CCS between 0.4 to 1.3 units was observed, when cane was treated with ethephon.
These ripeners increased pol % cane in most cultivars. Post-harvest measurements like tiller count, and population at 2-5 months (stubble crop) did not change following ripener treatment. The effect of fluazifop at 0.056 kg ai ha-1 on pol % cane (Cv. M 5514) is shown in Fig. 19.3.
In India chemical ripening in commercial plantations is practically negligible. The most probable reason is that the payment is made on tonnage basis rather than on cane quality. Moreover special equipment is needed to spray ripeners on tall and lodged cane. Hence this calls for mechanization of cane industry. Nonetheless, 'cut-out period' or 'dry off' for 4-6 weeks is mostly observed in many plantations.
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Fig. 1 9 . 3 Effect of fluazifop 0.056 kg ai h a - 1 on cultivar M 5514 (Cutino et al., 1995)
1 9 . 2
METHODS OF CANE PURCHASE
No universal method is available to purchase cane but some guidelines are followed in each country where quality of cane is taken into account. It is in Australia that cane is taken on quality basis. But at the end of the season sugar recovery becomes the basis for cane pricing. The base price is fixed at 8.5% of sugar recovery and every increase in the unit sugar bagged will get a proportionately higher cane price. Efforts are made to avoid stale cane and fresh cut canes arrive at the mill within 18-24 h. Burnt cane is usually rejected or the supply of such cane is heavily penalized.
Some important methods of evaluating cane include the following. 1. The Java Ratio (JR) is an arbitrary milling ratio. JR does not take into
account the different fibre content of different varieties (Meade and Chen, 1977).
JR = Sucrose (pol) % cane / Sucrose (pol) % first expressed juice
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2. The SJM formula proposed by Deerr postulates that for a given juice of J purity and producing sugar of S purity with molasses of M purity, the percentage of total sugar (pol) in the original material to go into sugar will be:
SJM=100 S ( J - M ) / J ( S - M )
This formula envisages that the pol in the original material separates into that which goes into sugar with the remainder going to molasses. It does not take into account other losses.
3. The pol ratio (PR) is the direct measure of cane quality expressed as Tons Cane (TC)/Tons Sugar (TS).
4. Arceneaux's universal equation is given as:
S' = Sx-By
where S' is the available sugar (%), S is the pol (sucrose) in juice, B represents the brix of primary juice and x and y are the factors connected with the fibre content of cane and the brix and pol of juice.
5. Australia was perhaps the first country to make payment for sugar rather than cane and the grower is rewarded according to the sugar content of the sugarcane. The Australian Commercial Cane Sugar (CCS) formula is given by Meade and Chen (1977) as:
CCS = 3P/2 ( 1 - [F + 5]/100) - B /2 ( l - [F + 3]/100)
where P is the pol percentage of the first expressed juice, B is the brix percentage of the first expressed juice and F is the fibre percentage in the cane.
6. The Winter and Carp formula is widely accepted throughout the sugar world but has undergone many modifications (Meade and Chen, 1977). The formula is:
x = S ( 1 . 4 - 4 0 / P )
where x is the available pol (sucrose) percentage in cane, S is the percentage pol in juice and P denotes the purity of juice.
7. The Louisiana method used by the US Department of Agriculture envisages a 'standard cane' having 12% pol with a juice purity of 75%. Thus, a premium is added or penalty deducted when the 'normal juice' (first expressed juice or laboratory mill juice) exceeds or fails to reach this quality (Blackburn, 1984).
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8. In Spain a simplified yield of commercial sugar (Y) is computed by assuming an average of 0.0779 (Barnes, 1974):
Y = 0.779 P - 3 . 0 5
where P is the pol percentage of the first expressed juice. The loss during process is assumed to be 3.05%.
9. ERS (Estimated Recoverable Sugar).
In South Africa, ERS is used to measure the cane quality;
ERS = Sucrose - 0.485 (non-sucrose %) - 0.056 (Fibre %)
This takes into account the losses in crushing and process.
10. More recently Ahmed et al. (1998) have presented improved formulae for evaluation of cane quality. The improved empirical formulae estimate fibre, sugar recovery and sugar or pol % cane.
(a) Fibre % cane (f) = [(1 - F)/(L6 )]x 100
where F is the factor for maximum juice per unit cane derived from the equation
F = E2/0.84
(b) E is the extracted juice per unit cane at bagasse with moisture of 0.51
per unit in bagasse. In case of moisture content being more than 0.51
per unit in the final bagasse.
(c) E = e + ( m - 0 . 5 1 )
where e is the extracted juice per unit cane, m is the moisture per unit
bagasse, 0.84 is the constant for maximum juice recovered at 0.1 fibre
per cent cane.
(d) Sugar recovery % cane = [S- (B - S) 0.32] F
where S, B are sucrose and brix per cent juice. 0.32 is a constant de
rived from lowest molasses purity (0.2425) and F is the factor for
maximum available juice per unit cane.
(e) Sugar or pol % cane = [1 - 1.2f] S
where ( 1 - 1 . 2 f) is the total juice per unit cane and S is the sucrose per
cent juice. The factor 1.2 represents the quality of fibre along with
mechanically nonseparable brix free water per unit of dry fibre, f is the
quantity of fibre per unit cane, estimated by the formula (a).
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11. Recoverable Cane Sugar method (RCS) RCS method combines Australian CCS and Winter-crop formulae and is
recommended by the International Commission.
RCS = 1.05 (1.4 pol % cane - 0.4 brix % cane) where Brix % cane = Brix %
juice [1 - (F + 5)/(100)]; and pol % cane = pol % juice [1 - (F + 7)/(100)]
where F = fibre %
12. Hugot formulae
% extractable sucrose = K [(pol % juice - 0.3 brix % juice) ( 1 - 1 . 4 F)]
% extractable cane sucrose = K brix % juice [(purity ~ 30)/100] ( 1 - 1 . 4 F)
where F = fibre %. The coefficient K for clean samples taken in fields is 0.85 and for untreated samples taken at factory is 0.95.
It is opined that the empirical Australian CCS formula or Winter and Carp formula gives a better estimation of cane quality and is user-friendly.
1 9 . 3
HARVEST STRATEGY
The harvesting includes cutting, cleaning, loading, and transport and constitutes nearly 30—40% of the production cost. The harvest strategy includes, inter alia,
(a) ensure adequate cane supply (b) cane quality is judged by pre-harvest maturity survey or Small Mill Test
(SMT)
(c) proper age of harvest depending on the variety (d) harvest of flowered and ratoon cane
(e) efficient cane transport
(0 acquiring labor for efficient harvesting (g) crushing of burnt or stale cane
(h) maintaining proper communication system and, finally
(i) computerization of cane harvesting programme. Supply of adequate cane to the mill is essential. A 2500 T C D plant requires
120 t cane per h and there must be at least 12—15 trucks stationed in the cane yard. First ratoon area is taken and cane supply should be from different sections/
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19 Ripening, maturity and harvest
regions. Varietal spectrum ensures longer crushing season and very good seasonal sugar recovery. To avoid diversion of cane to jaggery units, when the jaggery prices are high, cane should be drawn from the reserve area. Normally quota system is followed. If the farmer has registered 2 ha with the factory, he should supply about 200 ± 1 0 tons of cane to the mill.
Cane registration is done by the field staff and the date of planting/ ratooning is recorded. It is worthwhile if plot history, varieties grown, amount of cane supplied, etc. are recorded in a floppy.
Opt imum age of harvest should be ensured. Tendency to supply immature cane should be avoided. Varieties with differing maturity periods are planted and the supply is according to their peak sugar level. Bulk planting takes place in about 2 - 3 months time; the harvest age could be 14-16 months. This late harvest not only reduces sugar recovery but adversely affects the ratoon crop. A plant of 2500 T C D can have the following varietal spectrum.
(a) Ruling variety 50%
(b) Ratoons (1st to 3rd ratoons) 30%
(c) Early maturing 10-15%
(d) Others 5-10%
In peninsular India, the optimum crushing period is 280-300 days while in
the subtropical belt it is 180—200 days. Flowered cane tends to accumulate more
sugar as growth has practically ceased. But flowered cane has to be harvested within
2 -3 months of flowering. If delayed, there is pith formation, side shooting, and
lowered juice extraction with consequent reduced yield and sugar recovery. Non-
flowering canes like H 2 0 4 5 , B 37172, KH 3296 help to extend the crushing
period.
The ideal weather conditions for harvest are rain-less period, low to moderate
humidity (45-65%), cooler nights with warm days and bright sunshine hours.
The rains interfere not only with the harvest but also with the transport of the
cane to the mill.
A distinct 'cut-out' period of 4-6 weeks has to be observed. This is abstraction
of water/controlled irrigation to ripen cane. Ripeners are not used in India on a
commercial scale but 'dry off' or 'cut-out' period is the practical method to ripen
cane. The different ripening methods are given in Section 19.1.
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19.3.1 Pre-harvest maturity survey
This is the most essential component of a harvest strategy. A mature cane assures good tonnage and sugar recovery. Varieties differ in their maturity period. The same variety differs in maturity due to edaphic conditions like water logging, high and late N application, saline/sodic conditions, etc. Hence a pre-harvest maturity survey is done on standing cane. Hand refractometer (HF) is used and random samples are drawn at least at 4 corners of the plot. Normally cutting permits are issued if HF values range from 20-24 ° brix. In progressive sugar factories even small mill test is done, and parameters like brix, pol and purity coefficient are determined. T h e sheath moisture index of tissues (3, 4, 5, 6 top leaf sheaths) can be determined. In immature cane, sheath moisture index is high, say about 8 0 -82% while in mature cane it is 72-74% Trials have indicated that harvesting based on a pre-harvest maturity survey alone gives increased sugar of about 1.0 unit.
19.3.2 Methods of harvest
Normally manual harvesting is done and contract labour is procured from nearby-places. In irrigated areas labour shortage is acute and adequate labour arrangement has to be made. Labour costs are paid normally on tonnage basis. It is worthwhile if the factory arranges the labour for harvest and payment is made weekly in a worksheet signed by the farmer. In North India labour is relatively cheap. Labourers harvest the cane and the wages are in kind—they take the cane tops, green foliage a n d grasses. This scenario is fast changing and acute labour shortage is observed in Punjab and Haryana. Due to industrialization, migration of labour to urban areas takes place.
Appropriate tools are also necessary for efficient harvesting. Curve sickle is an effective implement to harvest cane and it can clean the cane by removing trash, adhering roots, etc. A hand axe shaped like 'Parasuram axe' is equally effective. The Indian Institute of Sugarcane Research (IISR), has developed a hand stripper, but it is not commonly used. But the stripper is very useful when certain cane varieties have spines. For better yield of cane and sugar, it is essential to harvest the cane at ground level. Sundara (1998) has estimated that 5 to 10 tons cane or 0.5 to 1.0 ton sugar per ha is lost due to improper harvesting. Moreover, if the cane is not harvested at the ground level, the ratoons may be adversely affected due to lack or anchorage and support.
Sugarcane in agriculture and industry
312
19 Ripening, maturity and harvest
Some varieties like Co 62175 have 5-6 immature top internodes, which contain more moisture and less of recoverable sugar. The tops should be removed and cleared from trash and other extraneous matter. The binding material and trash can reduce juice extraction with a drop in sugar by 0.3 to 0.5 units. However, the permissible trash and other extraneous matter under mechanised harvesting is 7% and manual harvesting is 2 to 3 % .
An efficient transport system is essential and trucks are normally hired by the factories. Large trucks can carry 10—14 tons of cane. But it is worthwhile to transport cane by tractor trailers. In North Karnataka usually 2 trailers are hitched to a 35 HP tractor and 12-14 tons cane can be transported to the mill. The network of village roads should be properly maintained for efficient cane haulage. In black soil regions roads get sticky with a slight rainfall and this impairs cane haulage. The transport distance should be within a radius of 30 km. For a shorter distance of 10 km or less, sugarcane can be transported by bullock carts. It has been observed that cane transported by bullock carts comes to the yard in a fresh condition. However at the cane yard, water facilities, fodder feeding trough (manger), etc. should be provided. At the yard, cane has a standing period of 2 -3 hr but the harvested cane should be crushed within 8—10 hours.
Post-harvest deterioration can cause serious losses due to delayed crushing. Break downs in the factory or transport problems may cause the cut cane to be kept in the field/cane yard for over 48 hours. This leads to fast deterioration. In tropical regions the loss in yield is in the range of 1.5 to 2 .5% for every 24 hours of storage after the cane harvest. Higher losses up to 2 5 % have been reported due to delay by a week in crushing the harvested cane. For the first 48 hours the loss in sucrose of harvested cane is negligible but further delay would lead to a drop of 0.1 to 0.12 units for every 24 hours delay. But from 72 hr onwards, rapid deterioration and fall in quality was observed. Post harvest deterioration is due to infection by Leuconostoc. If the surface area of cut ends is more, the infection of Leu-conostoc is more serious and souring of the cane juice occurs, with high amounts of sugar entering the molasses.
Attempts have been made by the author to control post harvest deterioration by covering the cane by trash/straw, spraying water or even spraying 1% urea solution. The integrated method to control post-harvest deterioration includes: keeping harvested cane in shade, covering with trash and sprinkling water. Leuconostoc souring can be controlled by treating the knives, harvesters, etc. with a suitable biocide like 'Bactrinol' (Sundara, 1998).
313
Sugarcane in agr icu l ture a n d industry
19.3.3 M e c h a n i s e d harvesting
L a b o u r h a s n o t o n l y become expensive but is not available in time. The cost of m a n u a l l a b o u r is Rs 1 0 0 - 1 3 0 per ton and it is even Rs 150 per ton in project a reas . H e n c e m e c h a n i s e d harvesting seems imminent in the near future. The chopp e r h a r v e s t e r s w e r e deve loped in Australia and the Australian cane combine is the m o s t w i d e l y u s e d s y s t e m . The combine harvester pushes the stalks, cuts them at t h e ba se i n t o p i e c e s or billets and an air blast removes the trash. The partially c l e a n e d a n d c h o p p e d c a n e is then dropped into a tractor drawn bin travelling by t h e s i d e of t h e c o m b i n e . Mechanized harvesting is carried out after burning the c a n e . Use of d e s i c c a n t s like gramaxone (1.5-3 1 ha-1) is suggested. But more rec e n t l y g r e e n c a n e h a r v e s t i n g has been carried out by modified combine harvesters . T h e fa l l en c a n e s are raised, and cut at the base by short, serrated knives.
1 he r o t a t i n g t w o b laded chopper knife cuts the cane into billets and an air blast r e m o v e s t h e d i r t a n d trash. This harvester has a 90-120 HP tractor to cut c a n e a n d t r a n s p o r t i t . For Indian conditions where holdings are small, tractors have t o b e m o d i f i e d .
At S a k t i S u g a r s mechan i sed cultivation of cane has been successfully attempted. M a n i c k a m ( 1 9 9 9 ) h a s detailed the mechanised cultivation of cane. It is claimed t h a t 1 0 , 0 0 0 a c r e s w e r e brought under this new method and it will reach 16,000 acres by t h e f o l l o w i n g year. In this system, all operations such as planting, weedi n g , f e r t i l i z a t i o n , b u n d l i n g and cutting are done mechanically. But the geometry of t h e p l a n t i n g h a s to be changed. In the new system cane is planted in paired row at 60—75 cm r o w s w i t h an area of 150 cm. The variety most suitable for this s y s t e m is Co 8 6 0 3 2 . S h o r t intercorps are taken in the skipped area. To harvest a p p r o x i m a t e l y 3 . 5 ha manually, one month is required but this combine harvester t akes j u s t h a l f a day . It has been estimated that to harvest 400 tons of cane, there is a n e e d of 5 d r i v e r s , o n e mechanic and one foreman. On the other hand, in the t r a d i t i o n a l m e t h o d of cut t ing 400 tons, nearly 6000 labourers are required ( M a n i c k a m , 1 9 9 9 ) . O t h e r advantages of mechanisation are steady and uninterr u p t e d s u p p l y of c a n e to the mill. The factory receives the fresh cane within one h o u r of c u t t i n g . T h i s a u t h o r is of the opinion that for totally mechanised cane c u l t u r e , s u i t a b l e va r i e t i e s with high tillering and less mortality are required. In the t r o p i c s n e a r e r t h e e q u a t o r , varieties like N C O 310 and N C O 376, N12, N14, e t c . a r e a d a p t e d to a w i d e spacing of 150 to 180 cm. The mechanised cultivation
314
19 Ripening, maturity and harvest
as adopted by Sakti Sugars will be watched with interest since the economic viability of this industry depends on reduced cost of production.
19.3.4 Post-harvest losses
For various reasons often the harvest cane is not crushed within 12 hours, and
staling takes place at the field/cane yard. The estimated losses under Indian condi
tions range from 50-150 tons/day if the harvested cane is supplied after 72 hours.
Besides, the loss in sucrose is to the extent of 25-30%. This author has observed
weight loss of 10-15% and sucrose loss of the same magnitude. In burnt cane, as
in South Gujarat, the sucrose loss could be to the extent of 40%. Efforts were
made by several investigators to control post-harvest losses by spraying water and
using a trash cover, spraying urea, etc. with little or no success. The losses depend
on climatic parameters, the method of harvest, and mode of transport. Hot and
dry weather increases both weight and sugar losses. Varieties are equally impor
tant and certain varieties have better sucrose keeping quality. CoC 671, stales less
and is less inclined to inversion or dextran formation, even after 14-16 months. It
is always advisable to supply fresh cane and provide minimum kill to mill delay.
But for unforeseen reasons, the delay in crushing varies from 3—10 days in India.
If the delay in crushing is anticipated, store the cane in small heaps with mini
mum ground contact or sprinkle with water plus potassium permanganate. The
cut ends lose moisture and bacterial growth takes place. The effective biocides
over cut cane are Bacterinol or a solution of potassium permanganate + sodium
metacilicate. Mr. V. M. Kulkarni of Pune (pers. comm.) has shown that sucroguard
is very effective in controlling the growth of microbes. The dosage for harvested
cane is 10 ml per ton of cane. In mechanized harvesting, due to the increased
surface urea of the small billets, the infection of Leuconostoc sp. is more pronounced.
The organisms associated with harvested cane are: Leuconostoc sp., Xanthomonas
sp., Flavobacter, Acetobacter sp., Actinomycetes, Streptomyces, etc.
Besides lowered sugar recovery, presence of dextran or other undesirable
polysaccharides reduces the export potential of sugar. According to Dr. S. Solo
mon (pers. comm.) the processes of Activated Inversion and Dextran Synthesis
(or AIDS syndrome) play a very detrimental role by converting sucrose into in
vert sugars, organic acids, ethanol, or dextran resulting in low and poor grade
sugar.
315
Sugarcane in agriculture and industry
Mill sanitation is equally important. The loss of sugar due to lack of mill sanitation is as high as 2.5 kg per ton of cane. But 1 kg per ton of cane can be retrieved by proper mill sanitation. Many microbes are associated with sugar processing. They are: Xantbomonas, Aerobacter, Leuconostoc, Aspergillus, Actinomycetes, Sac-charomyces, Bacillus, Clostridium, etc. The integrated mill sanitation approach consists of regular and thorough washing and steaming (70-95 °C), disinfection by chemicals prior to the start of crushing operations and good housekeeping. The chemicals used for mill sanitation are chlorine, formaldehyde, H 2 0 2 , quaternary ammonium compounds (Quats) and thiocarbamates. The chemicals used for mill sanitation are the biocides and they are preferably applied at the first and last mills. The cheapest and most commonly used biocide is Sodium-N Methyl-dithiocarbamate (30%). A cocktail of methyl and ethyl dithiocarbamate has been found useful the world over. Kilbact is equally effective as a biocide.
The economic benefits of applying organic sulphur based biocide kilbact in the milling tandem resulted in a saving of 1.14 kg sugar per ton of cane, which works out to 7 0 - 8 0 bags of extra sugar per day. The anticipated profit is around Rs 1 crore per season.
1 9 . 4
CANE FIRES
Cane fires are of frequent occurrence and late harvested cane in hot summer is prone to cane fire. T h e dried leaves and trash catch accidental fires from lighted cigarettes and bidis. Control is achieved by cutting the surrounding cane to isolate the fire or by back-firing, i.e. by burning the affected fields from leeward side which protect the fields further down wind (Blackburn, 1984). Fire can also be controlled by using tractor-drawn fire engines accompanied by mobile water tanks. In any case prevention is better dian cure. By and large insurance companies are reluctant to give adequate cover to the cane growers for losses sustained by fire. It is worth while to have a contingency fire fund from cess funds and cane taxation receipts.
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19 Ripening, maturity and harvest
317
Jaggery manufacture and allied products
Jaggery and khandasari (brown sugar) are important sweetening agents and they utilise about 45% of the cane produced. In the rural sector, this industry provides employment to 2.5 million people. The production of jaggery in India is 8.0 million tons and that of khandasari is 2.0 million tons. The consumption of jaggery is 15 kg per capita and has been stable for years. This product is supposed to be 'Health friendly since it has minerals like Ca, Fe, and P besides Reducing Sugars, (RS). Jaggery has a cooling and diuretic effect. It serves as a cardiac tonic, (Bangali Baboo and Solomon, 1995). An overview of the Indian sweetener industries is presented in Table 20.1.
The jaggery made at Mandya possessed an average sucrose of 82.25%, RS 4 .45% and ash 2.35%. The Net Rendement (NR) value is 69.54 which is classed as 'A' grade jaggery (excellent).
Net Rendement (NR) = Sucrose % - [RS% ± (3.5 x ash %)]
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20 Jaggery manufacture and allied products
Based on NR values, the grading of jaggery is as below.
NR values Grade Quality
>65 A1 Excellent
60-65 A2 Good
45-50 B Medium
<45 C Poor
The varieties suitable to jaggery making are given in Table 20.2.
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Sugarcane in agriculture and industry
The process of jaggery manufacture involves: (a) juice extraction, (b) juice boil
ing, (c) juice clarification, (d) evaporation and concentration, and (e) cooling and
moulding. Jaggery is made by farmers on a small scale using 3-5 rollers and open
pan evaporation. The extraction is barely 50-60% and the rest of the sugars are
burnt along with bagasse. A relatively better extraction is achieved through satu
rated crushing by using water or dilute juice. Bangali Baboo and Solomon (1995)
asserted that a small-scale maceration process and 6-9 hydraulic crushers can be
introduced to improve extraction. At present 4-roller bullock and power crushers
have been developed in Karnataka. The extracted juice is acidic in reaction
(pH 5-2-5.5) and is neutralised to 6.4 by liming. Generally 1 kg lime is mixed in
4 litres of water and 60-75 ml milk of lime would neutralise about 100 kg juice
(op. cit.). Liming improves consistency but excess liming should be avoided.
Juice boiling is done in open shallow iron pans (210-270 cm diameter and
45 cm deep). Fuel efficiency is very poor. Hence the development of bagasse gas-
ifiers to generate producer gas (methane) to concentrate juice appears promising.
A steady but slow boiling would permit the scum to appear on the surface. The
scum consists of colloidal matter, waxes, colouring substances, etc. The scum is
removed by a perforated wooden ladle. The vegetative clarificants in use are leaves
of Bhendi (Hibiscus esculentus), Castor, Deola (Hibiscus ftculeneus), Sukhlai (Kydia
calycina), Semul (Bambax mulbaricum), Phalsa (Grewia asiatica), Tapioca (Manihot
esculentus), Ambadi (Hibiscus canabinus), Groundnut, and Soyabean. The best
clarificant is the bhendi mucilage and the quantity is 45-50 g per quintal of juice.
The clarification makes the juice clear and light in colour. The chemical clarificants
are used to improve crystallisation, prevent charring and increase shelf-life. The
commonly used chemical clarificants are: lime, sodium hydrosulphite (Hydros),
sodium carbonate, sodium bicarbonate, super phosphate, alum, phosphoric acid,
citric acid, monocalcium phosphate or potassium metabisulphite.
After scum removal and clarification, the juice is boiled briskly at 105-108 °C
for about an hour. At this stage groundnut/castor/mustard oil is added at the rate
of 10—15 ml per pan (-150 litres of juice). This prevents frothing and the striking
point is achieved at 116-120 °C but the optimum seems to be 118 °C. At the
strike point the magma forms a silky thread when it is held in the air through the
wooden ladle. After the strike point, boiling is stopped and the magma is trans-
320
20 Jaggery manufacture and allied products
ferred to a cooling trough. The semisolid syrup is poured into moulds of various
sizes and shapes. The better moulds are the brick shaped ones weighing 125, 150,
or 500 g. Jaggery is hygroscopic due to the presence of fructose and glucose and
Na content adversely affects it. It is better to store jaggery in gunny bags placed at
an elevated position. Jaggery storage in polythene lined gunny bags seems to be
the best at 5 0 - 6 5 % RH. In recent studies, it was found by IISR that a gur drying
and storage bin of a quintal capacity is suitable for jaggery storage in humid con
ditions. Polyethylene bags are equally effective in storing jaggery. Regarding the
mold size, small buckets of 1 and 2 kg are superior in keeping quality. Brick
shaped jaggery molds of 1 or 2 kg have better storability than round shaped (Golas)
ones (Plate 20.1). The standard requirements of good jaggery are presented in
Table 20.3.
321
Cream jaggery is made by adding 1% activated carbon after the initial scum
removal. The juice is heated for some time and then passed through a bed of
activated carbon and sand. The juice is further boiled with a small quantity of
milk and chemical clarificants. Cream jaggery is light golden yellow in colour
with excellent consistency and has good export potential.
Some technological, social, economic factors of jaggery vs sugar are presented
in Table 20.4. By any standard, jaggery is preferred for health reasons over sugar.
20 Jaggery manufacture and allied products
20 .1
ALLIED PRODUCTS
20.1.1 Khandasari
Khandasari or brown sugar is obtained from sugarcane juice by the open pan
process. It is mostly in coarse powder form and is chiefly used in making sweetmeats.
20.1.2 Liquid jaggery [Kaakavi /Kakumbi/ Golnupa)
Liquid jaggery is an intermediate product obtained during jaggery making. This contains water, sugars, and non-sugars (Wandre and Hasabnis, 1995). Fructose and glucose are in equal proportions, with proteins, organic acids, and minerals. The well-mature canes of Co 740, Co 419, Co 7219, Co 8014, CoC 671, and Co 775 are well-suited for making liquid jaggery. After the juice is extracted, potassium alum crystals are dipped in it for half an hour. This facilitates sedimentation of solid particles. The liquid is the decanted to the storage tank. The clear juice is poured into a boiling pan. About 50 g of lime is added to bring the pH to 6.0. Bhendi mucilage is added and the first scum is removed when the temperature is 85 °C. Chemical clarificants include phosphoric acid and super phosphate. Boiling is continued and the second scum is removed at 98 °C. The strike point is 106 °C and at this stage the pan is removed and 0.04% of citric acid is added. Liquid jaggery is sweeter than cane sugar and jaggery. After complete settling, liquid jaggery is filled in clean and sterilized bottles. This can be stored for 1-1½º years. It is necessary to add 0 .1% citric acid and 0 .1% sodium metabisulphite for better preservation.
20.1.3 Rab
This is a semi-liquid form of jaggery obtained by concentrating juice to lower brix. It is stored in earthen pitchers. On storage crystals will develop. These crystals are used in rural areas as sweeteners.
20.1.4 Bura
It is produced by recrystallisation of any kind of sugar or khandasari sugar and
then made into a fine, free-flowing product. It is a sweetening agent.
323
Sugarcane in agriculture and industry
20.1.5 Misri
This is a product made by recrystallisation of sugar. In fact it is a conglomeration
of sugar crystals of irregular size and shape. It is chiefly used as 'Prasada'.
20.1.6 Shakkar
This is brownish in colour and is a powdered 'Gur' after concentrating sugarcane
juice to higher brix. It is a sweetening agent and is easy to dry with easy packaging,
handling, and transport.
20.2
PRESERVATION OF SUGARCANE JUICE
Attempts were made since early times to preserve sugarcane juice in a readily available form in bottles. But it gets sour due to microbial attack. The extracted juice is pasteurized for 10 min at 80 °C. To improve the taste, juice is blended with 0.3% lemon and ginger (0.1%). Pasteurization and processing arrest the growth of Leuconosta sp. A preservative like potassium metaphosphate is added at 70 ppm. The clear juice is bottled and sterilized for 30 min. This can be stored for about 6 months.
20.3
HIGH FRUCTOSE SYRUP (HFS)
HFS contains 70 to 90% fructose with a Sweetener Index (SI) 1.8 times sweeter than cane sugar. Besides being sweeter, it has a pleasant flavour, is less hygroscopic, and has fewer calories. Initially it was made from corn starch, and was known as High Fructose Corn Syrup (HFCS). Starch from potato/tapioca can also be used to make high fructose syrup. Basically, HFCS is used extensively in the soft drink and food industries. Its alarming increased usage in the soft drink industry has replaced more than 10% of the sugar market. By 1997, 100 million tons of HFCS had been used in the soft drink industry. Recently attempts have been made to produce High Fructose Syrup (HFS) from cane molasses using the enzyme glucose isomerase isolated from Bacillus steriothermophilus. The latest technology includes ultra filtration to obtain ultra high fructose glucose syrup.
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20 Jaggery manufacture and allied products
2 0 . 4
NUTRIENT SWEETENERS FROM CANE SUGAR
Artificial sweeteners like saccharin, aspartame, and acesulfam-K have already been alluded to in the previous chapters. Different sweeteners have been developed to meet the requirements of sophistication and changes in lifestyles. A broad categorization of different sugars is presented by a flow diagram (Fig. 20.1).
Among the special sweeteners, sucralose is marketed along with 'Splenda' as its brand name. Sucralose is superior to Nutrasweet, due to longer shelf-life and is thermostable during cooking. It contains no calories. Palatinit is developed by a special process of converting sucrose and is used in chocolate bars, chewing gums, etc. Isomaltulose is a stable reducing disaccharide with half the sweetener index (0.5) of sucrose. It is also known as palatinose. This is produced from sucrose by employing the immobilised enzyme of Protaminobacter rubrum. Palatinose finds extensive usage in the confectionery industry. Neosugar is produced by microbial conversion of sucrose and its sweetener index is 0.2. It is a noncarcinogenic and a noncalorific sugar, and is hence suitable for diabetics.
Alditol sweeteners are sugar alcohols. Xylitol (Xalitol) is a white crystalline powder found in fruits and vegetables. Sugarcane bagasse is rich in Xylan which is isolated and hydrolised to xylose. Hydrogenation of xylose gives Xylitol. It is non-carcinogenic and does not cause dental caries. Lactitol is obtained from milk sugar and its SI is 0.33. It does not affect teeth and its calorific value is 2.4 Kcal g -1. Different types of alcohol sugars are used in beverages, canned fruits, and bakery products.
Protein sweeteners are not considered safe for human consumption. Miraculin is a glycoprotein with high molecular weight. However, Thaumatin is included in the chewing gum.
Among the artificial sweeteners, saccharin is the oldest but it leaves a bitter
aftertaste. It is carcinogenic in nature and its consumption is not encouraged.
Acesulfame-K has replaced saccharin. Aspartame can be made from fumaric acid
using the strains of E.coli with high aspartase activity. Due to its synergistic effect
with fruit flavours, it is commonly used in desserts.
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20 Jaggery manufacture and allied products
Steviosides or Steviron are the noncalorific sugars obtained from the leaves of
Stevia rebaudiana. This is a native of Paraguay and these sweeteners are extensively
used in Japan. The leaves of Stevia contain 12% sugar by weight and steviosides
are diterpene glycosides. High yielding varieties of Stevia are cultivated in Japan.
At the Agricultural University, GKVK, Bangalore, efforts made to establish Stevia
plants have met with partial success.
HFS is of great commercial value and is generally prepared from corn. In re
cent times, attempts have been made to produce HFS from sugacane molasses
using the enzyme glucose isomerase isolated from Bacillus steriothermophilus. HFS
is mostly used in the soft drink industry and its usage is increasing.
327
Box I
Liquid Jaggery
• Liquid jaggery (Kaakavi or Kakumbi) is an intermediate product
in jaggery manufacture and is collected in semi-liquid form from
the boiling pan and packed in suitable containers,
• The striking temperature is 106 °C.
• Use of 0.04% citric acid is found beneficial in minimising crystal
lization and for improving the colour.
• Use of 0.1% potassium metabisulphite or 0.5% benzoic acid im
proves keeping quality as it acts as a preservative.
• The suitable varieties are CoC 671, Co 8014, Co 7219 and
CoM 88121.
• The following is the typical chemical composition of liquid jaggery.
Water 30-35%
Sucrose 40-60%
Invert sugar 15—25%
(mainly dextrose and levulose)
Calcium 0.3%
Iron 8.5-11.0 mg 100 g-1
Phosphorus 3.0 mg 100 g-1
Protein 0.10 mg 100 g-1
Vitamin B 14.0 μg 100 g-1
Sugarcane in agriculture and industry
Figure 20.2 gives the flowchart for the manufacture of liquid jaggery.
Fig. 20 .2 Process flowchart for manufacturing liquid jaggery
328
20 Jaggery manufacture and allied products
329
By-products of the sugar industry: recent trends
Sugarcane has come a long way from being a closely managed garden crop in the Vedic times to becoming an important commercial crop of the tropics and subtropics. But it has had a roller-coaster ride and has witnessed the best of times and the worst of times (Alexander, 1993). No other plant can convert so much radiant energy into calorific energy on behalf of so many people. It is unmatched in the plant kingdom for its twilight photosynthesis (pre-sunrise and pre-sunset). It is a complete physiological system, a sugar system, an energy system and an environmental system. Verily it is a renewable, natural, agricultural resource (Hunsigi and Singlachar, 1994).
21.1
ENVIRONMENTAL SYSTEM
It is ecofriendly, alters the microclimate, reduces atmospheric CO2 and pollutants and enhances O2. Perhaps sugarcane is one field crop which under high density plantation possibly reduces the greenhouse effect.
2 1 . 2
PRODUCTION SYSTEM
It has excellent anatomical and physiological features with a Kranz syndrome. Besides the C4 pathway, high photosynthetic rates are due to greater leaf thickness, width, porosity, specific leaf weight, LAD and LAI. The photosynthetic mobiiity is high in the long internodes which serve as powerful Vehicles' for sugar storage. With no product repression, the theoretical maximum yield is 129 g m - 2 d-1
or 470 t ha-3 yr- l, The dry matter yield is approximately 80-100 t ha-1 in the tropics, which is unmatched by any agricultural crop. For the record, India produced 16.5 million tons of crystal sugar, 8 million tons of jaggery and 2 million tons of khandasari during 1996—97.
2 1 . 3
ECONOMIC SYSTEM
It is regarded as the sixth largest crop commodity in the world: Wheat > Corn > Rice > Barley > Soyabean > Sugarcane > Oats > other food crops. Every calorie
330
21 By-products of the sugar industry: recent trends
invested in sugarcane production results in regeneration of 6-12 calories. Globally it is valued at US$ 143 billion. In India, it is worth Rs.500 crores. Sugar complexes employ over 4 lakh technically skilled people and there are 30—40 lakh growers in the rural sector. It is a source of livelihood for nearly 7% of the country's population.
This plant has been so far regarded as a monolithic crop (sugar crop). But it deserves a niche as a multi-product commodity providing food, fuel, fibre and fertilizer. The crop is a source of at least 38 by-products and co-products having a net value of US$ 8000 per ton of raw material (Paturau, 1986). A schematic diagram of major by-products of the sugar industry is shown in Fig 21.1. As a first approximation, 100 tons of cane crushed will yield the following (Table 21.1). The by-product availability in India and the world is given in Table 21.2.
T a b l e 2 1 . 1 Products formed from 100 tons cane crushed
— 10 tons sugar
— 4 tons molasses
— 3 tons filter mud
— 0.3 tons furnace ash .
120 tons flue gases (180 °C)
— 30 tons bagasse (26 tons captive fuel, 4 tons surplus)
— 150 kwh surplus electricity
Table 21.2
By-products
Bagasse
Press mud
Molasses
Cane tops
Refined wax
By-pi •oduct availability in India
Availability in the
world (million tons)
150
16
18
130
380 kg per 1000 tons
of cane crushed
and the world (1997-98)
Availability in
India (million tons)
52
5
6.9
75
—
Source: Zende, 1995.
331
Sugarcane in agriculture and industry
Press mud
Fertiliser, Animal feed, Cane
Lignin
Ligno sulphate
Flue gases
Trash
Cane tops/ leaves
Fodder, Leaf protein
Furnace ash
Glass industry
Allied products
Jaggery, Khandasa Liquid jaggery
1 Distillery effluents
wax
i,
Fertiliser, Biogas, Potash
Fig. 2 1 . 1 Major by-products of the sugar industry
332
21 By-products of the sugar industry: recent trends
2 1 . 4
FIBRE CANE SYSTEM
The physiology of cane is such that it produces a high biomass and compares with many fast growing trees. Nearly 30% of the biomass in sugarcane constitutes bagasse or megasse which comes as a residue of sugarcane after it is crushed in the mills. The mill wet bagasse has nearly 50% moisture with 4 6 - 5 2 % fibre. Fibre means all insoluble solids—fibrous or not (Meade and Chen, 1977). The conservation of bagasse is of great importance. It can be used as house boiler fuel and in other co-products. The bone-dry bagasse has the following composition.
Cellulose 45 .0%
Pentosans 28 .0%
Lignin 20.0%
Ash 2.0%
Sugar 5.0%
The cellulose content of bagasse is used in fibre-based industries. The rind
portion yields high quality cellulose. The inner portion of bagasse is pith which is
non-fibrous in nature but has a calorific value similar to that of bagasse. Pith is a
source of fuel and/or fertilizer. The pentosan content of bagasse is used in the
manufacture of furfural. The lignin content can be used for the manufacture of
chemicals such as sucrolin.
T h e global p roduc t ion of bagasse is 150 mill ion tons ; in India it is
52 million tons. With a modest 10% saving of bagasse, 15 million tons and
5.2 million tons of bagasse will be available in the world and India respectively
for making bagasse-based products. Nearly 7 tons of mill wet bagasse makes 1 ton
of bleached pulp. Based on the above 10% saving of bagasse, 2.14 and 0.74 mil
lion tons of quality bleached bagasse pulp will be available in the world and India
respectively.
21.4.1 Factors affect ing fibre in cane
Fibre accumulation in cane starts from 3 months and continues to increase as age
advances. On an average, commercial hybrids contain fibre content in the range
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Sugarcane in agriculture and industry
of 13.5 to 16.0%. The late harvested crop is more fibrous. Ratoons tend to have
more fibre than the virgin crop. Drought conditions lead to increased fibre but
there is a higher content of non-fibrous pith. Narrower spacing of 0.5 m nearly
doubles the fibre content as compared to wider spacing of 1.5 m. Lodged cane has
less fibre. Other factors which influence fibre in cane are nutrition, cultural and
irrigation practices. Late and heavy N application coupled with excessive irrigation
reduces both fibre and pol. These conditions favour 'pithiness' or 'piping'. It is
reasonable to suggest that a balanced carbohydrate—N relation is essential to
accumulate both sugar and fibre in cane. Both minor and secondary elements
have no significant influence on fibre accumulation. However, the role of silicon
(Si+4), a beneficial element, is intriguing. Experiments with ripeners like sodium
metasilicate (as source of Si) have amply demonstrated an improvement in pol
with no significant effect on fibre. Potassium has a strong influence in flushing
out both tissue moisture and nitrogen. In fact tissue moisture has to be reduced to
improve both fibre content and sugar. Alexander (1973) states that K addition
improves fibre content by reducing tissue moisture and increases pol per cent of
cane by converting reducing sugars to recoverable sugars. Humbert (1975)
suggested late and heavy K application for maximum production of sugars and
cellulose and recommended an N P K ratio of 2 : 1 : 4 to achieve higher sugar and
fibre production.
A direct relation exists between sugar, fibre, and moisture and maximum sugar
accumulation should not be at the expense of fibre build-up. Further, tissue mois
ture is more closely related to fibre than to sugar. A negative relation exists be
tween moisture and fibre, and moisture and sugar. Clements (1980) provides
evidence that sheath moisture, (3-6 leaf sheaths) an index of tissue moisture and
physiological activity of plants, can be kept as low as 68-69%. The recent tech
nique of ripening involves continued build-up of dry matter (half of which is
sucrose and the other half fibre) and the biological pathway should be chosen so
as to increase sucrose and lignocellulose at the expense of tissue moisture but
without killing the plant.
21.4.2 Role of varieties
Fibre in cane is of structural importance. Among the Saccharum spp. spontaneums
and robustums contain more fibre than the offlcinarums. The allied genera Mis-
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21 By-products of the sugar industry: recent trends
canthus has the highest fibre content of over 5 1 % . Varietal differences also exist with regard to fibre content. The popular cultivars such as Co 421 , Co 413, Co 426, Co 7219 and Co 6806 have more fibre than Co 419 and Co 740. N C O 376 has more fibre than N C O 310. It is interesting to note that early rich canes such as CoC 6 7 1 , Co 997, Co A 7701, Q 49 and B 37172 possess high fibre and sugar contents. This confirms the contention that sugar and fibre are not incompatible. Recently released varieties such as Co 7804, Co 8021, Co 8371 and Co 86032 are endowed with high sugar and fibre contents. Flowered cane has more fibre than the non-flowered ones. Higher the fibre and silicon contents, less is the infestation of borers.
Concerted efforts were made at the Sugarcane Breeding Institute, Coimbatore (SBI) to develop varieties which contain high fibre and sugar. Indo-American varieties or IA clones were best suited for this purpose. The IA clones are the first or second nobilization products developed at the Sugarcane Breeding Institute, Coimbatore involving wild robustums and Puerto Rican/Hawaiian varieties (Naidu, 1986). High sugared and fibred varieties developed at SBI, Coimbatore are presented in Table 21.3.
T a b l e 2 1 . 3 Indo-American clones with high fibre and sugar contents
Clone No.
Co 7314
G340
G335
G375
G504
G415 G330
G338
G354
Fibre %
18.02
18.06
18.45 18.90
19.41
19.62
20.16
20.00
20.42
Sucrose %
19.17
19.08
19.80
19.95 20.46
21.86
20.30
19.59 18.06
Source: Naidu, 1986.
Among the IA clones tested, the most promising ones are G 354 and G 330
with high fibre and sugar contents.
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Sugarcane in agriculture and industry
21.4.3 Bagasse storage
Due to the seasonal nature of cane cultivation, storage is essential for pulping. Handling and storage costs are high as loose bagasse is porous and bulky. The bulk density ranges from 120—180 kg m-3 and mill wet bagasse has 5 0 % moisture with 2 - 3 % residual sugar. While in storage, a combination of high temperature and acidity results in hydrolysis of cellulose with reduced pentosans, hemicellu-lose and a consequent lowered pulp yield. Atchison (1986) stressed that the economic feasibility of utilizing bagasse rests on proper storage and effective depithing (pith removal). Pith constitutes about 25-30% of dry bagasse. It is non-fibrous and has 9 3 % of the calorific value of whole bagasse. A rough estimate show that 2 t moist pith is equivalent to 1 t coal as fuel. Thus pith can be conveniently used in boilers and special furnaces. Rydholm (1965) has stressed the importance of depithing for it gives higher pulp yield, brightness, tensile strength, and burst and tear factors with reduced kappa number. (Kappa no. (K) is a measure of chemical consumption in making paper.)
There are 3 types of depithing (i) dry depithing (ii) moist depithing (iii) wet depithing. Dry depithing is ruled out as it causes serious dust pollution and wear and tear of the mills. Hence two stage depithing is advocated. This is moist depithing at the sugar mill and wet depithing at the paper mills.
Bagasse storage is better achieved by stacking it in bales of 125 kg each with 50% moisture. The bales are stacked in a pyramidal shape with enough space between them for aeration. The stacked bagasse is treated with bactericides such as S 0 2 , formaldehyde, Na 2 C0 3 , etc. Efficient bagasse storage is possible by retarding the activity of cellulolytic microbes. This is achieved by creating an acidic (pH 4), aerobic environment with proliferation of Lactobacilli. A biological liquor consisting of seed Lactobacilli is employed to impregnate the stored bagasse. Thus the general principle to conserve stored bagasse is to create an acidic, aerobic environment with proliferation of Lactobacilli.
Lignin protects the cellulose strands. But lignin in pulp gives undesirable colour to the paper besides increasing the consumption of chemicals. Delignification is achieved by employing a particular strain of fungus which attacks only the pith and lignin while protecting the cellulose. Guetierrez et al. (1986) in Cuba demonstrated that white rot fungus {Phanerocheate chrysporium, K3) selectively delignifies bagasse and the strain 85118-6 was the most efficient delignifier. A suggestion is
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21 By-products of the sugar industry: recent trends
mooted that a 'microbial consortium' may achieve the desired delignification of bagasse.
21.4 .4 Biodegradation of bagasse
The biodegradation of bagasse has been thoroughly studied. Bagasse has residual sugar content (- 2.5%) and a high moisture content which accelerate the fermentation process. The darkening of bagasse occurs because of fungus growth. Furthermore, a combination of high temperatures and acidity results in hydrolysis of cellulose with a consequent reduction in pulp yield. An exposed larger surface area, heterogeneity of fibres in bagasse and tropical conditions favour microbial growth and colonization. Rotten bagasse has a microbial population of 5 x 108 g -1 .
The sequence of processes involved in bagasse biodegradation is shown in Fig. 21.2. Biodegradation of bagasse results in a reduction in pentosan and hemicellulose contents and a loss of fibre properties .
Fresh bagasse organisms and by-products
Fig. 2 1 . 2 Biodegradation of bagasse
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Sugarcane in agriculcure and industry
21.4.5 Development of wet-pile technology
This is essentially the Ritter process, developed by E. A. Ritter, and involves the impregnation of moist or wet, depithed bagasse with a biological liquor. T h e seed Lactobacilli culture is employed and the organisms are encouraged to multiply by the addition of nutrient media and molasses.
It was observed that fibre preservation was more effective in depithed bagasse than in whole bagasse since the former has less sugar.
Thus, bagasse stored in a bioliquor has a higher pulp yield and lower consumption of chemicals (i.e. a lower kappa number) and also has better colour and fibre properties.
The storage of bagasse, as advocated by Dr. Cusi, is a simple system where baled bagasse is stored in ventilated stacks with sufficient air space. The pith cells present in the whole bagasse protect the cellulose and the moisture content drops from 50% to 30 -35% in about 50 days. However, there are certain limitations to this method under tropical conditions due to the higher ambient temperatures.
21.4.6 Bagasse for paper making
The production of paper from bagasse dates back to 1838 but significant developments were made around 1910 in countries like Brazil, Cuba, West Indies and Hawaii (Singh and Solomon, 1995). It was only in 1950 that the technology of bagasse pulping was perfected and all grades of paper such as tissue, toweling, cultural paper, etc. were made from bagasse. The global production of bagasse pulp is estimated at 2.5 m tons.
The heterogenous character of bagasse fibres needs to be reckoned with and they are difficult to pulp mechanically. They are comparable to hard woods like Eucalyptus. The fibre length (1) varies from 0.56 to 2.87 mm with a diameter (d) of 0.012 to 0.050 mm. The average 1/d ratio is 52.2 (Table 21.4). The pulp yield is relatively less than in hard woods but the high pentosans and low lignin content offer better strength properties. Obviously they provide higher burst and tear factors and breaking length.
21.4.7 Bagasse newsprint (BNP)
Bagasse newsprint has come of age and more than 140 years of research has gone in since the early attempts in 1856 by Henry Low of Baltimore, USA.
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21 By-products of the sugar industry: recent trends
Table 2 1 . 4 Proximate analysis, fibre properties and pulp yield of sugarcane bagasse and Eucalyptus hybrid
Newsprint is a low grade and low priced sheet but should withstand the re
quirements of high speed printing presses besides having high opacity and oil
absorbency. FAO specifications for newsprint are:
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Sugarcane in agriculture and industry
Tear factor 46
Opacity (%) 86
Brightness (% MgO) 50
Grammage (g m-2) 48.8
The per capita consumption of newsprint in India is 0.5 kg as against the world average of 5.6 kg. Conventionally, newsprint is manufactured with 8 5 - 9 0 % soft wood mechanical pulp and 5-15% soft wood chemical pulp. There is no rigid definition for BNP but it should contain over 60% bagasse pu lp . Atchison (1986) has suggested three cardinal points for BNP. (i) Moist and wet depithing to remove maximum pith. (ii) Good storage to prevent excessive loss in fibre properties. (iii) A high proportion of mechanical pulp in fibrous furnish.
This author has demonstrated that 80% bagasse pulp can be blended with 20% long fibre Kenaf/Mesta (Hibiscus sabdariffa or H. cannabinus) to produce an acceptable grade of newsprint. The future newsprint furnish aims to totally dispense with long-fibred chemical pulp and additives.
There are about 300 paper and paper board mills in India as sugar paper complexes. The installed capacity is 30 lakh tons paper per annum but the production is only 20 lakh tons. The newsprint production is only 3 lakh tons but the demand is 6 lakh tons—a yawning gap of 3 lakh tons per year.
To wrap up, sugarcane bagasse is the future fibre of the tropics and subtropics for pulp and paper making. Cane cultivars need to be developed to maximize both sugar and fibre content. Agro-techniques like irrigation, manuring and plant density need to be adjusted to ensure low tissue moisture but high sugar and fibre content.
21.4.8 Agglomerated products of bagasse
I he agglomerated products of sugarcane bagasse include particle boards, fibre boards, insulation boards and moulded products. Particle board is a sheet material manufactured from small pieces of lignocellulose materials, agglomerated by use of an organic binder with one or more of the following agents: heat, pressure, humidity and catalyst (Somani and Grewal, 1995). About 3 tons of mill wet bagasse is required to produce 1 ton of particle board. Synthetic resins such as phe
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21 By-products of the sugar industry: recent trends
nol-formaldehyde and urea formaldehyde are required as binding agents. Particle boards can be classified as low density (insulating type), medium density and high density (hard board type). The physical properties of boards made from bagasse are: thickness 16 mm, density 639 kg cm - 3 , bending strength 199 kg cm - 3 , internal bond 8.2 kg cm - 2 and swelling (after 24 hr) 5.8%. Particle boards are used for making partitions/panels, furniture, false ceiling, table top, etc. Essentially the particle boards, fibre boards, etc. from sugarcane bagasse would replace natural wood resources which are used for making plywood.
Hbre boards are sheet materials of varying densities manufactured from refined or partially refined wood fibres or other vegetable fibres (op. cit.). These are interlaced fibres of lignocellulose materials with great strength and resistance to moisture, fire or decay. Fibre boards are of three kinds—low, medium and high density boards used as insulation boards or panel boards or for construction purposes. Bagasse cement boards are high density boards (1250 ± 50 kg m-3) and are used extensively in the construction industry: The molded products from bagasse are the articles made with thin ligno-cellulosic material with hot press organic binders in moulds of different shapes. The moulded particle boards are used in cabinets for radios, televisions, kitchen furniture, table tops, suit cases, ceilings, plank boxes, coffins, etc.
21.4.9 Other products of bagasse
Bagasse briquettes or bagasse logs are used as fuel in brick kilns or as domestic fuel
for cooking. The production of bagasse charcoal is more promising. The prepara
tion of charcoal briquettes from bagasse involves carbonization, mixing of molas
ses and final carbonization of briquettes. Producer gas from bagasse consists of
C O 2 , C O , C H 3 , and N 2 . The calorific value is 5000 KJ/kg but it has many disad
vantages.
Bagasse ash is produced at 0 .3% per ton of cane crushed. If a factory crushes 3
lakh tons in a season, it has to handle about 1000 tons of fly ash. Ash is normally
spread in the field since it is rich in SiO2 , Fe, P, K, and lime. This author has
shown that ash can be mixed (1/10 to 1/20 by wt basis) in press mud plus rock
phosphate along with microbes. The product is called 'phospho-green' and is an
excellent source of fertilizer for many field and horticultural crops. In Mauritius
and Egypt, ash is used in the manufacture of glass.
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Sugarcane in agriculture and industry
Zende (1995) has reported that bagasse can be used as poultry litter, mulch
and soil conditioner. In Australia, Mauritius, and Hawaii bagasse at the rate of
12.5 r ha -1 has been used as a soil conditioner to resist soil erosion and improve
soil properties. In North America, dehydrated fresh bagasse was used as soil mulch
to reduce erosion and increase soil moisture retention. It is however incongruous
to use bagasse as a soil conditioner since many value added products can be ob
tained from it. Cultivation of edible mushrooms on bagasse is a profitable proposition. Ba
gasse is rich in cellulose, and hemi-celluloses and it serves as an excellent substrate for edible mushrooms (Pleurotus ostreatiis, P. sajor-caju, P. citrino-pileatus). C o m mercial cultivation of mushrooms on bagasse gives rich proteins in rural areas. It has been observed that mushrooms grow better on bagasse than other materials such as paddy/wheat straw.
Green tops and bagasse are a good source of fodder and feed. India has a large livestock population of over 500 million heads. During years of drought in m a n y parts of India bagasse serves as a buffer feed. Due to the lignin content of bagasse, it needs pre-hydrelysis treatment. Predigested bagasse is mixed with millets, corn, oil cakes and urea to improve its digestibility and nutritive value. Predigestion is done at a high temperature and pressure, and molasses is added. Such a feed is known as bago-molasses. Nearly 45% bagasse is mixed with 25% final molasses to obain an acceptable grade of cattle feed. These feeds are popular in Latin America. Cane separation technology has opened new vistas where the rind po r tion is used for fibre making and the pith with mixed additives is used to make 'Camfith'—a cattle feed. Many sugarcane based feeds such as Solicana (sundried crushed cane) and Saccharine (treated crushed cane) are popular in Cuba a n d many Caribbean countries (Singh and Solomon, 1995). Hydrolysed pith is obtained by treating the pith with steam and used as animal feed together with supplements. It is also a good poultry feed. Cuba produces nearly 15 types of cattle feed after steam treatment, which serves as roughage.
Sugarcane trash is an important biomass, a co-product of the sugar industry. In situ conservation of trash is an essential prerequisite of organic sugarcane. And
trash burning should be totally dispensed with. Raking and aligning of trash in cane rows is effective in controlling weeds and soil moisture conservation. Zende
(1995) advocated that burying trash in soil improves C and N status, overcomes
342
343
21 By-products of the sugar industry: recent trends
the ill effects of soil compaction and allows optimal air and moisture relationship
in the rhizosphere.
Approximately 8-10 t ha -1 of trash is left over in the field. Besides, 8-9 tons of
stubbles and 4-6 tons of roots per ha are produced. A rough estimate shows that
nearly 40 million tons of trash is produced annually which can be gainfully em
ployed in cane cultivation. The chemical composition of sugarcane trash is pre
sented in Table 21.5. The water insoluble fraction of trash comprises cellulose,
hemicellulose and lignin. Hence decomposition of trash takes a longer time. Cer
tain fungi/bacteria and actinomycetes are known to enhance trash decomposi
tion. Even the addition of FYM, press mud, poultry or sheep manure hastens the
decomposition of trash.
Table 2 1 . 5 Chemical composition of sugarcane trash
Source: Mohan Singh, 1995.
Sugarcane in agriculture and industry
Our experiments have shown that spreading cowdung slurry is ideal in hasten
ing trash decomposition. Polyphenols and lignin not only hinder decomposition
but also leave allelochemicals which substantially reduce stubble sprouting and possibly reduce the yield of ratoon cane. The microbes involved in the decomposition or trash are furnished in Table. 21.6.
344
Ethanol production from cellulosic materials such as bagasse and CTL is exciting and is succinctly described by Hunsigi (1993a). Hydrolysis of cellulose can be accomplished by the enzyme cellulase. The mutant strains ot Clostridium sp. are efficient converters of cellulose/hemicellulose to ethanol. Enzymes secreted by Trichoderma reesei are equally effective in the conversion of cellulose to ethanol. High costs are involved in making biofuels from cellulosic material and hence such biofuels are not competitive with the ones produced from fermentable solids.
Source: Singh and Solomon, 1995.
Box I
Cane Tops and Leaves (CTL)
CTL serve as the best green fodder, particularly in summer months. This can also be ensiled with molasses (5-10%) and ammonia (0.2%). Acetic acid is produced during fermentation which improves the keeping quality of the ensilaged material. CTL can also be mixed with urea, cornmeal bagasse pith, oil cakes, etc. to improve their nutritive value. The global production of CTL is estimated at 300 million tons annually and it is an important biomass to produce value added products such as Leaf Protein (LP), Single Cell Protein (SCP) and Dehydrated Sugarcane Top Production (DSCT). Ethanol and energy generation is possible through CTL.
21 By-products of the sugar industry: recent trends
Table 2 1 . 6 Microbes involved in the decomposition of trash
Source: Zende, 1995.
Among the microbes, Aspergillus flavipus took 3 months to decompose the
trash, which was followed by a mixture of culture and Trichoderma viridae. It is
now well recognised that a consortium of cellulolytic bacteria and diazotrophs
would increase trash decomposition and also cause higher N2 fixation. Other
genera involved in trash decomposition are Helminthosporium, Fusarium and
Cladosporium. Several diazotrophs are also involved in the decomposition of trash.
But Azospirillum brasilense plays a prominent role in the N2 fixation during trash
decomposition. High nitrogenase activity in trash was observed at high O2 con
centration and low moisture content in trash. It is supposed that microaerophilic
conditions must have been created around Azospirillum brasilense, thus providing
a conducive environment for N2 fixation.
Cane yields have almost invariably improved following trash management. The
ideal management protocol is that trash at 5 tons ha - 1 may be buried in the soil
and 5 tons ha - 1 placed on the surface along with the cultures of Trichoderma
viridae and Azospirillum. This will enhance both decomposition and N2 fixation.
The beneficial effect of trash management was observed in first and second ratoons.
Value added chemicals from bagasse include furfural, furfuryl alcohol,
alfacellulose, Xylitol and Sucrolin. Furfural is a highly valued chemical used as a
solvent in many industries. It is a colourless, inflammable, volatile, aromatic, red
dish liquid. It can be manufactured from rice husk, groundnut shells, corn cobs,
etc. but bagasse is a cheap source to manufacture furfural. India produces about
345
Sugarcane in agriculture and industry
3500 tons of furfural per annum. It is used as a selective solvent for refining lubricating oils, vegetable oils, paints and varnishes. It is also used for making synthetic resins, nylon 6-6 and butadiene. Furfuryl alcohol is produced by the catalytic hydrogenation of furfural. It is mainly used in the production of furan resins, utilized as a binder in the casting industry.
Highly purified cellulose (85% cellulose) is known as alfacellulose and used in the manufacture of rayon, cellophane, explosives, photographic films and extremely fine paper. Alfacellulose is also called dissolving pulp.
Xylitol is obtained by the high pressure hydrogenation of xylose and bagasse containing pentosans mainly composed of xylan and araban. Xylitol is used in chewing gums and bakery products.
Sacrolin is obtained when bagasse is auto-hydrolysed to furfural. This is a soluble lignite and is employed as a release agent in casting foundries.
Activated carbon is produced when bagasse is pyrolized for 20 hours at 450 °C devoid of atmospheric air. It is a decolouring agent and is used to refine sugar, oils, fats, beverages and spirits. Activated carbon is used for making cream jaggery which has a high export value.
Hydrolysed pith is obtained by treating pith with steam. This improves digestibility of the feeds and serves as excellent roughage for ruminants, poultry and geese. Bagasse pith can be used directly for animal feeding after blending with urea and molasses solution. Pith can also be utilized for microbial protein production. It has been possible to produce protein by the action of Trichoderma reesei Qm 9414 on pith.
2 1 . 5
ENERGY CANE SYSTEM
The energy cane is neither a botanical concept nor a cultivar. It is a management concept where anatomical, physiological and agronomic features are tailored towards growth. The agronomy of energy cane includes closer spacing (0.3 to 0.45 m) , high rate of N fertilization (450-500 kg ha -1), and late application of N (8 -9 months stage). The distinct feature of energy cane is its 'invasiveness' or 'weediness'. Other features are early canopy closure, expansive leaf canopy, tillering propensity, active crown leaves, extended root proliferation of surface and subsurface root system, sustained ratoonability and high tonnage. Other advantages of en
346
21 By-products of the sugar industry: recent trends
ergy cane are biological weed control through luxuriant green foliage, greater leaf area duration and protection from erosion and soil compaction. It is suggested that in energy cane, high rates of inversion and loss of 2 -3 units in NR is more than compensated by the gain in biomass. An ideotype of energy cane is presented in Fig. 21.3.
Fig. 2 1 . 3 An ideotype of energy cane (Alexander, 1985)
The promising energy cane cultivats are N C O 310, PR 8 0 - 8 - 2 , PR 980,
CP 65-357, CO 62175, B 37172 and B 70-701 . The most promising one is
347
Sugarcane in agriculture and industry
US 67-22—2 of S. spontaneum. These cultigens like CP 65-35/ and US 6 7 - 2 2 - 2
have given as much as 10,000 litres ethanol ha -1. But we have obtained 6 0 0 0 -
8000 litres ha"1 ethanol (Cv. CO 627175) as against sweet sorghum which has
given 2000 litres ha -1. Performance of some energy canes is presented in Table 21.7.
Among them EP 18 and EP 30 seem to be promising, having yielded 5.0 t ha-1
of ethyl alcohol.
T a b l e 2 1 . 7 Performance of energy cane
Source: SBI, Coimbatore.
21.5.1 Efficiency of phytomass production in energy cane
It is a common truism that sugarcane is one of the most efficient plants for converting solar energy to stored energy (sucrose). Only the giant sequoia tree (Sequoia gigantea) surpasses sugarcane in phytomass production (Humbert, 1975). On an average, sugarcane produces 35-90 t ha -1 dry matter. This author has harvested 60 t ha-1 of dry biomass for cane grown in red, sandy loam soils. However, the energy cane produces a much higher amount of biomass than some grasses and trees like Eucalyptus (Table 21.8).
348
21 By-products of the sugar industry: recent trends
Table 2 1 . 8 Biomass yield of some grasses and trees
The extended growing season and higher rate of leaf area production linked to
specialized carbon synthesis (C4 of malic and aspartic acids) are responsible for
the high phytomass production in sugarcane as compared with other C3 plants.
However, differences in dry matter production, including the fibre of Saccharum
spp., are mainly due to differences in leaf area rather than due to differences in
photosynthetic rates (Alexander, 1973).
A breakthrough in biomass production seems to be in the offing (Anon. 1990),
if large quantities of the chloroplast enzyme, ribulose bisphosphate carboxylase
oxygenase (Rubisco) are produced. This is a key enzyme in CO2 fixation, ac
counts for 5 0 % of the p ro te in in the green leaf and is bu rned dur ing
photorespiration.
21.5.2 Food vs fuel farming
Globally, the potential land area available for cultivation is 3419 million ha and
no additional land can be made available for biomass production. It was feared
that energy farming would possibly compete with food crops for scarce resources
like land, water and chemical fertilizers. But this theory has been discounted since
biomass is 'man's friend' and a companion for all seasons. In fact, Tudge (1988)
349
Sugarcane in agriculture and industry
warns that biomass production is a sine qua non, not only for the survival of mankind but also for the survival of 'fellow species'. To obviate the spectre of a serious competition between food and fuel crops, Lipinsky (1978) suggested the integration of fuel production with the food, material and residue systems. Agronomic packages such as close spacing, coppicing, ratooning and multiple cropping are available to increase yields and reduce the unit biomass cost.
21.5.3 Ethanol from fermentable solids
By far the most ambitious programme for the production of alcohol from sugarcane and other energy crops was launched in Brazil under the National Alcohol Programme (PNA or proAlcol). During 1997-98, Brazil produced over 12.5 billion litres of alcohol, and up to 22-25% of this alcohol can be blended with petrol. A flow diagram showing the production of fuel alcohol from either primary juice or High Test Molasses (HTM) or Black Strap Molasses (BSM) is presented in Fig. 21.4.
Lipinsky (1978) even suggested controlled production of crystalline sugar and if the sugar prices are low, substantial quantities of ethanol may be produced from the primary juice. It can be seen that H T M is distincdy superior to BSM and about 18 litres HTM are equal to 22.5 litres BSM. In fact, H T M is as good as the syrup or meladura (term used in Latin America). (Syrup or meladura is the liquid at the end of the last vacuum-boiling cells or bodies and has 65% solids and 35% water.)
Yeast cells or their extracts are used to ferment molasses and alcohol is distilled. Recent research suggests that the yeasts Saccharomyces cerevisiae or S. uvarum can be replaced by the bacterium Zymomonas mobilis for higher ethanol production from molasses. The Biostil process seems to have the edge over other processes in ethanol production (Paturau, 1986). This process was developed by Alfa-Laval of Sweden. Here, the fermentation environment is not limited by the final ethanol concentration but by the total osmotic pressure due to the accumulation of soluble non-fermentables in the fermenter. With this process only 60% of the conventional amount of processing water is required. Other advantages include minimal energy consumption and maintenance of a high and stable yeast population (Paturau, 1986).
The stillage or slops from the distillery poses environmental problems. The
volume of stillage produced is about 13 times that of the alcohol produced and its
BOD (Biological Oxygen Demand) exceeds 25,000 ppm. Stillage disposal is
350
21 By-products of the sugar industry: recent trends
achieved through fertilization, irrigation and biogas production. Vinasse, a distillery waste from fermentation is used as a soil amendment and fertilizer. Its application to latosols has improved soil aggregation and increased the pH, organic carbon, base saturation and CEC. It is a good source of K fertilizer and also supplies other minor elements like Zn, Fe, Mn and Cu.
Fig. 2 1 . 4 Flow diagram to show the production of ethanol from energy cane
21.5.4 Ethanol from celiulosic materials
Ethanol production from fermentable solids has overshadowed the potential of its production from celiulosic biomass. Hydrolysis of cellulose can be accomplished
351
Sugarcane in agriculture and industry
with acids or the enzyme cellulase; the latter is cheaper and more cost effective. Lynd et al. (1991) have described the steps involved in ethanol production from cellulosic biomass through an enzymatic process. The energy output-input ratio of this system is 5 and the value is likely to increase when more efficient fermentative microbes have been identified.
In the fermentation process the quality of the biomass is i m p o r t a n t ; hemiceliuloses or lignins are not easily degraded. It is seen that sugarcane bagasse has a higher cellulose content than corn and Pruett (1981) has shown that mutant strains of Clostridium sp. are efficient converters of cellulose or hemicellulose to ethanol. More recendy, Landisch and Svarezkopf (1991) stressed that the ability to ferment pentoses (xylose) is a key challenge and microbes like Candida tropicalis and Pichia stipitis are efficient in this area.
Lynd et al. (1991) have cautioned that the high costs involved in producing ethanol from cellulose are a major impediment to utilizing this technique. The production of ethanol from cellulosic biomass is a developing technology, and significant improvements are possible in the areas of pretreatment, enzyme activity, production, recycling and developing energy-rich crops.
21.5.5 Fuel alcohols
Biofuels like methanol and ethanol are the fuels of the future. Methanol has more problems of pollution than ethanol. The latter has a higher calorific value than the former. If the sugar prices are low, ethyl alcohol can be directly manufactured from the primary juice or High Test Molasses (HTM) or Black Strap Molasses. (BTM) Brazil holds the world record of producing over 12.5 billion litres of alcohol (ethanol) per year which is blended up to 22-25% with petrol. This is known as gasohol. For the record more than 90% of alcohol can be used as motor fuel. Biostil process or one step continuation process is employed. However the continuous fermentation or cascade fermentation process is favoured as it gives good ethanol yield and yeast recovery (Zerpelon and Andrietti, 1995). But ethanol is costly due to additional processes. On the other hand, industrial alcohol is cheaper and can be blended with petrol in equal proportion (50 : 50). Industrial alcohol has 5% water, hence such petrol is called 'Aqua petrohol'.
The new blend has an octane number of 98 with high efficiency. The techno-economic feasibility of blending ethanol with petrol is succincdy described by Goel
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21 By-products of the sugar industry: recent trends
and Sharma (1996). Anhydrous ethanol blends up to 10% with petrol are optimum giving greater power output with 60% lowered CO emission. Ethanol is an useful oxygenate and blending acts as an octane booster. In times of surplus cane, a provision should be made to produce ethanol direcdy from cane juice. The alcohol recovery is expected to be 70-75 litres per ton of cane, depending on the cane quality. These biofuels give lean burn with less emission of gases like CO, CO2 and NOx. Hence they are less polluting and ecofriendly. Despite the advantages of biofuels, economic parameters suggest that these would be economical only if the crude oil price is US$ 60 per barrel. Nonetheless, the importance of fuel alcohol is recognised as it reduces our import bills and the Government of India would permit a 10% blend in petrol. By the turn of the century, the alcohol requirement of India is projected at 4717 million litres per annum, which is used in organic chemicals, pesticides, pharmaceuticals and for industrial and potable purposes.
21.5.6 Molasses
Apart from bagasse, molasses is an important by-product of the sugar industry. It is another liquor left over after crystallization of sucrose from which further quantities of sucrose cannot be recovered economically (Singh and Solomon, 1995). The yield of molasses is 2.2 to 3.7% per ton of cane crushed. During 1997, there were 459 sugar factories with a total production of about 7.0 million tons of molasses per annum. Nearly 90% goes to produce industrial and potable alcohol and about 7—8% is utilised for animal feed. Valuable products such as pyridines and picolines are used for synthesis of drugs and pharmaceuticals. Certain microbes use molasses to produce oils and fats. Strains of eukaryotic microorganisms feed on molasses to produce oils of C—16 and C—18 fatty acid chains. A conversion of carbon into 20% lipid is possible. Microbial lipids include phospholipids, sterols, fatty acids and triglycerides.
There has been a steep rise in the price of molasses. After decontrol it is sold at Rs. 1000 per ton.
During 1997-98, there were 295 distillery units in India, producing over 1200 million litres of ethanol per annum. The traditional method of fermentation is through yeast cells (Saccharomyces sp.). New strains of Saccharomyces would gready improve the yield of ethanol. However, in recent times the Vacuferm and 'flash ferm' processes replace yeasts with the bacterium Zymomonas mobilis. The biostil technology (continuous process) developed by Alfa-Laval of Sweden has tremendously increased the
353
Sugarcane in agriculture and industry
ethanol yield from cane molasses. The strain referenced 493 has better fermentative
activity than the commercial bakers yeast. Supplementation to the media of sterols
extracted from press mud at the laboratory stage has enhanced ethanol production.
The important co-products via ethanol are shown below.
Organic acids and other value added products from mo/asses
From ethanol, various organic acids are produced through fermentation. These are: lactic acid, acetic acid, tartaric acid, maleic acid, and fumaric acid. Lactic acid is widely used in jams, jellies, dairy products, soft drinks, pickles and canned vegetables and fish products. It is possible to produce technical and plastic grade lactic acid from cane molasses. Diluted molasses are fermented by the bacteria Lactobacillus dudbruckii or L. bulgaricus. The fermentation is complete in 2—3 days and neutralised by calcium. Lactic acid is recovered from calcium lactate. Acetic acid and acetone are other alcohol based chemicals. Citric acid is manufactured from, molasses by fermentation with Aspergillus niger. This organic acid is very versatile and is used in pharmaceuticals, textiles, food and leather industries. Other products of value are glycerol, acetone, butanol and dextran. Lysine is an essential amino acid for nutrition, particularly of animals. T h e mutan t strains of. Corynobacterium (C glutamicus-ATCC-13022) ferment the molasses to produce L-Lysme. Acomtic acid and itaconic acids are extensively used in the preparation of plasticzers, wetting agents and also used as flavouring agents. Itaconic acid is produced from molasses by using strains of Aspergillus terreus at pH 1.8. This acid is used in resins, plasticizers and lubricating oils, and additives.
354
21 By-products of the sugar industry: recent trends
The biocide from cane molasses inhibits the activity of Leuconostoc bacteria. With this sugar factories can prevent post-harvest losses. A new explosive known as Nitromiel has been developed from cane molasses and ammonium nitrate. An important drug, Ephedrine hydrochloride which is extensively used in cough syrup is made from molasses . India produces about 30 tons of ephedrine per annum.
Monosodium glutamate (MSG) and baker's yeast are the other value-added products obtained from cane molasses. MSG is used as a flavouring material in meat preparations. It is produced in large quantities in Japan and is known as Ajinomoto. Molasses are fermented using Micrococcus glutamicus and the resultant glutamic acid is retrieved as sodium salt to obtain MSG. India can manufacture MSG on a large scale through 'buy-back' arrangements.
Molasses is the main raw material for the production of different types of yeasts, including baker's yeast by fermentation. The yeast generally consists of selected cultures of Saccharomyces cerevisiae. The baker's yeast is generally used in the manufacture of bread but it is also used to ferment molasses into ethanol. Torula yeast known as Single Cell Protein (SCP) is produced by a special fermentation process. SCP is gainfully used in milch cattle to improve milk yield. SCP is valued due to its high multiplication rate, rich protein content (30—80% dry weight basis) and simple, energy efficient system. This has high export potential.
It is to be noted that mutant strains of Trichoderma reesei can produce cellulase from bagasse and SCP from molasses.
Animal feeds from molasses
Molasses is the cheapest source of energy for animals and its feeding value was recognised as early as the 19th century. The composition of molasses is given in Table 21.9.
Due to sulphitation process, the sulphur content is also high in molasses produced in India. The total digestibility is around 60%. It is used to improve palatability or as binding material for pelletized diets or as a medium for adding certain nutrients.
It is a poor source of protein and anything more than 10% with roughages may lead to 'molasses toxicity' (animals show excessive salivation). Edible molasses have been developed by de-ionization of sugarcane juice with ion exchange resins. The protein molasses are a blend of carbohydrates and proteins with the final product containing 15-16% protein and 30—40% dry matter.
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Sugarcane in agriculture and industry
T a b l e 2 1 . 9 Composition of molasses
In Cuba, a technology has been developed to mix molasses with liquid Torula yeast. Yeast is an important ingredient of many commercial products and Saccharomyces cerevisiae is the standard yeast for the manufacture of ethanol, bread and bakery products. But the ideal yeast for food and feed from molasses is Torulopsis utilis due to its high content of proteins and Vitamin B complex group. Another feed known as 'yeast sludge' is obtained as an organic residue at the end of the fermentation process. After condensation to 65-75% dry matter, it is called condensed molasses solubles (Yeast sludge). This product is a rich source of microbial protein and is a useful ingredient of animal feeds. In Australia, molasses are fed to beef catde as 'cattle licks', stock blocks (solidified molasses and salt blocks), home brew licks (mixture of grains, molasses, urea, meat or bone meal) and fortified molasses (mixture of molasses and urea). The National Diary Development Board (NDDB), Gujarat, India has developed urea-molasses licks (animal chocolates) for animals. A similar product known as 'uromol' has been developed by the Pun
356
Press mud is increasingly being used as a fertilizer. It is a rich source of C, P and Ca. In more recent times it is enriched to ensure better fertilizer use efficiency. In Cuba press mud, bagasse and trash are recycled by the vermicomposting process and the enriched PM is called 'Begefert'. Some sugar factories in India produce enriched PM by treating it with spent wash and stirring the mixture well. After 4-6 weeks N-fixing bacteria like Azospirillum is added to obtain a balanced fertilizer known as 'Bioearth' or 'Green plus'. We have made 'Phosphogreen' by mixing
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21 By-products of the sugar industry: recent trends
jab Agricultural University, Ludhiana by heating urea and molasses in the ratio 1 : 9 at 110 °C.
21.5.7 Press mud or filter cake
The production of press mud in India ranges from 3.3 to 3.6 million tons annually as against the global production of 17 million tons. While manufacturing cane sugar, the impurities in the juice settle down and are removed as filter mud or Press Mud (PM). PM is a soft, spongy, amorphous dark-brown material containing sugars, fibre, wax, etc. besides inorganic constituents like N, P, K, Ca, Mg, Fe, and Mn. In a sulphitation process a good amount of sulphur is found in PM. The typical composition of PM is given in Table 21.10 (Singh and Solomon, 1995).
Table 2 1 . 1 0 Typical composition of Press Mud (PM)
Sugarcane in agriculture and industry
Rock phosphate/North Carolina phosphate/Tunisian phosphate (Gafsa) at the rate of 1/20 or l/25th of press mud (w/w). Cowdung slurry was sprinkled and thoroughly mixed with a rotovator. This was allowed to decompose for 4 - 6 weeks. There is an exothermic reaction with the evolution of heat and CO 2 . When press mud is stabilised in 4-6 weeks, diazotrophs such as AzotobacterlAzosprillum were added at the rate of 1-2 kg per ton of the product. To hasten decomposition Trichoderma viridae or Pleurotus sp. are added. Cowdung slurry is sprinkled which acts as a starter material. Usually one kg of these microbes, 5 kg urea and 50 kg cowdung are added The final product is a darkish brown powdery material and can be used safely for plantation/horticultural crops or in floriculture or in nurseries. The phosphogreen contains 9-10% P 2 O 5 besides other major, secondary and micronutrients. This is known to circumvent the imbalance in NPK fertilization of field crops by providing adequate P and K to plants.
Waxes are pliable material and are the esters of higher fatty acids. In sugarcane waxes are found in leaves but mostly on the rind portion of stems. Waxes are composed of lipids which are 0.18% of cane. There are distinct wax bands or rings on sugarcane stems. They form a waterproof protective coating. Varieties with high wax content are Co 290, B 37161, Co 997, etc. Waxes on stems resist biotic and abiotic stresses. It was seen that Co 997 with a high wax coating can resist drought better than POJ 2978 (low wax). Wax coating is also associated with a natural resistance to many insect pests and diseases.
358
Source: Shrivastava, 1995.
21 By-products of the sugar industry: recent trends
Waxes are solvent extracted from press mud (Shrivastava, 1995). Maximum cane wax is extracted with toluene at a temperature of 75 °C, solvent ratio 1 : 4, in 4 hours time and the PM particle size was 900 microns. The yield of crude wax ranges from 10.5 to 14.5%. The crude wax is further refined through solvent extraction to obtain refined wax. A flow diagram of cane wax extraction is shown in the previous page.
Waxes are used in pharmaceuticals, shoe polishes, varnishes, printing ink, carbon paper, etc.
21.5.8 Distillery effluents
After the recovery of ethyl alcohol from molasses, the residue contains slops/stil
lage/vinasse and yeast sludge. Carbon dioxide is also produced during fermenta
tion. Yeast sludge is a rich source of vitamins. It is mixed with animal feed to
improve its nutritional quality. Annually India produces 1000 million litres of
alcohol and 15000 million litres of spent wash, which cause serious environmen
tal problems. The distillery effluents are known as stillage (Vinhoto), Vinasse,
slops, still residue, spent wash, etc. Spent wash is acidic (pH 4-5) containing 9 0 -
9 3 % water. This is rich in Ca, K, Mg, P, S, N, Fe, Mn, Cu, and Zn. The disposal
options include dehydration, extraction, fermentation, and incineration. After
lagooning in the ponds, it can be used as ferti-irrigation. Sprinkler irrigation with
Vinasse is more efficient than soil application. Spent wash can also serve as a
liquid fertilizer when properly blended with NPK. Many experiments on sugar
cane have demonstrated a 30—40% increase in sugarcane yield (both 1st and 2nd
ratoons) following its application at the rate of 15,000 to 20,000 gallons/ha. Vasant
Dada Sugar Institute (VSI), Pune has developed a method to prepare an organic
manure. The slop is limed to pH 10.5—12.5 and concentrated to 70—80 brix. The
concentrate is mixed with dried filtered mud or begacillo and sold to farmers as
manure. The other alternative is that the limed spent wash is mixed with press
mud and phosphoric acid and sold as Vinasse cake.
The most important method of composting is 'bioearth' preparation. Herein,
press mud is arranged in wind rows, 2 m high and 1 5 m wide at the base. Boiler
ash and bagasse are also mixed. Spraying of effluent is done to maintain optimum
moisture levels with frequent stirring with rotovators. Microbial starter 'Fabearth
micro 110' is employed to enrich the compost. Godavari Sugar Mills, Sameerwadi
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Sugarcane in agriculture and industry
produces an organic manure 'Bhumi Labh' by treating press mud with spent wash
and bioagents. 'Bhumi Labh' is useful for many field crops, plantations, vegetable
and horticultural crops. Using 'Bhumi Labh' results in an enormous saving of
chemical fertilizers.
Application of Vinasse per se has reclaimed saline/sodic soils. Its application
improves pH and CEC with a consequent increase in cane height, girth and yield.
The application rate ranges from 30-70 m3/ha depending on the soil type. This
can save chemical fertilizer up to 30% in 3-4 years. These findings need confir
mation.
Vinasse can also be used for production of biogas (methane) and desalting to
obtain potassic fertilizer. Due to its high silicon content, Vinasse can also be used
as a building material.
2 1 . 6
POWER CANE SYSTEM
As we enter the new millennium, sugarcane would be commercially metamorphosed to power cane as cogeneration of power assumes a pre-eminent position in the national economy. Almost all the states in India suffer serious power shortages.
Sugar factories are self-sufficient in fuel and power. But with efficient utilization of surplus bagasse, power can be generated. The concept of cogeneration was started in Hawaii and most factories in developed countries are providing surplus power to the national grid or run ancillary industries. The cogeneration of power is viable due to the improvements in technology. These include use of higher efficiency boilers, use of higher steam pressures and temperatures, heat conservation in factory operations, installation of bagasse dryers and energy saving devices and equipment. It is logical to conclude that a mill of 2500 T C D (Tons Cane per Day) can generate excess power to the extent of 5-6 MW which can be fed to national/state grid. This power can gainfully be employed to run other subsidiary industries. India has more than 500 sugar factories of varying capacities ( 8 0 0 -10,000 TCD) that can generate surplus power to the extent of 3800 MW. The assumption is that average mills can generate additional power in the range of 6 0 -80 KWH/ton of cane crushed. Thus a 2500 T C D plant can earn additional revenues of over 3 crores (power tariff Rs. 0.80 to Rs. 1.25 per unit) in a season.
360
21 By-products of the sugar industry: recent trends
Further, trash can be used as off-seasonal fuel. It is baled as round big bales or
small square bales. The Net Calorific Value (NCV) is around 12,600 J kg -1 which
is much higher than that of bagasse. The latter has more moisture content, and
hence less NCV. Production costs per heat energy unit are comparable to conven
tional fuel sources (Jakeway, 1995).
Box III
Bio-feeds from sugar industry at a glance
Sugarcane agro-industry by-products have played a decisive role in animal production in the tropics. At present this industry provides, in addition to yeasts, six different products intended for animal feed. They include: molasses-urea mix, molasses-urea-pith mix, pre-digested pith, dehydrated fdter cake, high protein molasses and crop residues (leaves and tops).
Several heads of cattle were fed with only dry-cleaning station residues. This line of production has a higher potential and with simple technological solutions could also improve the efficiency in the use of cane top residues.
Source: Almazan, 1994.
361
araauaaaaa
Pollution problems and control measures
Effluents from sugar and other allied industries with lot of organic material are discharged into rivers, streams, canals, and lakes. These effluents are allowed to settle in open fields and ponds. Fermentation sets in causing the emission of foul odour. The effluents can find their way into seepage water and pollute the ground water. Besides liquid wastes, there are solid wastes, i.e. bagasse, press mud and fly ash. The gaseous wastes consist of CO and SO 2 . The bagacillo and fly ash floating particles cause air pollution. With well-designed fly ash separators, fly ash can be tripped as a land fill. It is to be noted that a 2500 T C D plant uses about 0.75 tons of sulphur that escapes as SO2 in the range of 6—8 kg/day in the sulphitation process. The effluents can be treated with biological agents to produce biogas, biofertilisers, antibiotics, enzymes and other value-added products. Thus, the bioprocessing of distillery and other wastes of the sugar industry leads to wealth from wastes (Mala et a!., 1998).
The major wastes come from mill, boiler and centrifugal houses, l ime house, etc. besides lab and floor washings. Oil, grease and surplus molasses are discharged with a consequent high pollution load. The main effluent volume is 4500 to 5000 1 ha - 1 with acidic reaction. The Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) are 2000-3000 and 800-1500 respectively. Some precautionary measures to reduce the pollution loads include:
(a) Avoidance of leakage of juice, syrups, sugars and molasses from pipes, valves, etc.
(b) Avoidance of oil and grease leakage on the floor or into drains or their mix up with effluents.
It is preferable to provide grease taps to arrest leakage of grease/oil into the
mill house drains. The State and Central pollution boards have set the stand
ard B O D discharge limits. The limits are 30 mg 1 -1 and 100 mg 1 -1, if the
effluents are discharged into rivers/streams and land masses respectively.
2 2 . 1
EFFLUENT TREATMENT METHODS FOR THE SUGAR INDUSTRY
The effluent treatment methods are categorised into three types, namely, physi
cal, chemical, and biological methods (Shukla, 1995).
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22 Pollution problems and control measures
22.1.1 Physical treatment methods
These treatment methods include use of coarse and fine screens made of boulders, sand, etc. sedimentation techniques, and oil and grease removal. Other methods employed are dilution with water to reduce pollution loads, sun drying, and incineration. This constitutes essentially a primary treatment to partly reduce the BOD.
22.1.2 Chemical treatment methods
A change in effluent quality is brought about by treatment with chemicals
such as lime, alum, chlorine, and potassium permanganate/dichromate. How
ever, these are expensive and not economical in a sugar factory.
22.1.3 Biological treatment methods
This is a natural process of purification and is, hence, economical. These are
grouped into three categories: (a) anaerobic system (b) anaerobic system fol
lowed by aerobic system (semi-aerobic) and (c) totally aerobic system.
For high pollution loads as in the distillery, paper and pulp industries, the
anaerobic system is more efficient. But for low pollution loads as in sugar
factories aerobic treatment is suited where B O D loads can be brought down
to 30 mg l-1 or even less.
(a) Anaerobic system: In this system, lagoons or deep ponds (2—6 m) are
made where organic material of the effluent is partly decomposed to
methane at the bottom layers. At the surface layers bacterial oxidation
takes place as the wastes enter the lagoons. The suspended organic mat
ter, bioflocculants, and colloidal matter settle down at the pond bottom.
The settled sludge undergoes anaerobic fermentation with the liberation
of methane. At the top layers aerobic bacteria promote oxidation of or
ganic wastes. Thus the symbiosis of anaerobic and aerobic bacteria is
responsible for B O D reduction. The 'kaccha' lagoons may lead to foul
odour and the seepage of effluents pollutes the groundwater. Hence 'pukka'
lagoons which are made of bricks and cement are suggested. Removal of
B O D is to the extent of 70% in about 4 weeks. The treated effluent can
363
Sugarcane in agriculture and industry
be used for irrigation with 1 : 2 dilution. The bacteria associated with
anaerobic decomposition are: Clostridium, Megaspore, Methanococcus,
Methanomonas, Sarcina and Streptococcus sp., etc.
In the first stage of anaerobic effluent treatment, large molecules are hydrolysed by extracellular bacterial enzymes to produce sugars, fatty acids and amino acids. In the second stage, sugars are converted to organic acids such as acetic acid, butyric acid, formic acid, etc. through the acid forming bacteria. In the third stage, methanogenesis takes place by methane forming bacteria to produce methane, CO 2 , H 2S, N H 3 , etc. Ultimately aerobic conditions need to be created for complete stabilisation and removal of bad odour. Water hyacinth is also grown in the ponds but large biomass disposal is a serious problem. Anaerobic contact filters followed by aerated lagoons are a better option.
(b) Anaerobic cum aerobic process: The main effluent is passed through screens, and oil and grease removal tanks. The effluent then enters an anaerobic tank through an equalization tank. The effluent from the anaerobic tank is passed through a battery of aerobic pits or shallow ponds (1 m deep). The latter are fitted with agitators. The oxidation process is catalysed by algae, chlorella, etc. Considerable reduction in BOD is achieved with the evolution of C O 2 , water, and heat. A sketch of the Effluent Treatment Plant (ETP) is shown in Fig. 22.1. The cost of ETP is likely to be high due to 'pukka' tank and aerators. It has been observed that anaerobic filters followed by aerated lagoons are a better option.
(c) In the activated sludge process (Fig. 22.2), the effluent after the primary
treatment is carried through an equalization tank where pH and nutri
ents are adjusted and mixed with 2 - 5 % sewage (Shukla, 1995). It is
then taken to an aeration tank where aerobic decomposition takes place
with the help of aerobic bacteria. Sludge or biomass is recycled from the
aeration tank to the equalization tank. The excess sludge is led to drying
beds. Flocculation in a gelatinous mass is an important property of acti
vated sludge and achieves 8 5 - 9 5 % B O D reduction. Colloidal action
also results in flocculation. Flocculation is chiefly carried out by mi
crobes such as Zoogles remigera and some protozoa.
364
22 Pollution problems and control measures
Aerobic oxidation tank
365
Fig. 2 2 . 1 Effluent Treatment Plant (ETP) of sugar factory using an anaero
bic cum aerobic process (Source: Shukla, 1995)
A combination of activated sludge system and biofilter can work better
and give the needed B O D limits of the waste. Biofilters (Fig. 22.3) are
'pukka' cylindrical tanks 10-15 m in diameter and 2 - 3 m in height.
The bottom of the tank is perforated for trickling of the liquid and is
well ventilated through side walls.
Sugarcane in agriculture and industry
Fig. 2 2 . 2 Activated sludge process to treat effluent
366
Fig. 2 2 . 3 Biofiltration process
22 Pollution problems and control measures
The tank is seeded with bacteria, nutrients in the form of urea, phosphate, and sewage. The bacterial film is formed over the tank surface and greatly aids in the decomposition of organic material. It is to be noted that bacterial sludge decomposes all types of wastes under aerobic conditions. Sludge is a heterogenous mass (biomass) and B O D is reduced with the release of CO 2 , water and biomass. The microbes implicated in the reaction are: Zooglea remigera, Nocardia, Actinospora, Bacillus, pseudomonas, Sarcina, Escherichia, Flavobacterium protozoa, etc. Hydrogenases and dehydrogenases are the active enzyme systems to decompose organic matter.
22.1.4 Air pollution
The air pollution from the sugar industry consists of SO2 , CO2 and Suspended Par t icula te Mat ter (SPM) in the form of fly ash. E q u i p m e n t such as multicyclones, water scrubbers, fly ash arresters, bag filters and electrostatic precipitators are employed to check air pollution. Different pollution control boards in India have recommended SPM in the range of 250—800 mg/N m3
for different types of bagasse fired boilers.
22 .2
EFFLUENT TREATMENT FOR DISTILLERY UNITS
The important by-products of the distillery units are: CO 2 , yeast sludge, and
spent wash. Yeast sludge is a rich source of vitamins and can be mixed with
fodder and fed to cattle. The distillery wash is named as slops, dunder, efflu
ent, stillage, and vinasse. The volume of spent wash is 12—15 times that of
alcohol produced. A normal plant of 30,000 litres per day (LPD) capacity
generates 4,50,000 litres of spent wash per day.
The spent wash is highly acidic in nature and contains many organic and
inorganic substances. The average composition of spent wash is given in Table 22.1.
Because of its high BOD and C O D , spent wash when allowed to decom
pose in open ponds gives bad odour. It is more hazardous when discharged
into nalas, rivers, lakes, streams, etc. The disposal of spent wash is a serious
environmental problem.
367
Sugarcane in agriculture and industry
Table 22.1 Average composition of spent wash (g 1-1)
Source: Gehlawat, 1995.
Many physical, chemical and biological methods are suggested to treat the spent wash. Biological methods are more suited due to their low handling and maintenance costs. It involves a general process, an anaerobic process and an aerobic process.
22.2.1 General process
The effluent is diluted several times and used as irrigation water, specially in
the lighter soils. The waste can also be concentrated after neutralization with
lime in multiple effect evaporators and then dried in rotary drums to convert
it into cattle and poultry feed. Spent wash contains 0 .6-1.5% K. Hence it can
be neutralised and concentrated to form a cake. This cake can be used in boil
ers and the ash is a good potassic fertilizer (37% K2O).
22.2.2 Anaerobic digestion and methane production
The anaerobic process comprises three stages. In the first stage degradation of
organic matter to organic acid takes place by the action of saprophytic bacte
368
Spent wash has the highest BOD and COD values as compared to other
agro-based industries (Table 22.2).
Table 2 2 . 2 Values of BOD and COD of some agro-based industries
•-*>wrS"--">
22 Pollution problems and control measures
ria. The second stage involves acetogenesis with the formation of acetic acid and dehydrogenation. At this stage, acid forming bacteria participate. The third stage is methanogenesis, mediated by methane forming bacteria, with formation of methane (Fig. 22.4).
Fig. 2 2 . 4 Anaerobic digestion and methane production
The general reaction is:
In fact methane producing bacteria convert organic acids to methane. Four
genera are: Methano bacterium, Methano bacillus, Methano coccus and Methano
sarcina.
T h e anaerobic digestion is simple with a closed reactor (digester) and a
provision for gas collection. The retention time in the digester is 30—60 days.
B O D reduction is of the order 8 5 - 9 0 % , while C O D reduction is 6 5 - 7 0 % .
Methane content of biogas ranges between 6 0 - 7 0 % .
369
Sugarcane in agriculture and industry
At the National Sugar Institute (NSI), Kanpur, an ammonifying bacterial process has been developed for the first stage treatment of spent wash. Reduction in BOD is 90 -93%. In this process, an ammonifying bacterial culture is developed in the laboratory and then at distillery sites in drums. The full plant consists of a mixing tank, 3 settling tanks, 4 culture tanks, and 5 treatment tanks. The retention time is only 4—5 days.
In a normal distillery plant, biogas production is ~2800 m3 /d assuming a C O D reduction of 70%.
The Vasant Dada Sugar Institute (VSI), Pune, has developed a modified incineration method of effluent disposal known as DIEG—VSI process. It involves (i) concentration of spent wash to 50 -60% solids (ii) drying the concentrated wash in a solid form fit for burning (iii) burning of dried solids in fluidised bed combustion boiler (iv) utilisation of steam for DIEG process and running the distillery unit (Gunjal and Hapase, 1995).
Yet another method of effluent treatment is anaerobic lagooning, which is cheap and economical. But methane recovery is not possible. This is also a biological method where waste material is treated in lagoons or deep ponds, 2—6 m deep. After the lagoons are formed with earth material, they are seeded with cowdung and then loaded with spent wash. If needed, they are limed. Sometimes multiple lagoons ranging from 1 to 4 are used for waste treatment. After the waste treatment, the water can be used for irrigation purposes.
22.2.3 Aerobic process
The distillery effluents serve as raw material for the cultivation of torula yeast,
which can be used as cattle feed. The yeast is developed under vigorous aerat
ing conditions and BOD reduction is by 50%.
In the activated sludge process, biological growth takes place under aerobic
conditions. The wastes are continually fed, so that flocculant suspensions ag
gregate and settle. The process comprises sedimentation, aeration, and sec
ondary sedimentation. The mixed microbial population includes algae and
bacteria such as Zooglea, Pseudomonas, Nocardia, Actinophora, Sarcina,
Achromobacter, Flavobacterium, etc. This process is more suited to effluents of
low pollution loads (sugar factories) and second stage treatment of distillery
spent wash.
370
22 Pollution problems and control measures
In the aerated lagoons, algal and bacterial cultures are grown to treat the spent wash and BOD reduction is to the extent of 7 0 - 8 0 % .
2 2 . 3
BIOCOMPOSTING
There are aerobic and anaerobic processes of biocomposting of the wastes. The
biofertilisers are made by using press mud, spent wash and other micro cul
tures. These biofertilisers improve physical and chemical properties of soil be
sides supplying major and minor nutrients to plants.
T h e bioprocessing of distillery wastes leads to 'wealth' from 'waste'
(Mala et al., 1998). Biocompost has been produced by using press mud, efflu
ents, bioinoculum, and earthworms.
The bioinoculum consists of Trichoderma reesei, Aspergillus niger, A. flavus
and Bacillus sp. The treated water can be used for irrigation and serves as
'liquid manure ' .
Bioearth composting is an aerobic process. Press mud is arranged in windrows,
2 m high and 4 m wide at the base. Boiler ash and bagasse may be mixed with
it. Windrows are allowed to dry to some predetermined moisture. Effluent
and a special microbial starter, Fabearth microllo are sprayed on the heaps. The
spraying is carried out at regular intervals. The aerotiller agitates and aerates
the mixture well. This also ensures uniform mixing of the microbial starter.
The composting period is 8—11 weeks.
In the first method of aerobic composting, press mud and spent wash are
mixed in the ratio of 1 : 2.5. The water content of the mix is 60—70%. Ini
tially cowdung is used as starter material. Compost is ready in 20 days. The
composition of this compost is:
P H 6 .5-7 .5
N % 0 .4 -0 .6
P 2 O 5 % 0 .7 -1 .3
K 2 O % 2 .3 -3 .0
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Cane farmers and sugar policy
The cane farmer, big or small, is a key person and cane development activity centres around him. He is the supplier of raw material to the mill and deserves all our respect and regard. Cane development involves specialised public relations where all efforts are made to improve yield, sugar recovery and the financial status of the grower and the economic viability of the factory.
Various extension methods are adapted to disseminate new technologies. The success of extension methods depends on (a) identification of a problem (b) demonstration of a suitable technology and (c) inducing the farmer to adopt the technology on a large scale. Blackburn (1984) sums up that cane development is development of the grower who plants and cultivates quality cane and provides it to the factory. Hence there is need for mutual understanding, respect and trust between the farmer and the manufacturer. For maximum sugar output the cane should be crushed within 24 hours and the binding material should not be more than 3%. In India land holdings are small, ranging from less than 0.4 ha to more than 4.0 ha and mechanization is not easy. Manual harvesting is done and care should be taken to harvest the cane at the ground level.
Technology transfer is both an art and science. There must be a direct link between the researcher, extension worker and the farmer so that there is proper and timely feedback. Arulraj (1995) observed that due to lack of transfer of technology, a large gap exists between the potential and the actual yields obtained in India. He has suggested Integrated Technology Transfer (ITT) which entails three components.
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23 Cane farmers and sugar policy
The following tasks of the Cane Department assume primacy.
(a) Systematic survey of the reserve area in respect of soil problems, drought, waterlogging, pests-disease menace, and other biotic and abiotic stresses. They should identify the thrust areas to augment quality cane production.
(b) Detailed varietal scheduling.
(c) Model farms not less than 0.4 ha are to be maintained in the grower's fields to demonstrate the latest technology.
(d) Intensive educational programmes in the villages through group discussions, exhibitions, slide and video shows, and distribution of leaflets.
(e) Constitution of Salaha Samitis for awareness among the farmers about recent technologies and their impact.
(f) Supply of critical inputs like seed, fertilizers, herbicides, etc. through arrangements with banks and other financing institutions.
The import of technology transfer was studied by Arulraj (op. cit.) who found that the adoption of knowledge like new varieties, optimum sett rate, geometry of planting, sett treatment, trash mulching, earthing, ratoon management, etc. was only 25—34% with registered growers as against 14.05% in nonregistered growers. Cane development staff should update themselves about technological developments; they must be permitted to attend seminars, symposia, workshops and visit important research stations.
2 3 . 1
SUGAR POLICY
In the early 1930s, the British Government felt that the sugar industry had to be
protected and developed in the country. To cushion the industry from imports, the
Sugar Industry (Protection) Act of 1932 was passed by the Indian legislature. This
industry was protected for 14 years up to March 1, 1946. Various laws were made
and after independence these were subsequently modified by the Bhargava Com
mission. These laws served the purpose at that point of time but needed to be re
vised thoroughly to modernise and introduce the latest technology. This will not
only increase sugar production but also make sugar available at a much cheaper rate.
In 1936-37 there were only 140 vacuum pan factories with 9 refineries. The
production of sugar was 1.13 million tons. The industry has shown remarkable
improvement in productivity, both in the field and the factory. As on 28-2-1998,
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Sugarcane in agriculture and industry
there were 460 mills—66 Government owned, 140 private sector and 254 cooperative sector. The crushing period improved from 101 days in 1950-51 to 128 days in 1996-97. The area under cane stands at around 4.0 million ha, which works out to 2.2% of the gross cropped area. The cane yield has risen from 46.32 t ha - 1
in 1966-67 to 71 t ha-1 in 1996-97. The sugar recovery in 1950-51 was 9 .91% and rose to 10.03% in 1995-96. The highest recovery was in Maharashtra (11.07% in the period 1991-95 ) followed by Karnataka (10.44%) during the same period. Maharashtra has also more modern mills.
Today, India is the largest producer of sugar but is not the most efficient one. On an average a 14 month crop yields 71 t ha -1 as against 250 t ha - 1 in Hawaii for a 24 month crop. The combined productivity level in the country is 1.0 t ha - 1
sugar per month. If the average sugar yield is taken for a 14 month period, it works out to 0.5 ha -1 mo - 1 . For comparison, sugar yields in different countries are shown in Table 23.1.
T a b l e 2 3 . 1 Sugar yield (t ha-1) in different countries
Source: STA1, 1998, 1999.
Modernisation of sugar factories is the prime need. There are 165 factories in
India which are more than 35 years old. The minimum economic capacity of a
mill is 2500 T C D with expandable capacity to 3500 T C D . Most modern mills
have continuous sulphitation and liming, and only a few old mills have the car-
bonation process. Efforts are being made to get refined sugar through raw melt
phosphotation and ion exchange routes. These results are awaited.
Efficiency norms are given by Bhargava formulae (Bhargava Commission, 1974)
and the total losses are plugged at 2.3 to 2.7%. The break-up of losses is as below:
(a) Sugar loss in Bagasse (mill loss) 0 .9 -1 .1%
(b) Sugar loss in press matter 0 .1%
(c) Sugar loss in molasses (process loss) 1.2-1.4%
(d) Unknown loss 0 .1%
Total 2.3 to 2.7% Sucrose extraction is much lower in India as compared to other countries
(Table 23-2).
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23 Cane farmers and sugar policy
Table 2 3 . 2 Sugar extraction percentage in different countries
Source: STAI, 1998, 1999. The above data is taken for the period from 1989-90 to 1993-94.
The future belongs to by-product utilization. The major by-products are all types of paper, and particle boards. Cogeneration of power is a major step in the diversification of sugar industry. In Hawaii, sugar factories supply 10% of the power to the national grid. Sugar factories in Mauritius meet 26.3% of the national power requirement and the country plans to supply 75% power from sugar factories.
23 .2
ENACTMENTS
The Essential Commodity Act 1955 (EC Act) defines sugar that includes Khan-dasari sugar/bura sugar or crushed sugar or any sugar in crystalline or powder form. Under the Essential Commodity Act 1955, the Central Government would enforce levy sugar. The concept of levy sugar came into being from the 1967—68 sugar season onwards. The Act introduced dual pricing mechanisms (partial control). The policy of partial control continued except for brief spells of decontrol from 25 May 1971 to 30 June 1972 and from 16 August lof sugar978 to 16 December 1979. The levy sugar price was fixed by the Central Government.
The Sugar Control Order 1966 provides power to the Government to regulate the production of sugar, restrict sales, etc. of sugar by producers, issue directions to producers or dealers, and regulate movement of sugar and the quality of sugar. The Sugar Control Order 1966 provides guidelines regarding the fixation of the Statutory Minimum Price (SMP) for sugarcane purchased by sugar mills during each sugar season.
Invariably the State advised price is more than the Central advised price by Rs 5-10 per q . Sugarcane payment has to be made within 14 days of the delivery at the factory gate and any delay would warrant payment of interest at 15% per annum. The Sugar Control Order enforces payment of additional cane price to growers, regulates the distribution and movement of sugarcane, licensing of power crushers, khandasari units, and issues directions to producers of Khandasari sugar. It has power to call for information, search and seizure of the types of sugar. It also fixes the reservation of area to the factory.
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Sugarcane in agriculture and industry
The Sugar Control Order 1966 as amended on 9 September 1983 provides for payment of sugarcane price at the rate of SMP notified by the Central Government or at the agreed prices between the miller and the cane grower.
The Bhargava formulae are meant to enable the farmer to get a remunerative price for cane supplied after 1 October 1974 by sharing of the profits arising out of excess realization with the producer sugar factory. It is no longer mandatory according to the Sugar Control Order 1966 that all sugar manufacturers should export sugar. Exports can voluntary. The Sugar Control Order empowers the Central Government to issue directions to sugar producers or recognized dealers from time to time regarding production, maintenance of stock, storage, sale, trade, grading, weighment, disposal, etc.
The Sugar Cess Act 1982 was enacted to provide for the imposition of cess on sugar for the development of the sugar industry and matters connected with it. This Act empowers the Central Government to levy the cess by way of excise duty which would help modernise and rehabilitate the sugar factories.
The Sugar Development Fund (SDF) was enacted under the Sugar Development Act. The object of the SDF act was to render financial assistance through loans for rehabilitation and modernisation of sugar factories. SDF is also meant to improve cane development such as early rich canes, heat treated sugarcane seed and other R & D activities.
2 3 . 3
HIGH POWERED COMMITTEE RECOMMENDATIONS
This committee was constituted on 14 March 1997. This was headed by Sri B. B. Mahajan and comprised technical experts, representatives of cane growers, Central and State Governments. The committee was required to go through all aspects, review the rules and regulations to modernise the sugar industry and augment the production of cane and sugar. Some important terms of reference were to study the working of the industry in other sugar producing countries, and induce efficiency through modernisation so that sugar is available to the general public at reasonable prices. A fair and remunerative price should also be ensured to cane growers. Some of the recommendations are given below:
(i) There must be complete decontrol of sugar phased over a period of two years beginning with a reduction in levy sugar to 20% followed by complete decontrol in the following season.
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23 Cane farmers and sugar policy
(ii) Even after complete decontrol of prices, control on releases should be operated by a committee comprising a senior official of the Department of Sugar along with a representative each from the association and cooperative federation,
(iii) Supply of sugar through the Public Distribution System (PDS) should be discontinued. In case the Government wishes to continue sugar under PDS, they may purchase sugar from the industry or trade at a fixed price,
(iv) There must be a Sugar Pricing Board (SPB). Pending decontrol levy sugar prices should be based on the actual cane price paid by the sugar factories in the zone as determined by the SPB. The SPB will comprise an economist of repute as the Chairman, and officers not below the rank of Joint Secretary from the Department of Sugar, Civil Supplies, and Ministry of Agriculture, Economic advisor in the Ministry of Finance, one representative each of the association, cooperative federation, and two representatives of the cane growers—one from the tropics, another from the subtropics.
(v) Statutory Minimum Price (SMP) needs to be continued even after decontrol which guarantees a minimum price to the grower. SMP is computed only with reference to cost of cultivation and returns from alternate crops without relating to the sugar price. Cane prices will be fixed separately for different zones. In future, SMP should be linked to sugar recovery and the sugar content of cane. A premium may be paid for varieties which have high sugar content,
(vi) Khandasari units may also be required to pay the same SMP during the
normal crushing season, (vii) The final cane price payable to sugarcane farmers should be linked to the
price of sugar. The final cane price may be fixed separately for different zones, but within a zone all mills should be required to pay the same price. The formulae for determination of cane price is: Cane price per ton = Average price of sugar per quintal in zone during
the year x grower percentage share x average recovery in the zone during year/All India Average sugar recovery during the year
(viii) The mills are required to pay statutorily a minimum of 80% of the advance price determined by SPB or SMP, whichever is higher within 15 days of cane supply to the mill by the growers. The remaining amount out of the
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Sugarcane in agriculture and industry
advance price shall be paid by the mill before the end of the sugar season.
The difference between the advance price and the final price shall be paid
by the mills within 15 days of the announcement of the final price.
(ix) The maximum binding material may be fixed to 3 kg q_1 (3%) of sugarcane.
(x) Demarcation of the cane area has to be done for each factory so that a
compact area is available to the mill for a normal working season at optimum
capacity. It is preferred to demarcate the reserve area on a permanent basis.
(xi) The radial distance from an existing mill for location of a new mill may
be kept at 25 km. (xii) A regular annual export quota of one million ton of sugar should be per
mitted. In the event of complete decontrol, normal releases may be allowed over and above the quantity exported by the mill,
(xiii) Cane has to be registered with the factory and the bonded cane receives the price as determined by SPB even beyond the normal crushing season,
(xiv) Buffer stocks should be built out of surplus domestic production in good
years and not out of imports, (xv) Khandasari units may be permitted at a distance of 25 km from the mill site,
(xvi) Mills may opt for cogeneration of power or manufacture of paper and particle board from bagasse. Use of alcohol for mixing with petrol needs to be permitted,
(xvii) R & D should emphasise on the improvement of cane varieties, management of pests, diseases, weeds and abiotic stresses like drought, water logging, salinity. Tissue culture may be used mainly for the production of foundation seed and 40 ha land is allocated to a factory of 2500 TCD. For release of new cultivars 11.5% sucrose may be the benchmark at maturity,
(xviii) The existing policy of licensing for new mills may continue but it is necessary to ensure that the new mill is not installed very close to the existing factory or factories.
(xix) In order to provide a level playing yield to domestic producers it has
recommended an import duty at 4 0 % of average difference between ex-
factory price of free sale and levy sugar during the past 5 years. This amounts
to Rs 150 q_1. In addition, Rs 85 q_1 is levied to cover excise duty and cess
on sugar and Rs. 50 q_1 to cover incidence of taxes on purchase of sugarcane
levied by the coastal states.
These recommendations are yet to be accepted by the Government.
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Economics of cane cultivation
Among the commercial field crops—sugarcane, cotton, potato and tobacco—
sugarcane is the most preferred for cultivation due to the following reasons. (i) Price is fixed well in advance. (ii) Market is assured.
(iii) In most areas, harvest and transport are done by the factories. (iv) Good profits are ensured.
In some years, cane supply far exceeds the demand due to excessive planting (more than the crushing capacity of the mill) and/or the mechanical failures of the mill. To realise the maximum profits, all inputs should be provided in time, mostly in the first 100 days. Sugarcane, being a grass has fewer problems of pests and diseases and tolerate many biotic and abiotic stress conditions. Above all, it responds to management.
It has some disadvantages. It is a long duration crop extending from 10 to 18 months, and is labour intensive. Due to paucity of labour and high wages, the cost of cultivation is increasing year by year with consequent reduced profits. The input costs like that of fertilizers are also on the increase. To achieve maximum profits and returns the following measures need to be taken, (i) Optimum utilization of inputs, (ii) Timely application of fertilizers, herbicides, etc.
(iii) Regular irrigation schedules to meet the crop demand but no over-irrigation, (iv) Procurement of healthy, preferably heat treated setts or seed pieces.
Several studies have shown there is a considerable yield gap between the potential and actual yields and this gap can be reduced.
The scientific economic analysis of plant and ratoon cane grown in tropics was done and is presented in Tables 24.1 and 24.2. The Variable Cost (VC) include fertilisers, seeds, etc. The fixed cost include land rent, interest on the capital, etc. Ten per cent of the Variable Cost (VC) is assumed as fixed cost.
The plant crop requires about 300 mandays per ha excluding the labour required for harvest and wrapping and propping operations. On the other hand, ratoon requires about 230 mandays per ha excluding the labour required for harvest and wrapping and propping. For harvesting contract labour is taken but herein calculations are shown based on casual men or women labourers. The operational wise break-up of the variable cost of cultivation for the plant crop is given in Table 24.3.
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Sugarcane in agriculture and industry
380
24 Economics of cane cultivation
381
Sugarcane in agriculture and industry
382
24 Economics of cane cultivation
383
Sugarcane in agriculture and industry
384
24 Economics of cane cultivation
Table 2 4 . 3 Operational wise break-up of cost of cultivation for plant crop
It is gleaned from Table 24.3 that the maximum expenditure is on harvest and transport (28.06%) followed by manures and manuring (24.87%) and seeds and sowing (22.75%). About 30—35 irrigations are given in tropical India, the expenditure comes to about 5% of the variable cost. The variable cost per ton is Rs 317. The benefit cost ratio (B : C) is around 2 : 1 .
The total cost is calculated as under: Total cost includes variable cost + fixed cost.
VC Rs 49,150 Fixed cost (a) 10% of the VC 4,915 (b) Rental 1,000 (c) 14% interest on VC 6,881
Total 61,946 B:Cra t io 1.58:1 It is seen that the total cost (variable cost + fixed cost) comes to Rs 61,946 per
ha with a benefit cost ratio of 1.58. To be economically viable, B : C ratio should
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Sugarcane in agriculture and industry
be at least 2.0 and above. To improve profits, there must be conscious efforts to
improve the yield to at least 175—200 t ha - 1 to justify such high expenditure on
cultivation. It is, therefore, surmised that the target yield is necessary and accord
ingly the cultivation costs have to be incurred.
Sundara (1998) has given the input-wise break-up of cultivation costs and it is
presented in Fig. 24.1. Nearly 50% of the cultivation cost goes to manual labour
followed by seeds and manures. To improve the profits, input cost has to be re
duced without sacrificing the yield and quality. It is postulated that a high input
cost is justified when the yield level is about 175-200 t ha -1. Mechanization is
also thought of as a measure to reduce the input costs. Agronomic and other
measures have to be adopted to improve the efficiency of fertilizers and irrigation
water. In tropical India very little is spent on pesticides but a need-based approach
is highly desirable.
Ratoons are more profitable than plant crop. To raise a ratoon crop only 230
mandays are required as against 300 mandays for plant crop. There is a saving in
seed. The variable cost (VC) is Rs 37,215 while the total cost (VC + fixed cost) is
Rs 47,146. Based on variable cost, B : C ratio is 2.57. The cost of producing one
ton of ratoon cane is Rs 266. The break-up of inputs in respect of various opera
tions in ratoon is given in Table 24.4. The maximum expenditure is on manures
and manuring followed by harvest and transport. The profitability of a ratoon
crop is possible by proper gap filling by polythene raised 6-week-old-seedlings.
Fertilizer use efficiency is improved by point placement of urea super granules,
press mud application and trash mulching.
Input-wise break-up of cultivation cost for ratoon cane is presented by Sundara
(1998) and is depicted in Fig. 24.2. As in the plant crop, maximum expenditure is
towards labour input (57%) followed by manures and fertilizers. Here again mecha
nization of stubble shaving, intercultivation and shoulder breaking increase the
profitability of ratoon cane. Sundara (1998) has shown that for plant crop the
return per rupee invested on labour is Rs 2.72 and on fertilizer is Rs 9.74. In
ratoon cane the return per rupee invested on labour is Rs 2.76 and on fertilizer
is Rs 9.11.
In conclusion, most inputs are required within 3—4 months. The factory has to
arrange for credit through commercial or cooperative banks. If cane supply is ex-
field, the factory arranges for harvest and transport. But if the cane supply is ex-
factory, the mill has to make advance payment for meeting the harvest and trans-
386
387
24 Economics of cane cultivation
port charges. For the cane cultivation to be profitable, timely input and timely operations are to be carried out. The mill should issue the cutting permits within 12-14 months so that maximum sugar and cane yields are realised with high profits. It is worth noting that the cost of producing one ton of plant crop is Rs 317 while that of ratoon crop is Rs 266.
Table 2 4 . 4 Operation-wise break-up of cost of cultivation for ratoon crop
Sugarcane in agriculture and industry
Fig. 24.1 Input-wise break-up of cost of cultivation of plant crop (Sundara, 1998)
Fig. 24 .2 Input-wise break-up of cost of cultivation of ratoon crop (Sundara, 1998)
388
Tissue culture
Tissue culture is a vegetative method for multiplying plants. It is also called plantlet culture or micropropagation/cloning. When plants are multiplied vegetatively all offsprings from a single plant can be classified as a 'clone'. Tissue culture simply directs and assists the natural potential within the plant to put forth new growth. Interestingly the history of tissue culture involves the entire history of botany, the origin of which is lost in antiquity. But P. R. White is acknowledged as the father of the tissue culture in USA. In 1939 he had cultured tomato and potato (Kyte and Kleyn 1996). Commercial tissue culture was first reported in the orchid industry in the 1950s. However it became clear that any plant would respond to tissue culture as long as the right formulae and right processes were adopted. It is also a good tool for specialists who hybridise plants by either sexual or asexual means. Often tissue culture is the most practical way to produce large numbers of plants required. It knows no seasons and plant propagation can be done throughout the year. Culturing plants needs no elaborate laboratory but requires a clean environment without contamination. It requires less space, less labour and less cost as compared to the other methods of propagation. Moreover most tissue culture plants are true to type, more vigorous and disease-free.
Test tube culture involves 4 steps: 1st stage—explant establishment or initiation, Ilnd stage—multiplication, Illrd stage—rooting, and IVth stage—acclimatisation or hardening. When new plant material is started in the culture it is grown in vitro (in glass). An explant is one piece of stem, leaf bud, root or seed meristem, or even one cell which can produce infinite number of plants.
Embryo culture, cell culture or callus culture fall under the broad term of tissue culture. Embryo culture can mean the 'rescue' of an embryo from a seed and fostering its plantlet development and multiplication in a culture. In other words, it is possible to culture embryos extracted from seeds (embryo rescue) or stimulate spontaneous production of embryos from undifferentiated cells; the process is called embryogenesis. In somatic embryogenesis embryos are induced to form somatic cells (vegetative or asexual). Cell culture is the cultivation of cells in solid gel medium or in a liquid medium; the latter is commonly known as cell suspension culture.
Callus culture is the multiplication of callus (a mass of disorganised, mostly undifferentiated or undeveloped cells) preferably on a solid medium. But Duncan (1997) states that the juvenile meristematic tissues are generally more efficient for
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Sugarcane in agriculture and industry
plant regeneration. But regenerated plant variability is higher among polyploid
and higher chromosome number explant sources such as sugarcane (Heinz and
Mee, 1969). Embryos may multiply and/or induced to form plantlets and the
process is morphogenesis.
The de-differentiated cells can also produce callus. Callus in tissue culture is in
fact a response to wounding. The callus mass can contain embryoids (embryo like
structures capable of developing into whole plants) or it can contain shoot or root
primordia. Callus can also develop cells with abnormal number of chromosomes.
Excision of explants stimulates the wound response 'in vivo' which can be en
hanced by growth regulators like 2, 4-D and 6-Benzylamino purine that have
been implicated in tissue culture induced variability (George, 1996a, 1996b).
Tissue culture competence may be due to the genes involved in hormone metabo
lism. Genes controling phytohormonal signals are directly involved in plant re
generation. Some cultivars may have genes that control tissue culture regenera
tion. Thus, the regeneration process includes reprogramming gene expression,
controlling differentiation of induced cells into embryos and maintenance of em-
bryogenic capacity. The ability to regenerate plants through long successive sub-
culturing is gene-controlled (loc. cit.).
Haploid culture is of practical significance. This is triggered by tissue culturing
of anthers or pollens to obtain haploids (cells with half the normal number of
chromosomes of vegetative cells). Haploid (n) plants are sterile but the chromo
somes duplicate and the plants will be diploids (2n). More so their progeny will
be true to form.
For the record, tissue culture offers a convenient method of handling mutants
(plants induced with mutant induced agents like radiation, UV light/carcino
genic chemicals). Following treatment, cultures are incubated and then tested for
certain characteristics, namely, resistance to toxins, salts, herbicides, antibiotics or
diseases, and tolerance to heat, cold, and other abiotic stresses. Of practical sig
nificance is their ability to synthesise secondary products/metabolites. The sec
ondary products potentially available from cell cultures include flavourings, pig
ments, medicinals, gums, resins, antibiotics, insecticides, fungicides, alkaloids,
enzymes, and oils.
Virus-free plants have been obtained in sugarcane from meristem culture and
the plants regenerated direcdy from explants or indirectly from callus may also be
virus-free (George, 1996b). The apical meristem is the new undifferentiated tissue
390
at the microscopic tip of a shoot. It is virus-free even in diseased plants. It also grows faster than the viruses. The cells from the apical meristem are removed from the plant and placed in a culture they can grow in and produce healthy, disease-free plants. This technique is known as meristem culture and often denoted as tissue culture/micropropagation. It is worth noting that new growth is initiated in meristem tissue which are undifferentiated cells that have not yet been programmed for their ultimate development. Meristematic cells are located at the tip of stem, roots in leaf axils, in stem as cambium, on leaf margins, and in callus tissue. According to George (1996b), in sugarcane callus could be initiated from the bases of leaves 1, 2, 3, and 4, preferably 1 and 2. This is expressly useful to select new sugarcane varieties with disease resistance, yield associated characters, sugar content and potential economic value. The medium commonly employed is Murashige and Skoog (MS medium) medium with minor modifications. The MS medium is supplemented with extra organic compounds, myo-inositol (100 mg H ) , thiamine—HC1 (1 g l -1), and casein -hydrolysate (400 mg l-1) for better shoot formation. Further confirmation comes from the work of Hendre and associates (1983) who demonstrated that sugarcane clones developed from meristem culture are very similar both pheno- and genotypically to the mother plant.
2 5 . 1
BASIC STEPS IN MICROPROPAGATION
The steps involved in micropropagation are depicted in Fig. 25.1. Essentially plant propagation by tissue culture is devoted entirely to the laboratory method of propagation. Plant material is taken from normal growing (in vivo) situation and culture 'in vitro' (in glass or clear plastic vessels). When plant material comes out of culture it is moved into ex vitro or extravitrum (outside glass) environment and must once again become adapted to normal in vivo growth. Thus tissue culture is a much more rapid method of vegetative multiplication.
25.2
MAJOR ADVANTAGES OF TISSUE CULTURE
1. In vitro techniques are valuable for storage and exchange of germplasm.
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25 Tissue culture
Sugarcane in agriculture and industry
Fig. 2 5 . 1 The basic steps in micropropagation
2. Mass multiplication: Once multiplication gets under way it could be expo
nential. One should expect the plants more than double each time they are
transferred. A single explant would give 1024 plants after 10 months and
2048 plants after 11 months. The multiplication rate in sugarcane is given
in Table 25.1 (Hendre et al., 1983).
T a b l e 2 5 . 1 Multiplication rate in vitro culture
Source: Hendre et al., 1983.
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25 Tissue culture
The authors conclude that in about 4 months, 200,000 rooted plants are
obtained with 80% survival. The space required for producing 200,000
plants per year is 165 m2.
3. Utilization of minimum plant material: Cultures are started with very small
pieces of plants (explants) and thereafter small shoots or embryos are propa
gated. This is important in sugarcane when 7—8 t ha - 1 seed material is used
for plants which can otherwise be used for milling.
4. Elimination of pathogens: Propagation is ideally carried out in aseptic condi
tions free from pathogens. Plantlets finally produced should be free from
bacteria, fungi and other microorganisms. Certified virus-free plants can be
produced in large numbers.
5. Rapid production of plant material: The rate of propagation is much greater
than in macropropagation. This is ideally suited for newly released varieties
in sugarcane where plant to seed ratio is 1 : 10 or 1 : 12.
6. Multiplying plants that are difficult to propagate vegetatively: It would be pos
sible to produce clones of some kinds of plants that otherwise are slow and
difficult (even impossible) to propagate vegetatively.
7. Clonal multiplication and uniformity: The clones can be multiplied without
any difficulty. The developed plantlets would be completely uniform.
8. Somatic hybridization: Hybrid plants can be developed by fusing protoplasts.
9. Tissue culture. Methods facilitate genetic engineering of plants. The tissues
like single cells, callus or any other plant material can be treated by
transformants and later they can be subjected to tests for evaluating genes
incorporated in vitro.
10. Natural alkaloids: Many secondary metabolites are of research value or
commercial importance such as pharmaceuticals, medicines, dyes, food
additives, natural flavours, fragrances, gums, and pesticides. The products are
conventionally extracted from a whole plant or parts of plants. Traditionally
the plants are field grown or they are collected in the wild where they are often
in short supply, limited by season and weather. The yield is unpredictable and
of questionable quality. The collection and removal can lead to extinction.
The application of plant tissue culture to growing cells, callus or plantlets for
the purpose of extracting secondary products is gaining importance.
11. Cryopreservation: Growing and maintenance of 'field gene banks' is an up
hill task. In vitro conservation of plants or cryopreservation is an alternative
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Sugarcane in agriculture and industry
solution for the long time storage of cultures without changing the genetic
constitution.
2 5 . 3
RAPID MULTIPUCATION OF SUGARCANE BY TISSUE CULTURE
The formation of callus tissue in Saccharum without differentiation of plants was first reported from Hawaii (Heinz and Mee, 1969). Roots and other organ -like structures were formed only when dolopon was added to the medium in which the callus was growing. The most rapid formation of callus tissue occurred on the basal medium containing 3 ppm 2, 4-D and coconut water. Heinz and Mee (1969) reported that the apices of shoots leaves and inflorescences formed callus within 2-4 weeks of explantation. Further the callus from H37—1993 cultivar developed both roots and shoots on the medium whereas callus from H5 Q-7209 developed shoots with nominal roots. According to them differentiated plants were transferred to water culture for further development of roots and then potted in vermiculite for subsequent growth.
Hendre et al. (1983) have reported that 8-month-old canes of Cv Co 740 were selected and shoot apices were brought to the laboratory. Stem segments (15—20 mm) containing meristem were excised and first rinsed with water containing a detergent, and then treated with 30% of a saturated chlorine water solution for 20 minutes. At each step the explants were washed thoroughly with sterile water. Dissection of the individual segments was then carried out in a sterile cabinet. The shoot tip (2-3 mm) containing the meristem dome and 2—4 leaf primordia were inoculated into the tubes containing 20 ml of liquid basal media. Two main media were used, one for shoot elongation and the other for shoot multiplication.
George (1996b) confirms that callus cultures are readily obtained from explants excised from young expanding leaves, immature inflorescences, young roots, and sections of stem near the growing point. The commonly employed medium is Murashige and Skoog medium (MS medium) with minor modifications. For callus initiation myo-inositol (100 mg 1_1) and thiamine—HCl (1 g H) are added. For shoot regeneration, casein hydrolysate (400 mg I-1) is added to the medium. It is safely recommended to supplement MS medium widi extra organic compounds.
Hendre et al. (op. cit.) asserted that the MS medium (MS-I) must contain mineral salts, vitamins, coconut water (5%), gibberellic acid (0.1 mg 1-1)> and
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25 Tissue culture
indole-3 butyric acid (0.01 mg 1_1) for effective shoot elongation. The medium for shoot multiplication (MS-II) also contains all mineral salts and vitamins, but is supplemented with 0.1 mg l - 1 Kinetin (K), 0.2 mg l-1 benzyl aminopurine (BAP) and 10% coconut water. The rooting medium contains salts and vitamins and is supplemented with 0.2 mg l""1 of sodium molybdate and copper chloride. All media are sterilized by autoclaving at 15 psi pressure for 20 minutes and steamed for 30 minutes the next day.
T a b l e 2 5 . 2 Field data on clonally propagated sugarcane plants
Parameters
Plot size (m) 1 1 x 1 1
Spacing (m) l x l
No. of plants sown 83
Height of millable canes (m) 2.64
Number of canes per clump 18
Number of internodes per cane 30
Weight of individual canes (kg) 1.24
Number of canes per plot 1494
Source: Hendre et al., 1983.
Shoot tips (2—3 mm) after dissection were inoculated into tubes containing
20 ml of liquid MS-I medium. It has been reported by many that virus-free plants
can be obtained from meristem culture and plants regenerated directly from
explants or indirectly from callus may also be virus-free. Thus cultures were incu
bated in a growth chamber at 20 °C with a 12-hour photoperiod of light intensity
800-1000 lux. After 15-20 days individual elongated shoot tips were transferred
to conical flasks containing 20 ml liquid MS—II medium. After another 15 days,
the shoot tips elongated and attained a height of 45-50 mm. Thus multiple shoots
were formed in the flask but did not develop roots. They were healthy. For root
initiation the shoots were separated individually and inoculated into the tubes
containing 20 ml rooting medium and supported on a filter paper platform. Within
15 days, a healthy root system with root hairs was formed. A few plants also
developed tillers. The rooted plants were washed with water, the adhering me-
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Sugarcane in agriculture and industry
dium was removed and the plants were then transferred to pots containing 1 : 1 mixture of sterile soil and vermiculite. Individual plants were covered with beakers to maintain humidity and were kept for hardening at 25 °C under a light intensity of 800—1000 lux for two weeks. They were then transferred to a glass house. When they attained a height of 7—10 cm, they were transferred to the field where their survival rate was 80% (Hendre et al., 1983). The authors claim that about 200,000 plants can be obtained in 6 months which is sufficient for planting 10 ha at a population density of 20,000 plants per ha. Field data showed that clonally propagated plants were uniform with respect to height, number of internodes, millable cane population, and weight per cane (Table 25.2).
It is inferred that this method could be highly valuable in sugarcane breeding programmes for rapid multiplication of newly released varieties.
Box I
Tyndallization
The process of sterilization is called Tyndallization (after John Tyndall).
It is a tool useful for tissue culture in that it helps to determine the best
method of sterilizing media for growth of certain cultures. Through
tyndallization one can determine if it is preferable to use the boiled me
dium or a med ium more conventionally sterilized in an autoclave.
Autoclaving can cause problems because certain chemicals will degrade or
change under heat or pressure. Tyndall also constructed a chamber, die
first recorded forerunner of present day tissue culture hoods. These are
boxes or chambers in which cultures are transferred aseptically.
25.4-
SOME TERMINOLOGIES
(Source: Kyte and Kleyn, 1996)
1. Anther culture: In vitro cultures of anthers to obtain haploid plants.
2. Artificial seed: A somatic embryo that has been coated or encapsulated and
grown as true seed.
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25 Tissue culture
3. Bridge: A piece of filter paper or other device placed within a test tube of
liquid medium to hold the culture out of the liquid. Also known as rafts or
floats.
4. Callus: A proliferating mass of disorganised, mostly undifferentiated or un
developed cells.
5. Callus culture: The multiplication of callus cells in sterile culture.
6. Cell culture: The multiplication in vitro of single cells or clumps of cells not
organized as tissues, often included in the broad term 'tissue culture'.
7. Cell suspension culture: The culture of single cells or clumps of cells sus
pended in a liquid medium.
8. Embryo culture: In vitro culture of embryos excised from seeds or embryos
induced to form from somatic cells.
9. Meristem: Denotes microscopic shoot tip, usually under 1.5 mm and con
taining one or two leaf primordia, used as explant.
10. Meristem culture: In vitro culture of meristematic tissue; also misused more
broadly to denote micropropagation.
11. Micropropagation: Propagation on a very small scale. Vegetative multipli
cation in vitro. It is used interchangeably with the terms 'tissue culture' or in
vitro culture.
12. Mycorrhiza: A fungus that associates usually symbiotically with plant roots.
13. Organogenesis: The formation of organs such as leaves, shoots, or roots
from cells or tissues.
14. Secondary product: A product of plant metabolism that is not primarily
related to growth and reproduction, such as medicinals, flavourings, dyes,
pesticides, etc.
15. Somatic embryogenesis: The formation of embryos from somatic cells.
16. Sport: A plant or plant part that has undergone mutation.
17. Stages of culture: Stage — establishment, Stage II—multiplication, Stage
III—rooting, Stage IV—acclimatization.
18. Tissue culture: Literally, the culture of individual tissues but usually used
more broadly to indicate micropropagation or in vitro propagation.
19. Totipotence: The capability of a cell to develop into a whole plant.
20. Transfer chamber or hood: A protected, enclosed area with a sterile atmos
phere in which cultures are started, divided, trimmed, and then transferred
using sterile technique.
397
1 What ails the sugar industry?
Two or three years of surplus sugar are followed by an year of acute shortage of
sugar in the country. In fact it is a surplus-shortage merry-go-round. The industry
is in a state of flux and needs a pragmatic approach to come out of the snafu.
Some fire-fighting approaches are made but no long-term measures are in sight.
The author admits that it is not possible to reduce the complex issues of the sugar
industry into 'one-liners'. The major causes which make the industry sick are:
i) Full capacity utilization is not made. The industry should run for a minimum
period of 180 days in subtropical India and 240 days in the tropical belt,
ii) High initial capital cost for machinery and spares,
iii) High sugar conversion cost due to high cost of chemicals,
iv) High cost of raw material. The price of sugarcane is much higher than the state
advised price. There is an urgent need to reduce unit cost of production by
vertical yield expansion, i.e. yield per hectare needs to be doubled. A 12/13-
month crop is more profitable than the adsali crop (18 months). Leguminous
intercrops not only provide additional revenue but also help in sustainable high
production. Biomass diversification includes planting of trees such as Casuarina,
Sesbania, and Acacia, as border rows. This is a vital part of agro-forestry. These
trees have 'open canopy' and do not adversely affect the yield and quality of the
cane. They also provide fodder and fuel besides reducing the lodging of cane.
Cordage crop like Mesta {Hibiscus cannabinus) and Roselle (H. subdarijfa) of
the Malvaceae family can also be grown as strip crop/intercrop to provide excel
lent fibre. It is a total substitute for bamboo and mesta/Kenafpulp can be blended
at 2 5 % to manufacture newsprint and other special papers.
v) Exorbitant project costs for expansion and new installations, the imposition of
duties and government control on sales makes the industry financially nonviable,
vi) The production cost of sugar in India is very high and hence our sugar indus
try cannot compete in the international market.
Diversification of sugarcane to produce value-added products such as paper,
biofuels, cogeneration of power, etc. (valued at US$ 8000 per ton of raw material)
would make the industry economically viable and sustainable.
So sugar-paper-alcohol-power complexes can be established to produce myriad
products of commercial value. Manufacturing life-saving drugs like human insu
lin (to name just one) from sugarcane would be first in the list of priorities. Sugar-
paper-alcohol-power complexes would also serve as a nucleus in rural areas for
rapid socio-economic change.
398
Processing of sugarcane into white sugar B. S. Gurumurthy, Sugar Technologist, Bangalore
A major portion of the sugar in the world is produced from sugarcane although sugar beet is also used as raw material for the manufacture of sugar in certain parts of the world. The use of sugarcane for the manufacture of sugar is said to have been known to mankind even in the Vedic days.
Sugarcane is generally about 70% water, 15% fibrous material and the balance is dissolved solids. While the detailed analysis of the constituents of cane does not come under the scope of this chapter, the approximate analysis is given below.
Sugarcane 100%
Water 70 to 7 3 %
Fibre 12 to 15%
Sugar 12 to 14%
Dissolved non-sugar solids 2 to 3%
In extreme cases there would be even wider variations, depending upon the age
and varieties of cane and also the climatic factors like temperatures, humidity, etc.
The processing of sugarcane obviously should incorporate efficient steps to
extract the sugar while eliminating the water, fibre and the non-sugar solids. It is
again obvious that at each stage of the process while the other constituents are
eliminated, they carry a certain amount of sugar also. Hence the process has to be
designed to keep at a minimum the sugar losses occurring through the exit of
water, fibre and the non-sugar solids.
As mentioned earlier, sugarcane has about 70% water; the entire quantity of
water has to be evaporated expending a huge quantity of steam. This process
needs to take into consideration the various steps to be incorporated for achieving
maximum economy in the use of steam. Modern sugar factories have updated
their technology not only to produce better quality sugar, but also to improve the
efficiency to extract more sugar from the available sugar in the cane. Modern
sugar mills also adopt energy efficient technologies and systems to generate sur
plus power and sell the same using the same available fuel, namely, bagasse. Equip
ment designs have also improved for achieving the above.
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Sugarcane in agriculture and industry
The water evaporated during the process of sugar manufacture is condensed back and collected at different stages and recycled beneficially, thereby reducing the intake of freshwater and also minimising the generation of liquid effluents.
Following are the main unit operations involved in manufacturing sugar from sugarcane:
1. Extracting of juice from sugarcane
2. Clarification of cane juice
3. Evaporation of water 4. Crystallisation in vacuum pans 5. Crystallisation in motion
6. Centrifuging
7. Sugar drying, grading and packing and storing
2 7 . 1
EXTRACTION OF JUICE FROM SUGARCANE
The sugar (sucrose) in cane is in the dissolved state and hence in the form of juice.
The juice containing in it both sugar and non-sugar solids is held tight inside
millions of tiny cells spread across the cross-section of the sugarcane.
For extraction of the juice from cane it would be necessary to rupture or break
these cells. Heavy duty preparatory devices, consisting of a number of rotating
knives with hardened edges are used to prepare the cane. Generally two or three
such sets of knives are used. These knives not only cut and disintegrate the cane
into smaller and thinner pieces, but also rupture and open the cells holding the
juices to facilitate easy and better extraction of juice.
27.1.1 Mi l l ing
The cane prepared as above is passed through a series of mills for extraction of
juice. The mills generally consist of three rollers with grooves, two rollers being
placed below and the third roller on the top of the two bottom rollers. The pre
pared cane is passed through these rollers. A heavy hydraulic load is applied on
the top roller and the prepared cane is pressed while passing through twice be
tween the top and the two bottom rollers. The juice extracted flows down the two
bottom rollers through the grooves and is collected in the gutter placed below the
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27 Processing of sugarcane into white sugar
mills. It is a normal practice now to install one more roller called underfeed roller which facilitates uniform and good feeding of prepared cane into the mill.
Generally there would be 4 to 6 such mills in the milling tandem depending upon the desired capacity and size of the mill rollers. The prepared cane is passed through all the mills one by one in succession to complete the extraction process.
The size of the mill is generally expressed by the roller length and diameter, and decided depending upon the desired installed capacity. For example, a milling tandem designed to crush about 100-120 tons cane/day would have rollers of size 900 mm dia and 1800 mm length and four mills, each of three regular rollers and one underfeed roller. The crushing capacity can be increased by 50% by adding two more similar mills to the tandem. Beyond six mills in the tandem is not found useful and hence any further increase in capacity should be considered only with increase in size of the mill rollers.
27.1.2 Imbibition
When the prepared cane is crushed in the mill, the juice so extracted flows down
through the roller grooves and the residue which is called 'bagasse' comes out of
the discharge roller which is guided to the next mill for successive extraction. The
bagasse coming out of the mill would have been substantially exhausted of the
juice and would be partially dry. This bagasse is made wet by adding dilute juice
or water before subjecting it to successive crushing in the next mill. This process
is called imbibition.
To avoid the use of too much of water (which will have to be evaporated in
processing subsequently), the addition of water is restricted to only before last
mill. The dilute juice from the last mill is used for imbibition before the penulti
mate mill and so on. Hence the dilute juices are recycled in the counter current
direction. The concentrated juice from the Mill-I is called primary juice and the
juice coming out of the Mill-II is called secondary juice. Both these juices are
mixed together (mixed juice or raw juice) and sent for further processing.
Often, hot water at a temperature of 60 °C to 70 °C is used for imbibition to
improve the extraction. Higher temperatures than the above have shown better
results in terms of extraction, but pose problems like polishing up rollers and
causing slippage. Very high temperatures are said to have caused higher wax ex
traction resulting in problems in clarification of juice. About 60 °C is generally
found to be optimum.
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Sugarcane in agriculture and industry
The quantity of water added is normally decided as a compromise between the
extraction of sugar and the cost of evaporating the added water. Higher the water
addition, higher is the recycling of dilute juices for imbibition in the penultimate
mills and higher is the extraction of sugar in all the mills after the Mill-I in the
tandem. The extraction in the Mill-I is directly proportional to the degree of
preparation of cane (the degree of opening of cells).
The incremental extraction due to imbibition depends not only on the quan
tum and the temperature of water, but also on the method of application of the
water on the 'bagasse mat' coming out of the mill. Different engineers use differ
ent application methods depending upon the conditions to achieve good results.
However, whatever method is used, the objective is to achieve a good admixture
of water into the bagasse and preferably to allow some time after the addition of
water, before subjecting it to crushing in the next mill. Uniformity in application
in proportion to the bagasse flowing is also an important factor. Generally it is
believed that more water is needed to be added in case of cane with higher fibre
content. Hence internationally the practice is to measure the added water in terms
of "added water percent fibre". The author is of the opinion that the added water
must also be in proportion to the sugar content in the prepared cane or in the
bagasse. Higher sugar or higher concentrated cane juice entering the mill needs
more water to be diluted to maintain a uniform residual sugar level in the bagasse.
The added water quantity is linked with the fibre content probably with the as
sumption that the fibre-juice ratio is maintained constant in the mill after extrac
tion. But the factor of concentration of the residual juice is ignored. A higher
concentration of juice needs higher added water for dilution.
In practice, all over the world the added water is generally fixed on cane and/or
fibre. The modern practice is to add water to the extent of 300% fibre, which is
generally accepted as a balance between extraction and the cost of evaporation of
added water.
Addition of imbibition water is often determined by the concentration (brix)
of the last expressed juice (the juice that is coming out of the discharge roller of
the last mill.) Depending upon the operating conditions, evaporation capabili
ties, and the primary juice concentration, the mill engineer fixes his own standard
for the brix of the last expressed juice. Whatever the parameters that are followed,
the ultimate objective is to achieve as low a sugar content as possible in the final
bagasse.
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27 Processing of sugarcane into white sugar
Besides good preparation of cane and optimum imbibition water, certain other factors also affect the efficiency of the operation of the milling tandem (Milling operation). These are briefly mentioned below.
Mill feeding
The feeding of the prepared cane into the mills should be uniform and to the full capacity of the mills. To facilitate optimum and uniform feeding, the individual mills are equipped with additional facilities like Doneilly Chutes (a positive feeding device) and also pressure feeders. While the Doneilly chute offers a positive head, the pressure feeders help forced feeding into the mill. Doneilly chute also helps to maintain uniform feeding across the roller width.
The pressure feeder is nothing but an additional roller either grooved or teethed. The diameter of this roller varies from 60% to 100% of the diameter of the mill rollers. The pressure feed rollers are generally called underfeed rollers. The underfeed roller together with the Doneilly chute will facilitate a uniform and optimum feeding rate.
Roller arching
During the course of continuous working, the roller surface gets polished causing
slippage and reduced 'grip' of the rollers on the bagasse mat. To counter this
effect, the tips of the roller grooves are roughened at frequent intervals by 'arch
ing' of the tips of the roller grooves. Special welding rods are available for this
purpose. Arching will improve the grip. The frequency of the arching depends
upon the roller polishing which depends upon the temperature of imbibition
water, wax content in the cane, crushing rate, etc. All the rollers are arched while
installing and also during shutdowns, etc. The underfeed rollers, top rollers and
often discharge rollers are arched even while running, if necessary.
Hydraulic load
The top roller on each mill is provided with a floating arrangement and a hydrau
lic system which applies pressure on the top roller uniformly on both ends. The
arrangement has a facility to increase or decrease the hydraulic load on each mill.
The hydraulic load helps in improving the mill extraction. The load factor is
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Sugarcane in agriculture and industry
decided by the mill engineer taking into consideration the desired rate of crush
ing, extraction, and applicable load on each mill. Normally the load applied on
the top roller is about 200 ton/metre of roller length.
Mill grooves
The rollers are grooved to achieve a good grip on the cane or bagasse mat. Groov
ing also helps in better squeezing because of the differential surface speed across
the surface of the grooves. Further the grooving helps drainage of the extracted
juice. All the above factors will together help maintaining optimum crushing rate
and extraction level.
The size and type of grooving are an individual engineer's choice. A number of
options are available with regard to depth and angle of the grooves. Often differ
ential angle groovings (different angles for top and bottom rollers) are also used.
The selection of the grooving size and angle is a compromise between the crush
ing rate and the efficiency. Generally deeper and wider groovings are preferred for
achieving higher rate of crushing. Also the grooving size is required to be bigger
(deeper and wider) in the primary mill; it reduces towards the last mill. The grooving
size also increases with the increase in diameter of the rollers.
Mill settings
The gap between the rollers which is set by the engineer, and can also be adjusted as desired, plays a significant role in achieving the crushing capacity and efficiency. The power consumption by each mill also varies with the settings. Different settings are set between the top and feed rollers, the top and discharge rollers and the top and trash plate (a specially designed plate fitted between the feed and discharge rollers for conveying the prepared cane or bagasse forward from the feed roller to the discharge roller). The settings also vary from Mill-I to the last Mill. Wider settings are necessary for the first mill and would have to be narrowed down towards the last mill gradually. Similarly feed roller gaps are set wider than discharge roller gaps and the trash plate gap is even wider. All the openings (settings) between the rollers and trash plate are to be set with some proportions and ratios to be decided by the mill engineers.
There are certain mill designs, where the ratios between the openings are maintained constant (constant ratio mills)
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27 Processing of sugarcane into white sugar
Mill speeds
The speed of the mill is judiciously fixed often as a compromise between the rate of crushing and efficiency. Higher speed permits higher rate of crushing whereas lower speed facilitates more contact time, better squeezing and better drainage of juice, and thereby helps improving the efficiency. At the same time increasing the speed beyond a certain limit will increase the slippage and it becomes counterproductive. Generally the roller speed is fixed at 4 to 6 rpm depending upon the roller size, groovings, crushing, rate, number of mills in the tandem, etc. Often the speed is also measured in terms of the peripheral speed of the rollers and about 12 to 15 m/minute is maintained.
Mill performance
The milling tandem has two performance parameters—crushing rate and efficiency. In addition to these, the power consumption is also significant. Hence the overall performance of the milling tandem is judged by the rate of crushing and also the efficiency in terms of juice extraction percentage at optimum power consumption. As the crushing rate has to match the capacities of the sugar processing house, each milling tandem is designed to handle a certain rate of crushing that is fixed as optimum capacity.
Generally operations are to be directed to achieve maximum efficiency of the mill in terms of juice extraction or in terms of keeping the sugar loss in bagasse as low as possible.
If the operating parameters like preparation of cane, uniform and optimum feeding, hydraulic load on rollers, mill speed, imbibition rate, and admixture are at an optimum level, the sugar content in the final bagasse would be minimum. This will ensure maximum efficiency in terms of extraction.
The mill extraction is expressed as the sugar extraction in mixed juice percent sugar in cane.
Mill extraction = (sugar in mixed juice % cane /sugar percent cane) x 100
The operating conditions being uniform the mill extraction varies with vary
ing fibre content. Hence for comparison between the performance of different
mills, the actual mill extraction is reduced to a standard figure calculated on the
basis of a standard assumed figure of 12.5% fibre. This is called reduced mill
extraction.
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Sugarcane in agriculture and industry
Similarly it is also found that the operating conditions being the same, the mill
extraction varies with the sugar content in the cane. Hence a similar standard for
sugar content in cane is also set at 12.5% and the actual mill extraction is reduced
to standard mill extraction on the basis of 12.5% sugar in cane.
During normal operations the milling efficiency is measured only by the sugar
(pol) percent in bagasse. The moisture in bagasse is also another factor affecting
the efficiency. Higher moisture in bagasse indicates higher juice going out in ba
gasse and higher sugar. The bagasse is analysed for sugar and moisture content
every four hours during operation, whereas the mill extraction is calculated only
once at the end of the day.
For more frequent monitoring the brix of the last expressed juice is analysed
every hour as this is a simpler and less time-consuming analysis.
For a more detailed study, particularly when the desired results are not achieved,
a study is made of the performance of individual mills and also of the individual
rollers (feed and discharge) by plotting brix curves. A critical study of the brix
curves will indicate which of the mills in the tandem is inefficient and further
study will reveal which of the rollers, whether feed or discharge is inefficient.
Generally a slight adjustment in the settings will remove the defects.
Similarly the brix analysis of the juices from individual rollers and the com
bined juice of any particular mill will help in working out the proportion of juice
extraction from each roller and assessing the imbibition efficiency-—the degree of
admixture of imbibition water or juice with the bagasse mat. Normally, the ex
traction in the feed and discharge rollers is in the ratio of 3 : 1. A ratio of 0.8
between the brixes of feed roller juice and the combined juice, and a ratio of 1.2
between discharge roller juice and the combined juice indicate good performance
of any particular mill.
The poor performance of any particular mill if indicated on both the feed and
discharge sides would generally be attributable to inadequate or improper hy
draulic load (unless all the settings are open more).
A good milling performance needs good cane preparation followed by primary
extraction. The preparation of cane is measured by the preparatory index which
indicates the percentage of broken cells in the prepared cane. With modern heavy
duty preparatory devices, a preparatory index of 80 and above is achieved.
The primary extraction is calculated by analysing the primary bagasse for sugar
and moisture contents. The primary extraction is also calculated by analysis of the
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27 Processing of sugarcane into white sugar
brixes of primary juice, secondary juice, and mixed juice. The primary extraction indicates the sugar extracted in primary juice percent sugar in cane. A good primary mill with good preparatory index will yield a primary extraction of about 80%.
Mill drives
The earlier practice was to run the mills with steam turbines through a reduction gear system. This is followed by most sugar mills even today, they being earlier installations. To save initial investment and also the maintenance cost, normally one turbine would run two mills with appropriate gearing arrangements. Of course, in bigger size mills individual turbines are installed. But being smaller in size, the turbines are essentially single stage turbines and less efficient as compared to multi stage turbines.
The modern practice is to generate electricity using thermal efficient multistage turbines in a central power house and adopt electrical drives for all other applications. This system improves the overall thermal efficiency, thereby making available surplus thermal energy which is gainfully employed for generation of surplus power as a by-product.
But still, the turbine as mill drive has been very popular because of its advantages like trouble-free running, simplicity of operation, ease of speed control, capacity to absorb impact loads, flexibility to handle variable loads, h igh starting torque, etc.
Nowadays, with the idea of generation of surplus power catching up, more emphasis is laid on energy efficient equipment and technologies. Mill drives being the major power consuming units, attracted the special attention of the engineers for application of more efficient drives for mills.
Development of electronic technology for conversion of AC power to DC power gave rise to the use of DC motors to run the mill as mill drives which facilit?ted variation of speed as easily as in turbines. Further in case of DC motors the speed reduction stages are less and instrumentation is easier. Use of DC motors for mill drives facilitated installation of large size multi-stage efficient turbines in the power house and running of all other drives on electrical power, thereby introducing a high level of efficiency and enabling generation of substantial quantity of surplus
power. Lately, DC motors are being replaced by hydraulic motors. The hydraulic drive
system primarily consists of a power pack with very high pressures of 20O-300 bar.
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Sugarcane in agriculture and industry
The pressure is transmitted through oil to the hydraulic motors mounted directly on the mill rollers. The system makes redundant the entire gear system thereby avoiding the power loss due to transmission. This system saves place, and makes maintenance simple and cheaper. Even the tail bar can be avoided. Opinions of engineers differ with regard to power saving as compared to DC motors. Power consumption per ton of fibre has not shown any significant saving in certain installations of hydraulic drive; however, there is no second opinion regarding the saving in place, civil cost, and simplicity in maintenance.
Low pressure mill
Basically the mill consisted of only three rollers—top, feed, and discharge rollers,
with two pressings. Subsequently, underfeed rollers were added to improve feed
ing although this increased power consumption. There are examples of two un
derfeed rollers with extraction also. There are a few examples of three rollers prior
to the original mill. Here there is one inverted mill over the mill. Each mill con
sists of six rollers. While such arrangements may help the expansion of existing
units, the system becomes very complicated posing serious maintenance prob
lems. The power consumption also increases in this system as there would be
substantial power loss in the movement of the bagasse mat between the rollers.
A new system called 'low pressure milling' is under experimentation. Instead of
multiplication of rollers in a single mill, there are only two rollers in each mill
without any trash plate; and there are a series of such mills in a tandem. In this
system, imbibition plays a more significant role, and the pressure plays a com
paratively lesser role, thereby making the extraction process more refined. Only in
the last mill there are three rollers for dewatering or reducing the moisture.
The two-roller-milling system has a number of advantages like energy saving,
absence of trash plates, saving in power, and simplicity in maintenance.
Mill sanitation
From the time the cane is harvested, it is exposed to the attack of the microorgan
isms. Many types of microorganisms are found to be present in the cut cane. It is
desirable to crush the harvested cane with least loss of time. The microorganisms
cause inversion of sugar and thus deteriorate the cane. The rate of deterioration
increases with time.
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27 Processing of sugarcane into white sugar
In the milling station these organisms multiply and cause loss of sugar. Further the inversion of sugar brings down the pH of the juice, thereby promoting chemical inversion. If unchecked, the losses would be enormous. The attack and growth of microorganisms in the milling stations are arrested by treatment with biocides. Different biocides are used for this purpose. Often chemicals like sulphur dioxide and ammonium bifluorides are found effective and inexpensive. Many branded chemicals and biocides are available which are very effective but expensive. These chemicals are added in the form of a dilute solution, continuously, preferably at two points—at last mill juice gutter and secondary juice gutter. The microorganisms get killed in the process when the juice is subjected to high temperatures.
However there is no substitute for good housekeeping in the mill station. The entire mill house is to be washed at least once in 4 hours either with steam or hot water—preferably with a jet of hot water. The bagasse and bagacilo accumulation in nooks and corners in the mill house would become an ideal home for the growth of microorganisms. Hence a good wash with a jet of hot water will minimise the growth. The leaks of juice and the stagnation of sugar bearing materials in the entire factory should be avoided, to avoid the growth of microorganisms.
Proper housekeeping and mill sanitation are very important and significant and if neglected may lead to substantial sugar loss in addition to creating serious process problems.
27.1.3 Juice weighing
The weighing of juice has a significance, in the sense, that it helps to know how much sugar has been extracted into juice from the given quantity of cane (from the given quantity of sugar in the cane). This enables the working out of the actual mill extraction every day or in any given time.
Further it also enables working out of the process efficiency. The mixed juice becomes the input into the process. The sugar produced out of the sugar present in the given quantity of mixed juice indicates the efficiency of the boiling house.
27.2
CLARIFICATION PROCESS
The cane juice as extracted from the mill contains about 85% water. It may be a little less or a little more depending upon the quantity of added water used in the
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mill. It contains about 1 1 % to 13% sugar and about 2 to 3% of dissolved non-sugar solids. Besides it contains suspended impurities to the extent of 0.3 to 0.4%. It will be in the form of a turbid greenish liquid with a pH about 5-5.
The objective of clarification is qualitative rather than quantitative. The clarification should result in a juice which is neutral (pH 7.0), clear and transparent, with a light colour. During the process, all the suspended impurities are eliminated, most of the colouring matter is removed, some of the non-sugar solids are precipitated out and removed by settling, while the sugar (sucrose) and the reducing sugars (glucose and fructose) are kept intact. Hence the functions are many. A number of physical and chemical reactions are involved in the clarification process. A detailed discussions on the reactions involved is beyond the scope of this book.
An attempt is made only to present a brief description.
The process followed depends upon the quality of the final product. Generally two types of sugar are manufactured in a sugar factory: (1) raw sugar (2) white sugar (direct consumption white sugar).
27.2.1 Clarification process for manufacturing raw sugar
The raw sugar is manufactured as an intermediate stage for producing refined
sugar. The refined sugar is a finer quality sugar with lesser impurities, slightly
brighter in colour when compared to white sugar. The raw sugar is sent to refiner
ies where it is subjected to a refining process to produce refined sugar. Thus raw
sugar is not as pure as white sugar. It contains a thin film of molasses embedded in
the crystals. T h e clarification of juice for producing raw sugar also differs from
that followed for white sugar manufacture. The raw sugar is slightly brownish in
colour not only due to the molasses content but also due to the fact that the juice
clarification does not involve sulphur dioxide gas a bleaching agent.
Defecation process
This process is used especially for the production of raw sugar. It is very simple; the juice is heated to about 70 °C, and calcium hydroxide in the form of milk of lime is added to the heated juice to raise the pH of the juice from about 5-5 to 7.6—7.8. After a few minutes retention period, the treated juice is again heated to 100 °C+ and pumped into a continuous clarifier. A retention time of about 21/2 to
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27 Processing of sugarcane into white sugar
3 hours is given in the clarifier during which time the precipitated flocks settle down. The clear transparent juice is decanted for further processing. The sediment from the bottom is pumped through a rotary vacuum filter. The filtrates are re-circulated back into the process and the filtered mud is thrown out. The filter mud is used as organic manure in the fields. The filtrates are generally re-circulated by mixing them either with mixed juice or treated juice. The clear juice goes to evaporators for concentration.
During heating and addition of calcium hydroxide, and again heating, a number of calcium salts are precipitated, the predominant salt being calcium phosphate. If the cane juice is deficit in phosphate content, that is made up by additions of phosphate, either in the form of phosphoric acid or super phosphate solution. Phosphate in the mixed juice ensures formation of calcium phosphate flocs which absorb and adsorb colloidal particles and small precipitates, resulting in better and faster sedimentation and clearer juice.
Certain polymeric compounds are used in small doses as settling aids—being added to the juice just before it enters the clarifier. These chemicals aid quicker settling and also help in sedimentation of the colloidal particles.
27.2.2 Clarification process for manufacturing white sugar
White sugar demands a better degree of clarification. More impurities, particularly colouring matter, need to be eliminated in the clarification process. Besides, the juice needs to be treated with some bleaching agents which remove colour partially, making the resultant clarified juice light coloured and transparent.
The agents used for clarification are heat, milk of lime (calcium hydroxide), sulphur dioxide gas, phosphoric acid, etc. Use of carbon dioxide gas is also in vogue in some old sugar mills as bleaching agent in place of or in addition to sulphur dioxide gas. However most, factories which are using carbon dioxide are slowly abandoning the process and changing over to sulphur dioxide. Hence the use of carbon dioxide is not dealt with here.
Double sulphitation process
This is the standard process followed in all most all sugar factories manufacturing direct consumption white sugar. Recently there has been some opposition to this process with claims that there would be remnants of sulphur in the final product
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Sugarcane in agriculture and industry
—direct consumption white sugar. However, it is found that with proper care
taken during the process, it is possible to maintain the sulphur content in the final
product within the permissible limit.
This process is one of the cheapest and simplest and is ideally suited for devel
oping countries. The improvement achieved in terms of purity by the refining
process over the direct consumption white sugar is very marginal, but the refining
process is very expensive and the high cost is not justified except where higher
purity sugar is preferred like in pharmaceuticals, soft drink industry, etc.
The double sulphitation process is followed in different permutations and com
binations, like cold liming, hot liming, pre-liming, pre-sulphitation, etc. Only
the most common practice is explained below.
The juice after weighing is heated to about 70 °C in juice heaters and then
subjected to simultaneous liming and sulphitation in a treatment tank. Normally
the juice enters the tank through a scrubber placed above the tank so that the juice
scrubs off the excessive S 0 2 gas escaping from the tank. Then the juice is guided
to the bottom of the tank through a fairly large diameter pipe during which the
milk of lime is added. At the bottom of the tank there is a network of pipes
through which S 0 2 gas is bubbled. Thus the juice is first limed and immediately
after, it is sulphited. Some technologists prefer to add milk of lime and S O . gas
simultaneously at the bottom of the tank. The exact point of addition of milk of
lime is the choice of individual technologists. However the most preferred prac
tice is to increase the pH first to about 8.0 and then sulphite to about 7.2 p H ,
leaving a time gap of a few seconds between liming and sulphitation. In the case
of refractory juices, the liming is done even beyond 8.0 pH to achieve good clari
fication. In such cases the consumption of lime and sulphur increases. Thus the
quantity of lime and sulphur used depends on the initial pH to which the juice is
raised from its original pH , which again depends upon the quality of juice, and
sometimes upon the decision of the technologist. Very high pH, often, results in
darker coloured juice though of good clarity, and also in harder scale formation in
die evaporator vessels in subsequent boiling.
It is a general practice to control the pH of the juice—after liming and sulphi
tation—by automatic pH control systems. Instrumentation and control systems
are available for controlling both lime addition and S 0 2 .
The milk of lime is prepared by slaking C a O (burnt lime) with water in a lime
slaker. The grit is removed and thrown out and the lime water—called the milk of
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27 Processing of sugarcane into white sugar
lime is stored in a tank after passing it through a classifier. The milk of lime is stirred continuously. The concentration is maintained constant at about 15° brix.
The sulphur dioxide gas is continuously produced in specially made sulphur burners. The sulphur burner consists of a melter in which the sulphur is preloaded and kept in molten condition. The molten sulphur is fed into the burner, either continuously or batch by batch. Compressed air is blown into the burner. The sulphur is converted into sulphur dioxide gas which is carried through a scrubber and bubbled through the limed juice in the juice treatment tank. T h e temperature of S 0 2 gas is controlled at the burner itself and subsequently it is also cooled by passing it through water jacketed pipes to avoid sublimation and formation of sulphur trioxide. The sulphur dioxide becomes sulphurous acid wi th moisture in the juice and the sulphurous acid forms calcium sulphite, after reacting with calcium hydroxide in the juice liming-sulphitation tank. The calcium sulphite precipitate settles down easily in the clarifier.
The treated juice after treatment with milk of lime and sulphur dioxide gas, is heated again up to 100 °C+, and sent to specially designed clarifiers where a retention period of about 2V2 h is allowed. In the clarifier, the precipitates that are formed during liming, sulphitation and heating are allowed to settle down a n d the sediment is collected at the bottom of each tray of the multi-tray clarifier. T h e clarifier is designed to work continuously with proper arrangements for entry of juice at the centre and multiple withdrawal at the periphery. Short circuiting a n d formation of dead packets are kept at a minimum.
Cane juice contains a certain amount of phosphate in it. It is generally in t h e order of 200 to 300 ppm. The phosphate in the form of phosphoric acid reacts with calcium hydroxide to form a heavy calcium phosphate precipitate. The calcium phosphate absorbs colloidal particles and forms thick floes and facilitates quick sedimentation in the clarifier and improves the clarity of the decanted clear juice. If the phosphate in the mixed juice is found to be wanting (less than 3 0 0 ppm), it is generally made up by the addition of phosphoric acid into the mixed juice in a measured dose.
Besides, certain high molecular weight polymeric compounds are also used as settling aids. A number of polymeric chemicals with brand names are available in the market. Some of them are more effective in acidic medium and some of t h e m in alkaline medium. But most of them are moderately effective around neutral pH. The settling aids are generally used in small doses, in the order of 1 to 2 p p m . In the case of refractory juices slightly higher doses are added.
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The clarifier consists of a flocculating chamber and generally four chambers. The juice enters into each chamber and is withdrawn from each chamber. The sediments settled down at the bottom cone of each chamber are also withdrawn severally. The outside surface of the clarifier is well insulated to avoid loss of temperature of juice inside the clarifier.
Specially designed single tray clarifiers are also working with good results. The retention time in such clarifiers is claimed to be about one hour. However their use in white sugar manufacture is uncommon.
27.2.3 Fi l trat ion of sediments
The sediment settled in each compartment is generally called 'mud' or muddy
juice. The muddy juice is withdrawn on a continuous basis, (some prefer to draw
it in batches) and filtered through rotary vacuum filters. Before taking it to the
filter, it is mixed with the fine powder of bagasse called bagacillro which acts as a
filter medium. Bagacillro is collected by screening the bagasse while the bagasse is
moving to the boiler station from the mill, and blown through a blower into a
mixer where it is mixed with the muddy juice. The muddy juice from the mixer is
allowed to flow into the trough of the filter.
The drum filter is installed above the trough, with the bottom position of the
drum being immersed in the muddy juice in the trough. As the vacuum filter
drum rotates, the filtrate is sucked through a network of pipelines and the mud
adheres as a thick layer on the screen of the drum. The layer is washed with a spray
of water to reduce the traces of sugar in the mud and the washed liquor is also
recycled back for processing. The mud layer is scraped continuously and removed.
This mud is generally used as a fertiliser after composting for about 60 to 90 days.
Recently, technologies have been developed to convert the mud into a
biofertiliser—a value-added product along with the distillery effluents. Attempts
are also being made to produce biogas out of filter mud.
27.3
EVAPORATION OF WATER
The clear decanted juice from the clarifier which is generally called as clarified
juice would be having about 13 to 15% solids; the balance is water. The entire
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water is to be evaporated before the sugar is crystallised out. The evaporation is done in two stages. In the first stage, the evaporation is carried out until the so l id content is about 60 to 65%. In the second stage, further evaporation is carried o u t in a controlled manner when crystallisation takes place.
The first stage of evaporation is done in a multiple-effect evaporator sys tem. The multiple evaporator system offers two great advantages. It results in g r ea t steam economy. The steam economy increases with the increase in the effects in the system. In a triple effect, the steam consumption is roughly one third and in a quadruple effect it is one fourth and so on, when compared to the steam c o n sumption in a single effect evaporator.
Another advantage of using multiple effect for evaporation is that the sys tem allows boiling of the juice in partial vacuum and hence at a lower t empera tu re . The boiling temperatures are lower in successive effects, the lowest being in t h e last effect where the concentration of the juice is the highest. The sugar so lu t i on cannot withstand high temperatures, particularly at higher concentrations.
The last effect is connected to a condenser where the vapours are drawn a n d condensed. The continuous condensation of vapour by spraying cold water creates a vacuum inside the last effect to the extent of about 650 mm (mercury) w i th t h e corresponding boiling temperature of about 55 °C. Depending upon the drawal of vapour and its condensation in the calandrias, the partial pressure (vacuum) is maintained in other effects with corresponding temperatures. The total pressure difference and hence the temperature difference (which is the driving force), be tween the calandria of the first effect and the vapour space of the last effect gets d i s t r ibu ted between the effects depending upon the vapour withdrawal. In a straight evapora tor set, the steam consumed is equal to roughly the total quantity of water evapora ted divided by the number of effects in the set. This also means that the evaporation is roughly equal in all the effects. With the given heating surface and the heat t ransfer coefficient in each effect, the temperature difference (At) between the effects gets adjusted to keep the evaporation equal in all the effects.
3.1 Vapour bleeding
To further economise on the total steam consumption, extensive vapour b l e e d i n g is resorted to, which means withdrawal of vapours from different effects of e v a p o rators for the purpose of juice heating and pan boiling. Instead of using e x h a u s t steam in juice heaters and pan boiling, vapours from the effects III, II a n d I of t h e
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Sugarcane in agriculture and industry
evaporator set, are used. In modern sugar mills the entire pan boiling is done
using vapour from the effect II. The raw juice heating is done out of vapour from
the effect III and the treated juice heating is done by the vapours of effects II and
I in two stages. This is possible in the case of quadruple and quintuple effect
evaporators. With extensive vapour bleeding as above, while there is still substan
tial economy by going to quadruple effect from triple effect, there is no substan
tial benefit by going to quintuple from quadruple effect. The quintuple effect
increases the initial investment and also the maintenance cost.
The vapour bleeding reduces the vapour going out to the condenser. Higher
the vapour bleeding, lower is the vapour going to condenser. The objective should
be to reach a point where the vapour going to evaporator condenser is close to nil.
This can be very nearly achieved by installing an online juice heater in the path of
the vapour between the last body and the condenser. It can be generally stated that
the steam consumption in the evaporator is equivalent to the total vapours bled
plus the vapour going to the condenser. If the vapour bleeding is achieved to reach
"nearly nil vapour to condenser" stage in the evaporator, the total process steam
consumption is just equal to the steam consumption at juice heaters and pans.
Effectively, the steam consumption for evaporation can be deemed as nil.
It is theoretically possible to achieve "absolute nil vapour to condenser" by
using the cold jaw juice itself to condense the vapours in the evaporator con
denser (by direct contact). The total heat in the vapour is recovered for heating
the cold raw juice.
With the above, the total steam consumption in a white sugar factory can be
brought down close to 40% on the cane and in a raw sugar factory close to 35%
on the cane. The condensates from the calandria of the juice heaters and evapora
tor vessels must be extracted on a continuous basis. The accumulation of conden
sates often will result in water hammering besides reducing the effective heating
surface and thereby affecting the evaporation rate.
Appropriate heights with closed system should be provided for the gravity flow
of condensates and to provide a positive head to the pump. The condensates are
recycled back in the process for various purposes. The entire condensates of the
steam are pumped back into the boiler feed water tank. The vapour condensates
are used for imbibition, pan floor requirements and also for centrifugal require
ments. A small quantity of condensates from the first vapour is also used as 'make
up' for boiler feed water. The condensate that is used for boiler make up should be
416
free from traces of sugar. Often condensates are cooled to some degree before
using for imbibition. Condensate is soft water and hence is ideal for use as
imbibition water.
To get the full benefit of the evaporator set, the approach should be to have
maximum pressure difference (AP) or maximum temperature difference (AT) be
tween the exhaust steam in the calandria of the first effect and the vapour space of
the last effect. There is a limit for achieving the vacuum in the last effect which is
decided by the atmospheric pressure and the temperature of the cold water avail
able. While so, the exhaust steam pressure can be increased which again has limi
tations due to the fact that the inversion of sugar in the juice takes place at higher
temperatures. The inversion is a function of temperature, concentration, and time.
With more and more vapour bleeding, the juice reaches higher concentrations
even in earlier effects where the temperatures are comparatively higher. Hence
two of the three factors are unfavourable when the exhaust steam pressure in
creases which becomes necessary for extensive vapour bleeding. To compensate
for both these factors, the third factor, namely, the time has to be reduced. It is
possible to reduce the retention time in the evaporator vessels, particularly in
those vessels where the temperatures are high.
Falling film vessels are found to be successful in reducing the retention time
especially in the first and second effects. In the falling vessels, the juice flows from
the top towards the bottom of the vessels along the walls of the tubes as a thin
film. As it reaches the bottom well, it is pumped out. Falling film evaporators also
offer another great advantage in that there is no loss of temperature difference due
to hydraulic head which happens in normal evaporators where there is always a
certain level of juice maintained in the body which has to rise through the tube to
the top of the calandria. There is a temperature difference between the bottom of
the juice column and the vapours generated at the top of the juice level. This is an
effective loss in temperature difference. Hence the falling film permits lesser tem
perature difference for giving the same rate of evaporation. In other words, for a
given heating surface and given gross temperature difference, the evaporation in a
falling film evaporator is higher.
The falling film evaporator offers one more advantage—being a long tube evapo
rator the number of tubes for a given heating surface is less and hence the distri
bution of juice becomes easy. This is true particularly for large vessels. In case of a
rising film with long tubes, the retention period further increases and the loss of
temperature difference is also higher.
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27 Processing of sugarcane into white sugar
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27 Processing of sugarcane into white sugar
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27 Processing of sugarcane into white sugar
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27 Processing of sugarcane into white sugar
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It is also observed in practice that in falling film evaporator bodies, the scaling is considerably less.
The disadvantage in the falling film evaporator is the requirement of pumps for recirculation and transferring to the next body; hence additional power is consumed.
Some of the choices in the evaporator configuration are given below. A balance has to be struck between the steam, economy, initial investment, maintenance problems and cost.
Assumption
Cane crushed
Clear juice
Brix of clear juice
Brixy syrup Evaporation
Water evaporated
Steam consumption
a) for raw juice
b) for treated juice
c) for pan boiling
d) water added for desuperheating
e) steam for clear juice heating
100 t/h
100 t/h
13.00
65.00 80%
80 t/h
7.0% cane
7.0% cane
22.0% cane
4.0% cane
4.0% cane
27.3.2 Comments
In straight evaporator sets, the advantages are highly significant when the number
of effects are increased from 3 to 4 and from 4 to 5. But with extensive vapour
bleeding, the advantage is significant only when 3 effects are increased to 4 effects
and not when 4 effects are increased to 5 effects. Similarly the vapour line juice
heater saves steam considerably in case of triple effects whereas it is not found that
advantageous in case of quadruple and quintuple sets.
Considering the total heating surface and also the operational and mainte
nance problems including cleaning of heating surfaces, it is advisable to limit the
number of effects to four and also avoid the vapour line juice heater. Alternatively
in a quintuple set the raw juice heating can be done in two stages. One from the
fourth vapour and the second from the third vapour. This will bring down the
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27 Processing of sugarcane into white sugar
steam consumption in the evaporator to 36.2 ton which is also not very significant compared to the additional power required to pump through double juice heaters and the operational problems.
The choice is ultimately made by calculating the saved incremental steam in terms of power generation in the condensing steam turbine.
In any case, the total steam consumption cannot be reduced below 41% cane which is equivalent to the steam consumption for juice heating, pan boiling and other purposes. Of course, there is a scope for reducing the steam consumption in pan boiling from 22% to about 20% by using continuous pans and with instrumentation. Theoretically the steam required for pan boiling for white sugar manufacture is even less.
The above calculations are approximate but good enough for comparison purposes. If detailed calculations are made considering the total heat of exhaust steam, all vapours, etc. the evaporation and steam consumption figures vary slightly. All calculations are on the basis that one kg of steam/vapour evaporates one kg of water. Similarly the steam consumption at juice heaters and vacuum pans varies with juice per cent cane and the boiling scheme and also the curing schemes.
The above calculations will help one decide on the evaporator configuration.
27.3.3 Extract ion of non-condensables
While the juice is boiling in evaporators, certain gases are generated which are not condensable and get accumulated in the calandria. These gases develop pressure inside the calandria if not removed and obstruct the free entry of vapours, affecting the evaporation in the previous effect. The evaporation, if reduced in one effect for any reason reduces the evaporation in all the effects correspondingly. The non-condensable gases from each calandria are regularly and continuously removed and vented by connecting it to a lower pressure (higher vacuum) zone through suitably sized pipelines with control valves. This is applicable for the calandria of juice heaters and vacuum pans too. If there is a positive pressure in the calandria, the vents can be opened out to atmosphere. Otherwise the venting can be done to the vapour pipe of lower pressure. Proper venting of the non-condensable gases and avoiding leakage of air into the vacuum system in the evaporator and also the connected calandria of the juice heaters are very important for the proper working of the vapour bleeding arrangement.
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27.3.4 Condensate ext ract ion
Once the steam or vapour gives away its latent heat it gets condensed. Hence the
condensation of steam is continuous in all the calandria—the evaporators, juice
heaters, and pans. The condensates in the respective calandria must be removed
continuously to make way for the fresh steam/vapour to enter the calandria. As
different calandria are under different pressures, the condensate extraction system
should be properly designed to allow adequate positive head for the respective
condensates to flow freely to the pump suction to facilitate continuous pumping.
The whole system should be leak-proof.
27.3.5 Flashing of condensates
When the condensates from higher pressure calandria are exposed to lower pres
sure calandria, the condensates flash and the vapours so generated can be utilized
in the calandria of lower pressures. By a proper network of pipelines, all vapours
can be flashed with benefit.
27.3.6 Syrup sulphi tat ion
In white sugar manufacture it is necessary to bleach the syrup coming out of the
evaporators. For this purpose sulphur dioxide gas is used. The S 0 2 gas is gener
ated in the sulphur burner (as explained earlier) and the gas is bubbled through
the column of syrup in the syrup sulphitation tank. The pH of the syrup which is
generally in the range 6.0—6.2 is brought down to about 5.0-5.10. Excess of sul
phitation to a pH below 5.0 is found to cause inversion. It is also found to release
more free S 0 2 gas in the pan boiling affecting the vapour pipes, condensers, and
also bringing down the pH of injection water. If the sulphitation is inadequate the
final sugar quality in terms of colour will not be good.
27 .4
CRYSTALLIZATION IN VACUUM PANS (PAN BOILING)
The evaporation of water is done in two stages, the first being in multiple effect
evaporators. The second stage of evaporation involves crystallisation of sugar in
terms of crystal formation and crystal growth. Until syrup sulphitation (from the
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27 Processing of sugarcane into white sugar
milling) the process is continuous. Once the syrup comes to the pan floor it is stored in storage tanks and further processing becomes batchwise. Even with continuous pans, the pan boiling process is not totally continuous as certain operations like 'graining' and 'footing' are done batch by batch. The evaporation rate varies from stage to stage. Besides, in the pan floor there are a number of materials stored in storage tanks, other than syrup also, such as melt and molasses like—A light, A-Heavy, B-Heavy, C-Light, etc. Often more than one material is used in the same pan for boiling in different sequences and hence a continuous flow of syrup at this stage is impracticable.
Generally the crystallisation is done in three stages, which means the sugar from the syrup is recovered by three crops by three successive crystallisations. "When the crystals are formed and grown in the media of syrup, the syrup gets exhausted of sugar while the sugar crystals grow in size and the mixture finally reaches an equilibrium stage between the exhausted mother liquor, which is called molasses and the crystal content and its total surface area. This stage depends upon the purity of the initial mother liquor and the total crystal surface area. Once this equilibrium is reached the boiling is stopped and the product in the vacuum pan, which is called A-massecuite, is dropped into the crystalliser, which is at atmospheric pressure. The massecuite contains sugar crystals and molasses. The molasses after separation from crystals in the centrifugals will be still rich in sugar. This molasses, called A-heavy molasses is boiled again and a second crop of sugar is recovered by crystallisation. Similarly the A-heavy molasses gets exhausted of sugar and reaches an equilibrium. The purity of the mother liquor after reaching equilibrium in this case is much lower when compared to that in the first boiling (A-massecuite). The product that becomes ready in the second boiling is called B-massecuite. The B-massecuite is again centrifuged and the molasses called B-heavy molasses is separated out which is again boiled and the third crop of sugar is crystallised out. The product of the third boiling is called C-massecuite. Generally only three boiling schemes are followed; this is found adequate and economical to exhaust the molasses to minimum sugar content and extract maximum sugar.
In normal practice, actual crystallisation is done only in the last massecuite. The graining (formation of initial crystals and stabilising them) is done on a fairly higher purity medium like A-heavy molasses or sometimes a mixture of syrup and A-heavy molasses (depending upon the purities) and the grains are developed by
429
boiling with B-heavy molasses. This boiling is done carefully in a controlled way
so that the evaporation matches that of the movement and deposition of sugar
molecules on the surface of the existing crystals. Either continuous or in batches,
feed of the molasses is given to match the evaporation rate. During the process the
crystals grow and the molasses gets exhausted of sugar. When the crystal size is
found optimum, by which time, the capacity of vessel is also fully utilised, the
massecuite is concentrated to the maximum extent, the boiling is stopped and it is
dropped into the crystalliser. The final massecuite (C-massecuite) is very thick
with about 100 ° brix and is dark coloured. The mother liquor (C-molasses or
final molasses) is highly viscous. Hence it is difficult to separate the crystals effec
tively from molasses in the centrifugals without the use of some wash water. But
use of wash water results in the sugar dissolving in the centrifugals finding its way
into the molasses which is sent out. To overcome this problem the final massecuite
is centrifuged twice. First, the concentrated final molasses is centrifuged out to
the maximum possible extent without resorting to washing so that the molasses
which is sent out contains minimum sugar. The crystals that are separated will be
brown in colour and magmised, and are centrifuged using water to remove the
adhering molasses. The sugar coming out which is called C-double cured sugar or
C-seed is fairly white in colour and of purity above 95, though smaller in size. The
molasses from this is recycled in the process.
Similarly when the B-massecuite is cured the sugar that comes out of the cen
trifugal will be of 97—98 purity but not good enough for packing. This sugar is
magmised and called B-seed. Only A-sugar is taken for packing and marketing.
The normal practice in a three boiling system is to use C-seed as the starting
material for B-massecuite and the B-seed as the starting material for A-massecuite.
Thus the sugar moves upwards from C to A, while getting improved in size and
purity, whereas the molasses move downwards from A to C, while getting ex
hausted of sugar at each stage. There are practices slighdy differing from the above,
but basically the three boiling scheme is generally practised.
The objective of the boiling scheme is to get best quality sugar, losing least sugar
in the final molasses and also with minimum re-circulation or recycling of materials
in the process. More circulation means more sugar loss and higher steam
consumption. The clarification process being the same, better sugar means more re
circulation and more steam consumption. A compromise then becomes necessary.
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27 Processing of sugarcane into white sugar
The first massecuite (A-massecuite) is production massecuite and hence the objective is to get good quality sugar in the sense that the crystal size should be uniform (the crystal size depending upon the market choice). The colour should match the standards. In India where maximum direct consumption white sugar is manufactured, the colour of the sugar is judged by matching it physically with the standard sugar. The international standard (ICUMSA) still maintains the colour comparison in liquid phase only, though ICUMSA is not really meant for direct consumption white sugar. India also started using ICUMSA standards for comparison, particularly for export purposes. An ICUMSA figure of less than 100 for white sugar is supposed to be good, when produced with double sulphitation process. However factories have improved the colour to as good as 40 ICUMSA standard by adopting the syrup purification process.
The C-massecuite is called recovery massecuite. The objective of this massecuite is to recover maximum sugar by exhausting the molasses as much as feasible. The sugar from this massecuite is obviously melted and recycled in process.
The B-massecuite is an intermediate strike which serves both the purposes. It helps in improving the purity of A-massecuite and thereby the quality of the product, at the same time aiding to reduce the purity of C-massecuite and thereby reducing the purity of the final molasses. Hence the B-massecuite purity is to be manipulated in such a way as to get a good compromise between the two objectives.
It is possible to maintain the purities of A-massecuite and C-massecuite as constant at the desired levels by manipulating the B-massecuite purity irrespective of the virgin syrup purity. Depending upon the syrup purity the B-massecuite purity can be so adjusted that the A-massecuite purity remains the same always and also at a level as high as possible so that the quality of the final product is uniform and good. At the same time the B-massecuite should produce the BH molasses with purity adequately low to keep the C-massecuite purity under control.
Vacuum: The lower the temperature of boiling in the pan, the better will be the quality of sugar and also lower would be the steam consumption. Hence it is always advantageous to keep the boiling temperature as low as possible, which means the vacuum inside the pan must be maintained as high as possible and must be constant also. Fluctuations in vacuum will vary the boiling temperatures suddenly affecting the boiling. For maintaining the vacuum, the condensing of the vapour as well as removal of non-condensables, must be efficient in the condenser.
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A satisfactory performance of the condenser is achieved by spraying cold water at a temperature as close to the wet bulb temperature as possible, having an efficient spray of cold water and also by efficient removal of non-condensables. Leakage of air into the system should be totally avoided as it reduces the vacuum in the system. In a good condenser the approach temperature (rise in temperature of cold water by absorbing heat from the vapour) is 7-8 °C. But normally it is about 5 to 6 °C. Of course, it also depends upon the initial cold water temperature.
In addition to the efficient cooling of vapours, efficient ejection of the noncondensables and leaked air is also very important. The water required to eject them through a set of jet nipples is more than that required for cooling.
27.4.1 Cool ing of condenser wa te r ( inject ion water)
The quantity of cold water which is used for cooling and ejecting in the condenser is quite large—of the order of 80 to 100 times the quantity of vapour condensed or roughly 1 ton of water per ton of cane crushed. Obviously so much water cannot be pumped into the system as fresh water, nor can it be let out as effluent. Hence the entire quantity is recycled after cooling.
Generally the cooling is achieved by spraying the water in the atmosphere under pressure allowing for adiabatic expansion. Alternatively cooling towers are also used to cool water.
While the vapours condensed increase the water going out of the condenser, the hot water when cooled in the spray pond gets reduced because of the evaporation. Thus the quantity of water remains constant. However some make-up water is used continuously allowing an equal quantity of water to exit from the system.
27 .5
CRYSTALLISERS
In the vacuum pan, the boiling takes place until an equilibrium is reached between the crystal content and the mother liquor purity. When the crystal size has reached the desired size, the massecuite is discharged from the pan into another vessel called crystalliser. The crystallisers are provided with a cooling system for cooling the massecuite. The massecuite is allowed time in the crystailiser. The crystallisers are equipped with cooling coils in which cold water is circulated.
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27 Processing of sugarcane into white sugar
During the cooling further crystallisation takes place and the molasses gets further exhausted of sugar. Practically no energy is spent for crystallisation in the crystallisers.
Generally the cooling arrangements are made in crystallisers for all types of massecuite with the difference that the A- and B-massecuites are cooled down to about 50 °C to 55 °C and C-massecuite to about 40 °C.
27.5.1 Reheating
While A-& B-massecuites which are cooled to about 50 to 55 °C can be cured in centrifugals effectively, the C-massecuite which is cooled to 40 °C cannot be cured. Hence it is necessary to reheat the C-massecuite to about 50 to 55 °C before centrifuging. Reheating is done without undoing the crystallisation that took place during cooling. The fact that the sugar solution can reach super saturation helps in achieving this. Further, a special type of heater called transient heater heats the cooled massecuite very quickly and the massecuite is cured before any crystal dissolution starts.
Even in the crystallisers the rate of cooling is to be controlled in such a way that the sugar molecules which crystallise out should find a place to deposit on the crystals. Too rapid cooling may result in dust formation which will find its way out through the molasses in the centrifugals. Too slow cooling may result in inadequate exhaustion. Generally cooling times (with water cooled coils) of 6 hours for A- and B-massecuites and about 16 hours for C-massecuite are found optimum. About 2 °C per hour in case of B-and C-massecuites and about 1.5 °C per hour in case of C-massecuite would give good results.
27 .6
CENTRIFUGING
The massecuite after cooling is centrifuged in centrifugals to separate the mother liquor (molasses) from the crystals. There are two types of centrifugals used for the purpose. Batch type centrifugals are used to cure A-massecuite and continuous centrifugals are used for curing B-& C-massecuites. Often part of the B-massecuite is cured in batch type centrifugals to use the cured sugar as die seed for footing for A-massecuite. The sugar coming out of the continuous centrifugal is
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Sugarcane in agriculture and industry
generally melted and the melt liquor is used for boiling in A-massecuite. The C-massecuite is very thick and viscous. Hence centrifuging this massecuite offers resistance. To reduce the viscosity and ease curing, the massecuite is reheated immediately before it enters the centrifugal. In addition, a little water or dilute final molasses (the latter is preferred) is used at the entry of the massecuite to the centrifugal. While these steps help in improving the curing, it would not allow dissolving of the crystals. In spite of all these, the sugar coming out of the first centrifuging would be brown in colour, having a purity of 80 to 85 only. Further efforts to increase the purity of the cured sugar will result in and increase in the final molasses purity. Hence the curing of C-massecuite is divided into two parts. The first part is to separate the concentrated molasses with minimum sugar content. In the second part the first cured sugar is cured again by magmising it with water or AH molasses, etc. The second cured sugar will be of about 94-95 purity which is melted and re-crystallised in A-massecuite. The molasses coming out in the second curing is called C-light molasses which is used in C- massecuite. While the re-circulation is not reduced by second curing, the materials are segregated and sent out through the nearest route. For example the 80/85 purity of first cured sugar is segregated into two parts, namely, C-double cured sugar of 95 purity and CL molasses of about 60 purity. The 95-purity material goes to A-massecuite and most of it finds its way into the final product. The 65-purity material (low purity) goes to C-massecuite and the non-sugar of this material finds its way into the final molasses.
A-curing in the earlier days was done in two stages; today it is common to cure in a single stage, washing with only superheated water instead of steam and water. The modern high speed and high gravity factor centrifugals perform very efficiently making double curing redundant. Single curing is giving excellent results in terms of sugar quality. Double curing results in enormous re-circulation of sugar beside increasing the power consumption, initial investment, maintenance cost, etc.
In the modern centrifugals, the drives with stepped speed multi-pole motor have been replaced by thyristor controlled AC drives with step-less speed variations. These centrifugals with flat bottoms are fully automatic and can recycle as high as 16 cycles/hour. These machines are not only energy efficient, but also highly productive as there is no time loss during the change of speeds, both upwards and downwards.
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27 Processing of sugarcane into white sugar
27.6.1 Superheated water wash
Superheated water wash replaces steam wash and hot water wash. It reduces the total cycle time and increases the productivity of the machine. Besides superheated water washing facilitates quick drying of sugar on the hopper. Thus it improves the quality of sugar and reduces re-circulation and increases the machine capacity. The temperature of the super heated water is maintained generally at 120/125 °C. The temperature is controlled automatically by proper instrumentation. The duration of wash depends upon the size of crystals and massecuite.
27.6.2 Molasses separation
The mother liquor separated in the centrifugal will be thick and of lower purity until the water wash is opened in the centrifugals. Subsequent to water opening, due to dissolution of sugar the molasses purity increases. For the most effective recycling of the molasses into the processes, it is prudent to separate the molasses into two streams, one being heavy molasses without dilution and the other being the light molasses which comes out after washing starts. The cut-off point for separation can be fixed and made to operate automatically based on timers. The higher purity molasses (light) goes back to higher grade massecuite A-massecuite and the lower purity molasses (heavy) goes to B-massecuite and C-massecuite.
27.6.3 Magmising
The C-fore worker is generally magmised with C-light molasses. Some factories use AH molasses. Some other factories who keep the C-fore worker sugar purity low to avoid the purity of the final molasses going up, use water for magmising.
27.7
SUGAR DRYING, GRADING, PACKING AND STORING
27.7.1 Sugar dry ing
In most places in case of white sugar manufacturing, hopper drying is practised. The sugar is made to hop on multi-deck hopper conveyors while the hot air,
435
Sugarcane in agriculture and industry
followed by cold air is blown, which will dry and cool the sugar. The lumps are
separated out.
27.7.1 Sugar grading
Grader: The sugar is carried through elevators from the hopper and made to
fall on a multi-deck vibrating grader consisting of 3 or 4 screens arranged one
above the other. Some lumps, joint crystals, etc. are separated out on the top
screen whereas the dust is passed through the lowest screen and taken back into
the process. T h e middle decks are fitted with suitable screens to separate and
collect the sugar in two or three grades sizewise.
The sugar collected from the graders are separately stored gradewise in bins
from where it is filled in bags, weighed automatically, and packed.
27.7.3 Warehouse
The sugar industry is a seasonal industry and hence the production takes place only in some part of the year whereas the consumption of sugar takes place all through the year. So in case of white sugar manufacturing, the production cannot be shipped out as and when produced. A substantial quantity of sugar is to be stored in properly constructed warehouses. Sugar being hygroscopic, the construction of the warehouse needs special attention. The flooring has to be water proof. The roof also has to be protected. In areas of heavy rains, even the roof is covered with a thin layer of waterproof material on the roof sheets. Care should be taken to see that the humidity inside the godown is not too high or not too low. The ventilation is to be controlled accordingly.
Generally sugar is bagged in 100 kg bags in India. Elsewhere it is bagged in 50 kg bags.
436
Glossary
Some technical terms used in a sugar factory. 1. Bagasse—the residue of cane after crushing in one mill or a train of mills. 2. Brix is the percentage of total solids dissolved in a liquid or in a sugar solution. 3. CCS—Commercial Cane Sugar estimated by any of the empirical formulae. 4. DRIS—Diagnosis and Recommendation Integrated System—a method of
leaf analysis where nutrient ratios are used. 5. Fibre—the dry, water insoluble matter in cane. 6. Filter cake—the material retained on the screens or cloth of the filters. 7. First expressed juice—the juice expressed by the first two rollers of a mill
tandem. 8. Java Ratio (JR)
JR = Sucrose or (pol) % cane /Sucrose (pol)% first expressed juice. 9. Magma—a mechanical mixture of crystals and molasses or heavy syrup. 10. Massecuite—the concentrated syrup or molasses in which the sugar has
been crystallized. 11. Molasses—when massecuite is spun in a centrifugal machine the sugar crys
tals are separated from the mother liquor termed molasses. 12. Planooning—a plant crop and a single ratoon. 13. Purity or purity coefficient—purity is the cane sugar present in percentage
terms of the solid matter. Purity % = Sucrose or pol/corrected brix x 100 The corrected brix is for temperature correction.
14. Recovery per cent—total tons sugar bagged per 100 tons of cane crushed. 15. Reducing Sugars (RS)—reducing sugars in cane its products interpreted as
invert sugar. Invert sugars are made up of glucose and fructose 16. RS ratio or invert ratio or invert.
RS ratio (invert) = % Reducing sugars x 100 /% sucrose 17. Sucrose or pol—pol is the value determined by direct or single polarization
of a normal weight solution in a saccharimeter. 18. The final molasses is the liquid residue from which no more sugar can be
removed economically. This is also called 'black strap' in the trade. 19. Vinasse or dunder—the liquid distillery effluent is the extracted residue
remaining after alcohol has been separated by distillation. 20. Virgin cane—usually plant cane.
437
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POLLUTION PROBLEMS AND CONTROL MEASURES
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25
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457
Appendixes
Appendix 1 Estimated targets of sugarcane production and area requirement
Source: Task force on sugar industry for the 9th five year plan issued by Directorate of Sugar.
Appendix 2 Estimated per capita consumption during the 9th plan
Source: Task force on sugar industry for the 9th five year plan issued by Directorate of Sugar.
Appendix 3 MS Medium
Appendixes
Source: Kyte and Keyn, 1996.
459
SUGARCANE GROWING REGIONS OF INDIA
461
A
A-massecuice 429 A. flavus 216
abiotic stresses 283
abscisic acid 304
Acacia 398
Acacia albida 111
Acaulospora 158
acesulfame-K 2, 325
Acetobacter 138, 144, 145
Acetobacter diazotrophicus 140, 141,
186, 187
acetogenesis 369
acid sulphate soils 51
acid-invertase 300, 301
Aconitic acid 354
Activated carbon 346
Activated sludge 366
additive series 112
adjuvant(s) 263, 267
Adsali 78
Adventitious roots 99
Aerated Steam Therapy (AST) 252
Aerenchyma 99
aerobic system 363
Agallol 76
agglomerated products 340
agro-climatic zones 9
Agrobacterium 147, 257, 289
Agrobacterium radiobacter 155, 156, 188
Agronomic efficiency 127, 128
Albizia falcataria 111
Albizzia 147
Alditol 325
alfacellulose 345, 346
Align method of planting 85
allelochemicals 241, 344
Allelopathy 240,241
Allophanes 169
Alternate furrow irrigation 101
alternatively alternate furrow
irrigation 101
AM hyphae 158
amylase 303
anaerobic digestion 369
anaerobic lagooning 370
anaerobic system 363
animal chocolates 356
antidotes 264, 267
apparently healthy 285
Aqua petrohol 352
Arbuscular mycorrhizae 158
Arceneaux's universal equation 308
Areton 76, 283
arrow 24
Artificial sweeteners 2
Aspartame 2, 325
Aspergillus 147
Aspergillus awamori 156, 187, 188, 216
Aspergillus flavipus 345
Aspergillus niger 216, 354
associative N2 fixers
(Rhizocoenosis) 186
ATPase 303
auriculiformis 111
Australian CCS formula 310
Index
Sugarcane in agriculture and industry
Autotoxicity 240
Autumn planting 78,109
Available Soil Moisture (ASM) 189, 234
Azadirachta indica 212
Azospirllum 138, 140, 141, 144, 145,
186,213,214,237,242
AzospiriUum brasilense 345
Azotobacter 138, 140, 141, 144, 145, 147, 186,213,237,242
B
B 37172 47
Bacillus 138, 140, 147, 186, 216
Bacillus megatherium 155, 156,
188, 216
Bacillus polymyxa 157, 187
back crossing 20
back-firing 316
bacterial wilt 115
bactericides 336
Bactrinol 313
Badila 18
bagacillo 359, 362
bagasse 333
Bagasse briquettes 341
bagasse logs 341
bagasse mat 402
bar gene 257
Bavistin 283,284
Bayleton 253
Benlate 281
benornyl 283,284
Bhal 53
Bhargava Commission 373, 374
Bhargava formulae 374, 376
bhat and bangar 53
Bhendi 320
Bhumi Labh 360
Bi-wall system 201
billets 314
binding material 378
biocide 355
bioearth 359, 371
Biofilters 365
Biofiltration 366
Biofuels 352
biogas 360
biogas (methane) 360
Bioherbicides 257
bioliquor 338
Biological methods 256, 368
Biological Nitrogen Fixation (BNF) 140
Biological Oxygen Demand (BOD) 6,
350, 362, 363, 367, 368, 370, 371
Biological Software (BSW) 186
Biological suppression of weeds 256
biomass 333, 349, 350, 351, 352, 367
biomass cost 350
Biostil process 350, 352
Biotic stresses 283
Black Strap Molasses 352
Bagasse Newsprint (BNP) 338, 340
break crop 106
brown sugar 323
bud chips 88
bud groove 23
Bulk Density (BD) 55, 208
Bulk planting 311
bullock carts 313
bullock-drawn ridgers 95
462
Index
bunchy top 269
Bura 323
Burnt cane 307
buttress roots 24
by-product 375
C
calandria 427
calcium phosphate 411
Callus culture 389
Cane fires 316
cane preparation 406
Cane registration 311
Cane Tops and Leaves (CTL) 344
CaO (burnt lime) 412
Carbendazim 252, 281
cascade fermentation 352
Casuarina 398
Casuarina equistifolia 111
catalysts 303
catch crops 106
cattle licks 356
cellulolysis 187
Cellulomonas 187
Central pollution boards 362
certified seed 252
Chemical Oxygen Demand
(COD) 362,367
chemigation 202
chemotherapy 281
Chip-bud cutting machine 88
chlorophyll 133
Citric acid 354
Cladosporium 345
closely spaced 77
Clostridium 352
C 0 2 concentration 67
Cogeneration of power 360, 375, 378
collateral hosts 254
combine harvester 314
commercial crop 330
commercial seed 252
comprehensive models 293
Conservation tillage 53
Contact herbicides 257
Contour system 87
copper oxychloride 284
cream jaggery 321, 346
critical period 195
crop coefficient Kc 235
Crop log 224
crop logging 180
crop residues 147
crop rotation 281
Cryopreservation 393
crystallisation 433
crystallisers 433
crystals 435
Cumulative Pan Evaporation
(CPE) 195,234
Curve sickle 312
cut-out 190, 311
cut-out period 304, 306
Cytozyme 240
D
dead hearts 269, 270, 271 Deep trench planting 83 dehydrogenases 367 delignification 537
463
Sugarcane in agriculture and industry
depithing 336
Detrashing 270, 274
Dhiancha 147
Diagnosis and Recommendation Integrated System (DRIS) 181, 224, 225, 226
diazotrophy 187
difficult-to-ripen 60
difficult-to-ripen areas 303
disc ploughing 73
diurnal variations 70
Doab 53
Doneilly Chutes 403
DRIS index 225
DRIS model 181
dry matter 6
dry off 190,306,311
dry planting 95
drying off 304
dunder 367
E
early maturing 43
earthing up 95, 265
earthworms 147, 188
eelworms 286
effluent 367
Effluent Treatment Plant (ETP) 364,
365
Eksali 78
Electro Ultra Filtration (EUF) 162
electroporation 290
elephant grass 273
Embryo culture 397
embryogenesis 389
Eminan 6, 76
empirical models 293, 295 energy cane 346
enhancer 304 Enterobacter 138, 140
entomopathogens 278
entomophages 278
environmental contribution 288
Enzyme Commission 301
Erianthus 16
Essential Commodity Act 375
esterase activity 304
Estimated Recoverable Sugar 309
ET 235, 236
ET and EO 191
ET or CU 191
Ethephon 304, 306
ethrel (Ethephon) 50
ex vitro 391
Exchangeable Sodium Percentage
(ESP) 103
explant 389
exponential 126
External P Requirement 151
extraneous matter 313
extravitrum 391
F
Fairs bands 98
Falling film 417
FAO model 58, 59
farming system 119
feeder root system 220
fertigation 202
fibre 334
464
Index
Fibre boards 341
Flat method of planting 81
flowering stimulus 48
fluazifop 304, 306, 307
fluff 249
fly ash 341, 362 '
fodder and feed 342
foliar spray 222
Foundation seed 252
freckling 173, 224
Fusarium 345
fusilade 304
fusilade super 304
G
gamma BHC 131 gasohol 352
genetic contribution 288
Genetically modified Herbicide Tolerant
(GmHT) 256,257
Gigaspora 158
Glomus 158
Glomus mossae 158
glyphosate 306
Gramaxone 50,314
Grass Shoot Disease (GSD) 250
green cane harvesting 314
Green leaf manuring 75
green manure crops 104, 112
Greenhouse effect 299
Greenhouse gases .(GHGs) 70
Groundnut 320
growing degree days' 306
H
hand stripper 312
Handpicking 273
haploids 288
Harvest Index (HI) 27
heat units 29
Helminthosporioside 284
Helminthosporium 345
herbigation 202
heterotoxicity 240
Hibiscus cannabinus 320
High Fructose Corn Syrup (HFCS) 3, 324
High Test Molasses 352 Hot air treatment 251 Hot Water Treatment (HWT) 252 Hugot formulae 310 humidities 66 Hurricanes and typhoons 69 Hydrogenases 367
I IA clones 335
ideotype 347
IISR 8626 technique 91
imbibition 401
Imperata cylindrica 266
incineration 370
Income Equivalent Ratio 110
India intercropping 112
input of protons 102
Integrated Disease Management 268
Integrated Nutrient Management (INM) 242
Integrated Pest Management 268 Integrated Technology Transfer 372 intercropping 113
465
Sugarcane in agriculture and industry
internal drainage 203 International Sugar Agreement (ISA) 4
intertillage 265
invasiveness 267, 288, 346
invertase 301, 303
Iron chelates 222
Irrigation Use Efficiency (IUE) 191
itaconic acids 354
J
Jaggery 318
Java Ratio 307
K
K - H 2 0 index 164
Kaakavi or Kakumbi 327
kappa number 336, 338
Kenaf 340
Khandasari 323
KHS 2045 47
Kranz syndrome 330
L
l/d ratio 338
Lactic acid 354
Lactobacilli 336, 338
lalas 128
Land Equivalent Ratio (LER) 115
leachates 145
Leaf Protein 344
leaf rolling index 193
leaf water potential 0FL) 193
legumes 111
Leuconostoc 313
Light Interception (LI) 22 7
Light Use Efficiency (LUE) 227
lignocellulose 334
Lime Requirement 102
liming materials 102
liquid jaggery 323, 327, 328
liquid manure 371
Liquid mulch 237
loading 310
lodging 97
losses 374
low pressure nozzles 198
luxury consumption 159
Lysine 354
Lysol 285
M
Malabar pump 99
manchas blanchs 98
Marginal Benefit Cost Ratio 110
massecuite 433, 435
mature pineapple 284
mechanised cultivation 77,314
mechanistic models 293
Mechanized harvesting 314
Mesta 340, 398
methane 360
methyl bromide 286
microclimate 69, 330
micropropagation 391, 397
Microtube system 201
mill extraction 405
mill sanitation 409
minimum tillage 53
Miscanthus floridulus 16
Misri 324
466
Index
Mitscherlich equation 126
Modified Growing Degree Days
(MGDD) 65
Modified trench 86
Moist Hoc Air Treatment (MHAT) 252
molasses 434
molasses toxicity 355
Mole drains 99
monellin 2
monolithic crop 331
morphogenesis 390
mother liquor (molasses) 433
MRP 153
MS-I medium 395
MS-II medium 395
multiple effect 415
Murashige and Skoog medium (MS
medium) 391, 394
mushrooms 342
mycoherbicides 257
mycoplasmal 285
Mycorrhizae 157, 397
mycorrhizosphere 158
N
N cycle 138
Narenga 16
Natural alkaloids 393
Natural ripening 303
Neemcake Coated Urea (NCU) 131
Net Rendement 318
neutral invertase 301
New Guinea 15
newsprint 339
nimbidin 131
nimbin 131
nitrate reductase activity 171,221
Nitrogen cycling 130
Nitrogen harvest index (HIN) 27, 211
Nitrogen Use Efficiency (NUE) 126,
128, 129, 130, 134, 140, 171, 210, 221
noble canes 30
nomogram 56
non-centrifugal sugars 2
Non-flowering 311
non-sacchariferous plants 10,11
Number of Millable Canes (NMC) 77
Nutrasweet 325
Nutrient Balance Index (NBI) 181, 226
Nutrient modelling 296
•nutrient ratio 124
nyctiperiod 47
o organic mercurial compound. 281
outside glass 391
P
P-Solubilizing Microbes (PSM) 238
Paecilomyces lilacinus 187
paired-row planting 89, 90
parasites 278, 280
Parasuram axe 312
Partha method of planting 82
particle board(s) 341
pathogenic microorganisms 278
Pegasse soils 51
Pencillium 147
Pencillium digitatum 187
pentosans 338
467
Sugarcane in agriculture and industry
per capita 1 Phenyl Mercuric Acetate 284 phosphatase 303 Phosphaticum 216 photoperiod 47 photosynthetic rates 26 Photosynthetically Active Radiation
(PAR) 69
phyllochron 29
phytomass 348, 349
phytosiderophores (PS) 137
phytotoxicity 260
picolines 353
piping 128, 334
Pit planting 88
pithiness 334
Plant Growth Regulating substances
(PGRs) 137, 138
Pleurotus 358
Pol Ratio (PR) 229, 308
polybag seedlings 94
Polyethylene glycol (PEG) 290
polyurethane 2
Pongamia 147
porosity 72
Post harvest deterioration 313
power cane 360
power function 126
Prasada 324
pre-fertilizing 250
pre-seasonal 78
pre-seasonal planting 109
predators 278, 279, 280
prefertilising 76
Press Mud (PM) 119,153,286,357
primary extraction 406
Primary Index (PI) 300
primary juice 401
primary tillage 72
Producer gas 341
Proper housekeeping 409
propping 97
protectants 264
Protein sweeteners 325
protozoa 364
Pseudomonas 138, 216
Pseudomonas striata 157, 187
PSM 155
puddling the soil 272
puparia 275
pyridines 353
pyrilla epidemics 274
pyrites 105
Pythium graminicola 138, 186
R
Rab 323 Radiation Use Efficiency
(RUE) 68, 294
Radiobacter 147
Rajoeng method 84
Ratoon chlorosis 207, 222
Ratoon Stunting Disease (RSD) 250
Ratooning Ability (RA) 233
Rayungan method 84
Rayungans 84, 85, 266
Readily Available Water (RAW) 70
Recoverable Cane Sugar method 310
Reducing Sugars 318
Regur 53
468
Index
relay cropping 85, 106
Rendzina 51
residual action 260
residual herbicides 257
Rhizobacteria 137, 186
Rhizodeposition 135
rhizosphere 135, 209
Ridges and furrows 95
Rind hardness 23
Ring system 92
Ripeners 311
ripeness to flower stage 47, 48, 50
Ritter process 338
Roselle 398
Rotten bagasse 337
RUBISCO (Ribulose 1,5-biphosphate
carboxylase-oxygenase) 128, 133, 3
runners 284
s 5. officinarum 18, 26
S. sinense 16
S. spontaneum 16, 26
saccharin 325
Saccharobacter nitrocaptans 138
Saccharomyces cerevisiae 356
Saccharum barbari 17
Saccharum officinarum 17
Saccharum sinense 17
Saccharum sp. 17
Saccharum spontaneum 23
Sacrolin 346
safeners 267
Sakti Sugars 314, 315
Salaha Samitis 373
Saline soils 103
sandovit 280
sarkara 14
Sclerocystis 158
Sclerostachya 16
seblang 84, 85
Seblang or sprouted bud 84
second degree polynomial 126, 151
secondary juice 401
secondary tillage 72
self-ploughing 53
semi-aerobic 363
Sensitivity Index (SI) 263
serpentine method of furrow
irrigation 199
Sesbania 111, 147, 398
Sesbania rostrata 111
sett roots 24
Shakkar 324
shoot roots 24
Short Duration (SD) varieties 43
shoulder breaking 229
Side shooting 271
siderophores 138
silicate material 224
siliciferous plants 173
Silicon 223, 303
Single buds 87
Single Cell Protein 344, 355
SJM formula 308
Skip-furrow planting 89
skipped/alternate furrow irrigation 199
slops 350, 359, 367
slow N release fertilizers 131
Sludge 367
469
Sugarcane in agriculture and industry
smother crops 256
smut 250
Sodium Adsorption Ratio (SAR) 57, 103
sodium tetraphenyl boron (NaTPB) 162
soil biota 54
Soil compaction 55
Soil drenching 281
Soil Organic Matter (SOM) 56
Somatic hybridization 393
sooty moulds 275
Soyabean 320
Spaced Transplanting technique
(STP) 93, 94
sparse flowering 43
Specific Leaf Nitrogen (SLN) 228
spent wash 367, 368
Spontaneum plasma 232
Sport 397
spring planting 78
Sprinkler irrigation 198
square root 126
SS activity 303
stale cane 310
stalk logging 180, 193
Statutory Minimum Price
(SMP) 375, 377
steam consumption 427
Stevia rebaudiana 11, 327
Steviosides 327
Steviron 327
stillage 350, 359, 367
Streptomyces 216
Stress Index (SI) 298
strike point 320
strip tillage 74
stubble root 207
stubble shaving 229, 271
sucking pest 274
sucralose 325
sucrolin 333
Sucrose 2, 29
sucrose loader 304
Sucrose Phosphate Synthase 301
Sucrose Synthase (SS) 29, 300, 301
sugar beet 3, 10
Sugar Cess Act 1982 376
Sugar Control Order 375, 376
Sugar Development Fund (SDF) 376
Sugar exports 7
sugar factories 5
Sugar Pricing Board (SPB) 377
sugar yields 374
Sugar-paper-alcohol-power
complexes 398
sugarcane model 299
Sugarcane trash 139, 342
Sugarcane varieties 41
sulphur 105
sulphur burner 428
sulphur dioxide 413
sunshine 67
super phosphate solution 411
surface active agents 264
surface drainage 203
Surfactants 264, 267, 280
Surge irrigation 201
surplus power 360
sum 78, 189
470
Index
Suspended Particulate Matter 367
sweet proteins 2
sweet sorghum 10
Sweetener Index 324
synchrony 243
synergistic 263, 264
synergistic or antagonistic 264
syrup 429
T
T. harzianum 187
T. viridae 187
tandem 401, 402
tassel 24
teepol 280
teleonomic models 293
teliospores 282
Telodrin 131
Terminator 292
terminator gene 292
tetracycline 292
thaumatin 2, 325
thermal time 295
thermotherapy 281
thiram 283
third dewlap 180
threshold 269
Tilah lands 88,105
tissue culture 378, 391
Tjeblock method 85
Torula yeast 355, 356
Torulopsis utilis 356
Totipotence 397
tractor-drawn mechanical planters 96
Transfer chamber or hood 397
Transgenic 290 transgenic cane 267 transgenic herbicide tolerant plant 257 Translocative herbicides 257 trash 230,237, 241,343 trash twisting 97
Trench or Java method of planting 81 Trichoderma reesei 346 Trichoderma viridae 74, 147, 187, 237,
345,358 Trichogramma japonicum 269 Turbo tape system 201 twilight photosynthesis 330 Tyndallization 396
u Ultra-Low-Volume sprayers (ULV) 267
Urea Super Granules (USG) 131, 212
uromol 356
USWB Pan evaporation (EO) 191
V
vacuum pan 429 VAM fungi 286 Varieties 30 vermicompost 149 Vermicomposting 148, 149 Vesicular-Arbuscular Mycorrhizae
(VAM) 157, 158, 188,216
Vinasse 351, 359, 360, 367
Vinhoto 359
Vitavax 281
w Water hyacinth 364
water shoots 270
471
Sugarcane in agriculture and industry
water shoots (bull shoots) 128
Water Use Efficiency (WUE) 192, 235,
236
waterlogged conditions 270
Waxes 358, 359
Weed-free environment 251
weediness 267, 288, 346
wet feet 203
wet planting 95
wetting agents 264
whip 282
white patches 281
wild rodents 275
Winter and Carp 310
Winter and Carp formula 308
Wrapping and propping 97
X
Xanthomonas 138
Xylitol 325, 346
Y
Yeast(s) 350, 356
yeast sludge 356, 359
yield decline 20, 21
yield declining factors (FY) 231
yield gap 7, 9
yield plateaus 298
z Zymomonas mobilis 350, 353
472
Sugarcane cultivation and jaggery making is one of the oldest
occupations in India, strengthening the rural economy. With the
passage of time, great strides have been made in improving the yield
and quality of sugarcane. The percapita consumption of sugar has
nearly doubled since independence. Keeping in pace with the demand,
there has been a phenomenal increase in the number of sugar
factories in the country.
Sugarcane in Agriculture and Industry is written in the backdrop
of this scenario. It is meant to be a complete handbook for students,
teachers, planners, administrators, farmers, sugar industry personnel
and the general elite interested in the sweet crop.
The book deals with future farming of sugarcane and sugar processing
to meet the demands of 21st century. Emphasis is placed on precision
agriculture through simulation models and transgenics with
environmental safety.
An introductory chapter on sugar manufacture, the inclusion of
glossary, comprehensive bibliography and subject index have added
value to the book and enhanced its readability.
The emphasis on practical implications such as different planting
methods, manurial and harvest schedules makes the book
informative, instructive, engaging and worth reading.
PRISM BOOKS PVT LTD Bangalore
ISBN: 81-7286-149-4 Price: Rs. 950/-