SOIL PHYSICAL CONSTRAINTS AND THEIR MANAGEMENT

Tamil Nadu state with an area of 1,29,951 Sq.Km. lies at 80 5' and 130 40' North

latitude and 760 15' and 800 70' East longitude, with a warm climate and located in the east of the

Western ghat and has a gradual slope to the east extending upto the low hills of the Eastern ghats.

Physiographically it is divided into (i) The Coastal plain (ii) the Eastern ghat (iii) The plateau

area and (iv) The Western ghat.

The coastal plain stretches about 992 Km. from Pulicate lake to Cape Comerin with

three sub regions viz., the Northern plain, the Cauvery delta zone and the Southern plain. It is

about 86 to 96 Km. wide with an average elevation of 80 m. The Northern plain comprises of

Chingleput , a major part of South Arcot, the eastern part of North Arcot and Northern part of

Trichi districts. The Cauvery delta zone consists of Tanjore and part of Trichi, where as the

Southern Coastal plain is shared by Ramnad, Thirunelveli and Kanyakumari districts.

The Eastern ghat area between the rivers of Palar and Cauvery and the Coastal plain is

balked by discontinuous lines of hills, the Javed, Sherveroys, Kalrayon, Pachaimalai and Kolli

malai. North of the Palar river, smaller or even more broken hills are linked with the tails of

Guddapah in the Nagari hills. Across the Cauvery, further detached leads on to the long

Varashanad, Audipatty range and then to Cardomam hills. This line of discontinuous hills are

known as The Eastern ghat.

The area between the Eastern and Western ghat lies the Plateau area with elevation

ranging from 170 to 650 metres. Hence the topography is undulating. The Plateau is fringed on

the west by a group of hills known as Western ghats. On either side of the Palghat gap, the

highest mountains of the Peninsula dominates. They are the Nilgiris in the north and the

Anamalai, Palani and Cardomam hills in the south.

Soils of Tamil Nadu

The soil of Tamil Nadu are highly heterogeneous having different parent materials of

metamorphic, sedimentary, acid igneous rocks rich in soda lime feldspars, amphiboles and

pyroxenes of gnessic rocks, chernochites and sand stones. Thus it endowed with the collection of

five major soil order viz., Alfisol, Entisol, Vertisol, Inceptisol and Ultisol. Therefore it opens

avenue to carry out diversified research on physico chemical properties and also biophysical

1

properties at greater length and breadth. The total geographical area of Tamil Nadu is about 13

m.ha, out of which 8 m ha of the soils are of red in nature, 2 m.ha alluvial, 2 m.ha black and the

rest lateritic. Because of the diversified nature, characterised by their different origin, location

and soil forming processes, these soils are found to possess various types of soil constraints.

The plant nutrient availability in soil is a measure of soil fertility, while the soil

physical environment is the kingpin which regulate the retention and movement of soil moisture,

soil aeration, soil nutrient movement, soil temperature, seed germination, seedling establishment,

root penetration and proliferation etc. Hence, soil physical environment directly and indirectly

controls all the other factors influencing the plant growth and in turn the production potential of

the crop.

Recently, under the fold of Integrated Nutrient Management technique, organic and

Integrated Farming System, an attempt has been made to increase the crop production under

rationalised plant nutrient management, where the management of physical condition plays a

pivotal role. Besides by ameliorating certain physical constraints existing in the marginal and

submarginal lands, it would be easier to enhance the production potential of the crop in an unit

area. Knowingly or unknowingly, the poor soil management, unexpected natural calamities

often affect the soil environment and arrest its productivity. By judicious application of all the

required plant nutrients at times fail to yield good results. It might be due to unforeseen weather

conditions like heavy rain, stagnation of water, long dry spell or continuous cultivation which

finally affects the physical environment like infiltration, moisture retention and transmission, soil

compaction and aggregation leads to soil physical constraints constantly.

The most frequently occurring soil physical constraints in the state of Tamil Nadu are

excessive permeable soils, sub soil hardpan soils, slow permeable soils, fluffy paddy soil, surface

crusting and shallow soils. The nature and extent of the soil physical constraints in the soils of

Tamil Nadu are not delineated by the staff of Soil Survey and Land Use Planning and hence, one

of the major objectives of the AICRP on "Tillage Requirements of Major Indian Soils under

Different Cropping Systems" is to characterise the major soil series of Tamil Nadu for their

physical constraints. In Tamil Nadu, so far six districts viz., Coimbatore, Salem, Dharmapuri,

Trichi, Madurai and North Arcot were surveyed for identifying the areas having soil physical

constraints and suitable technologies were developed and test verified in farmer's holdings

continuously for more than three years. The following are the major soil physical problems

commonly met with in Tamil Nadu.

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Table 1 Delineation of physical constraints in the soils of Tamil Nadu state

Soil series Area in Problemssq.km. Identified Per cent

Coimbatore district

PeelameduDasarapattyPerianaicken 739 Slow permeable 4.69palayam soils

IrugurPalladam 6,519 Excessively Vannapatty permeable soils 41.82

Tulukkanur 1,320 High sub soil Pichanur bulk density 8.46

DharmapuriDharmapuriNattam Slow permeableHosur 526 soils 5.47

Vannapatty 3,774 Excessively 39.24permeable soils

TrichiIrugurTulukkanurPalladam 2,800 Excessively 32.00Vannapatty permeable soils

PeelameduKallakudiPoovalur 1,243 Slow permeable 14.20Mudukulam soils

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Soil series Area in Problemssq.km. Identified Per cent

Madurai district

Anaiyur SubsoilMadukkur 2,450 compaction 30.0

Irugur 1,837 Excessively 22.5Palladam permeable soils Salem district

Irugur Mallasamudram ExcessivelyMallur 1,845 permeable soils 21.35

Peelamedu 420 Slow permeable 4.85soils

Vellalur 209 Shallow soils 2.45

North Arcot district

Udic Haplustalf 1,448 Sub soil 17.61Typic Rhodustalf hardpan

Typic Ustifluent 524 Excessive 6.37permeable soils

Typic Ustorthents 384 Shallow soils 4.67

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The consolidated survey report of the Tamil Nadu is presented in Table 2.

Table 2 Extent of soil physical constraints in Tamil Nadu

Total Geographical Area = 130 lakh ha.

Districts Area Excessive Slow Subsoil Shallowpermeable permeable hardpan soilssoils soils soils

Coimbatore 15.8 6.5 0.7 1.3 -

Dharmapuri 9.6 3.8 0.5 - -

Trichi 8.8 2.8 1.2 - -

Madurai 8.2 1.8 - 2.5 -

Salem 8.6 1.8 0.4 - 0.2

North Arcot 8.2 0.5 - 1.5 0.4

Total 59.2 17.2 2.8 5.3 0.6

% surveyed 45.5

% to surveyed area 29.3 5.0 8.8 1.0

The common soil physical constraints often encountered in Tamil Nadu are · Sub soil hard pan· Excessive permeability· Surface soil crusting · Fluffy paddy soils· Slow permeability

Out of the total area of the state (130 lakh ha.) 45.5 per cent was surveyed out of

which, 29.3 percent of the surveyed area was found to possess excessive permeability, 5.0 per

cent slow permeability, 8.8 per cent sub soil hard pan and 1.0 per cent are shallow soils. The

results also indicated that the most of the soil physical constraints viz., the excessive

permeability, sub soil hardpan and shallow soils, which are associated with red soils, are

predominant in the soils of Tamil Nadu owing to the fact that about 60 per cent of the soils of

Tamil Nadu belong to this category. The characteristics of the soils possessing soil physical

constraints, extent and their management practices are briefly discussed here under:5

Excessive permeable soils

Excessive permeable soils are those having high amount of sand exceeding 70 per

cent. Due to this, the soil is inert and unable to retain water and nutrients. These soils being

devoid of finer particles and organic matter, the aggregates are weakly formed, the non-capillary

pores dominating with very poor soil structure. Due to low retention capacity of the soils, the

fertilizer nutrients are also lost in the drainage water.

The excessive permeable soils are spread over 6,519 sq.km in Coimbatore, 3,774

sq.km in Dharmapuri, 2,800 sq.km in Trichi, 1,837 sq.km in Madurai, 1,845 sq.km in Salem and

524 sq.km in North Arcot districts. The excessive permeable soils can be managed by adopting

the techniques given below:

· Compacting the field with 400 kg stone roller (tar drum filled with 400 kg of sand or stone

can also be used) 8 - 10 times at optimum moisture conditions.

· Application of clay soil (Soil Breeding) up to a level 100 t ha-1 based on the severity of the

problem and availability of the clay material.

· Application of organic materials like farm yard manure, compost, press mud, sugar factory

slurry, composted coir pith, sewage sludge etc.

· Providing asphalt sheet, polythene sheet etc., below the soil surface to reduce the infiltration

rate.

· Crop rotation with green manure crops like Sunnhemp, Sesbania, Daincha, Kolinchi etc.

Sub soil hard pan

The sub soil hard pan in red soil is due to the illuviation of clay to the sub soil horizon

coupled with cementing action of oxides of iron, aluminum and calcium carbonate, which

increases the soil bulk density to more than 1.8 Mg m-3. Further, the hard pan can also develop

due to continuous cultivation of crops using heavy implements upto certain depth constantly.

Besides, the higher exchangeable sodium content of clay complex in black soil areas also resulted

in compactness of the sub soil. All put together lowered the infiltration and percolation rates,

nutrients movement and free air transport within the soil profile. It prevents the root prolifera-

tion and limits the volume of soil available for nutrient uptake resulting in depleted, less fertile

surface soil. Due to this, the contribution of sub soil fertility to crop growth is hampered.

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The sub soil hard pan areas are found in 1,320 sq.km in Coimbatore, 2,450 sq.km in

Madurai and 1,448 sq.km in North Arcot districts. Depending upon the depth of occurrence of

hard pan, the management practices are to be adopted. Hence for soils having sub soil hard pan

at shallow depth, the following technologies could be adopted.

· Ploughing the soil with chisel plough at 0.5 m interval criss cross at 0.5 m depth once in 2-3

years.

· Application of organics to improve the aggregation and soil structure so as to prevent further

movement of clay to the lower layers.

· Deep ploughing of the field during summer season to open up the sub soil.

· Cultivating deep rooted crops like tapioca and Cotton so as to encourage natural breaking of

the hard pan.

· Raising deep rooted semi perennial crops like mulberry, jasmine match wood tree etc., can

also help in opening up the sub soil hard pan.

Slow permeable soils

Slow permeable soils are those soils having infiltration rates ranging from less than 6

cm per day due to high clay content of the soil. Due to low infiltration rates, the amount of water

entering the soil profile is reduced thus increasing the run-off. Further, it encourages erosion of

surface soil leading to nutrient removal in the running water. More over, due to heavy clay

content, the capillary porosity is relatively high resulting in impeded drainage and reduced soil

conditions. This leads to increase of some soil elements to the level of toxicity to the plants. It

also induces nutrient fixation in the clay complex thereby making the nutrient becoming unavail-

able to the crop, eventually causing deficiency of nutrients.

The results of the work carried out in the scheme had indicated that the slow

permeable soils extended over an area of 739 sq.km in Coimbatore, 526 sq.km in Dharmapuri ,

1243 sq.km in Trichi and 420 sq.km in Salem districts. The constraints in such soils can be

managed by adopting suitable management practices like,

· Provision of drainage facilities either through open drains or closed sub surface drains.

· Forming contour bunding and compartmental bunding to increase the infiltration rates of the

soils.

· Application of huge quantities of river sand or red soils of coarser texture to dilute the

heaviness of the soil.

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· Application of liberal doses of organic manures like farm yard manure, compost, green

manure, composted coir pith, sewage waste, press mud etc.

· Adopting ridges and furrows, raised beds, broad bed and furrow systems of irrigation.

· Application of soils conditioners like H-concentrate, vermiculite, Jalasakti etc., to reduce run-

off and soil erosion.

Shallow soils

The shallow soils are characterised by the presence of the parent rock immediately

below the soil surface at about 15 - 20 cm depth. This restricts the root elongation and

spreading. Hence the crops grown in these soils necessarily be a shallow rooted crops, which can

exhaust the soil within 2 - 3 seasons. There fore frequent renewal of soil fertility is a must in

these soils.

Among the six districts surveyed, the shallow soils are prevalent in a notable

proportion of 209 sq.km. and 384 sq.km. in Salem and North Arcot districts respectively. These

soils can be managed by growing crops which can with stand the hard rocky sub soils like

Mango, Ber, Fig, Country goose berry, West Indian cherry, Anona, Cashew, Tamarind etc.

Technologies for soil physical constraints, demonstrated to the farmers through field

experiments

The various technologies like chisel technology for sub soil hard pan soils, compaction

technology for the soils having excessive permeability and fluffyness, and other management

practices to overcome the slow permeable soils, surface crusted soils in addition to the

technologies developed are demonstrated to the farmers through field experiments and on farm

trials. The details of soil characteristics, extent, technologies and the results of experiments

conducted are detailed below.

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Chisel technology for sub soil hard pans

In Tamil Nadu, red soils (Alfisols) occupy 8 million hectares which constitutes 62 per

cent of the total geographical area. The occurrence of hard pan at shallow depths is the major

prevalent soil physical constraints in these soils. The agricultural crops are not able to enjoy the

full benefits of the soil fertility and nutrient use due to this major cause. The reasons for the

formation of sub surface hard pan in red soils is due to the illuviation of clay to the sub soil hori -

zons coupled with cementing action of oxides of iron, aluminium and calcium carbonate. The

sub soil hard pan are characterised by high bulk density (>1.8 Mg m-3) which in turn lowers

infiltration rate, water holding capacity, available water and movement of air and nutrients with

concomitant adverse effect on the yield of crops.

Technology to overcome sub soil hardpan

To eradicate the problems of sub soil impervious layer in red soils, many trials were

conducted in farmer's field / Tamil Nadu Agricultural University farms with chisel plough, which

proved effective than any other implements in successfully break opening of the hard pan, there

by helped to facilitate better root growth, nutrient and water movement with concomitant

increased productivity.

Methodology

· The field is to be ploughed with chisel plough at 50 cm interval in both the directions.

· Chiselling helps to break the hard pan in the sub soil besides it ploughs up to 45 cm depth.

· The farm yard manure or press mud or composted coir pith at 12.5 t ha-1 is to be spread

evenly on the surface.

· The field should be ploughed with country plough twice for incorporating the added

manures.

· The broken hard pan and incorporation of manures make the soil to conserve more moisture

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Experimental results

Field experiments were conducted using chisel plough under rainfed and irrigated

conditions and the results are furnished hereunder.

The results of the experiment conducted in farmer's holding at Kande Kounden

Chavadi (Pichanur soil series) with sorghum as the test crop indicated that chiselling at 0.5 m

interval and 1 m interval being on par recorded higher grain yield (Table 3).

Table 3 Effect of chiselling on the grain yield of sorghum (Mg ha-1) and soil physical

properties

Treatments Bulk density Hydraulic conductivity Grain Yield

(Mg m-3) (cm h-1) Mg ha-1

Chiselling(0.5m apart) 1.42 11.9 4.72

Chiselling(1.0m apart) 1.45 9.7 4.08

Chiselling(1.5m apart) 1.58 9.1 3.71

Unchiselled 1.65 5.2 3.42

The effect of chiselling was much realised in the residual crop than the first crop

(Table 4). The effect of chiselling at closer interval was spectacular as could be seen from the

yield data of second crop compared to chiselling at wider intervals. The experiments conducted

on both seasons clearly indicated the need for breaking the dense layer occurring at shallow

depth with closer intervals of chiselling for obtaining higher yield of sorghum crop.

Table 4 Residual effect of chiselling on the grain and straw yield of sorghum

Treatments Yield (Mg ha-1)

Grain Straw

chiselling (0.5 m apart) 4.48 20.37

chiselling (1.0 m apart) 3.91 14.00

chiselling (1.5 m apart) 2.51 11.22

Unchiselled 1.37 9.22

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In order to evaluate the efficacy of chisel plough with other tillage implements

commonly used by the farmers in soils having hardpan, a trial was conducted with tapioca as the

test crop and the results proved the superiority of chisel plough than the disc plough (Table 5)

Table 5 Comparative efficacy of chiselling on the tuber yield of tapioca

Treatments Tuber yield Bulk density (Mg m-3)

t ha-1 0-20cm 20-40cm 40-60cm

Chisel plough 53.79 1.527 1.666 1.635

Disc plough 49.46 1.564 1.698 1.692

Country plough 43.97 1.575 1.729 1.759

Similar trend of results were also obtained when groundnut was raised as the test crop.

Trials conducted with cotton as the test crop in farmer's holding at Valukkuparai of

Madukkarai block where the actual problem of subsoil hard pan exists. The results revealed that

chiselling at 0.5 m interval with application of composted coir pith at 12.5 t ha1- recorded 29 per

cent yield increase over unchiselled plots (Table 6).

Table 6 Effect of chiselling and composted coir pith on bulk density and kapas yield of Cotton

Treatments Cotton kapas Bulk density (Mg m-3)Yield 0-15 15-30 30-45

(q ha-1) cm cm cm

Unchiselled 7.8 1.552 1.714 1.745

chiselled(0.5 m apart) 9.5 1.513 1.548 1.745

chiselled + CCP 10.1 1.459 1.523 1.594

CCP = Composted coir pith @ 12.5 t ha-1

After the harvest of cotton, maize Co 1 and sorghum Co 26 were raised as first and

second residual crops. In both the crops, chiselling at 0.5 m apart with composted coir pith at

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12.5 t ha-1 recorded 21 and 15 per cent yield increase over the control respectively, revealing the

advantageous effect even for one or more residual crops.

The mobility of nitrogen and potassium ions was studied both in chiselled as well as in

unchiselled plots (Table 7). The nitrogen and potassium mobility were observed up to 45 cm

depth due to chiselling, whereas in the unchiselled plot (control) the N and K mobility was

restricted with the surface layer. Thus chiselling besides providing conducive physical

environment, helps in the nutrient mobility particularly N and K.

Table 7 Mobility of nitrogen and potassium ions in chiselled and unchiselled plots

Depth (cm) chiselled UnchiselledKMnO4-N NH4OAc-K KMnO4-N NH4OAc-K

kg ha-1 kg ha-1 kg ha-1 kg ha-1

0 - 15 217 213 224 342

15 - 30 226 303 210 190

30 - 45 236 118 172 69

45 - 60 150 64 145 56

With a view to demonstrate and to disseminate the chiselling technology large scale

demonstrations were conducted in Pichanur soil series. Demonstration plots in an area of 8 acres

were laid out in Kande Koundan Chavadi in farmer's field with rainfed sorghum Co.24 as the test

crop (Table 8) which proved the beneficial effect of chiselling to the farming community.

Table 8 Effect of chiselling on the yield of rainfed Sorghum

Treatments Grain yield Straw yield

t ha-1 t ha-1

Country plough 0.54 2.19

Chisel plough 0.82 2.69

The grain yield of sorghum was found to be higher in chiselled plot compared to

country ploughing treatment. The residual effect of chiselling was also studied in the same plots

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with Ganga 5 maize. The grain yield in chiselled plots was 3.27 t ha-1, while it was 2.69 t ha-1

under the unchiselled plots, proving the superiority of chiselling.

Demonstration trials for chiselling were also conducted with groundnut, blackgram,

maize tomato, samai as the test crops which again proved the beneficial effect of chiselling

technology.

Economics of chiselling

The field experimentation and On Farm Trial (OFT) results showed that chiselling at

0.5 m apart enhanced the yield of crops and improved the soil physical properties. However, any

technology could be successful only if the return by adopting it is economical. Hence the

economics of the chiselling technology was calculated for different crops.

The economics worked out for sorghum Co 23 showed that a net profit of Rs 1125

ha-1 could be obtained by adopting chiselling technology for loosening sub surface compact

layers (Table 9).

Table 9 Economics of chiselling in sorghum

Treatments Yield (t ha-1)Grain Straw Value (Rs ha-1)

Control 3.42 10.45 5,838Chiselling 4.72 13.51 7,964Increase over control 1.30 3.05 2,526Cost of chiselling - - 1,000Net profit - - 1,125

The economics of chiselling in tobacco crop is furnished in Table 10.

Table 10 Economics of chiselling in tapioca

Particulars Tuber yield (t ha-1) Value (Rs ha-1)Control 44.0 15,400Chiselling 53.8 18,830Increase over control 9.8 3,430Cost of chiselling - 1,000Net profit - 2,430

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The results showed that chiselling in the hard pan soils improved the tapioca tuber

yield by 22 per cent and there by resulting in a net profit of Rs. 2,430 ha -1. The economics of

chiselling was worked out for groundnut, blackgram and maize are given in table 11.

Table 11 Economics of chisel technology for groundnut, blackgram and maize

Crops Yield (t ha-1) Value of grain (Rs ha-1)

Unchiselled Chiselled Unchiselled Chiselled Net profit

Groundnut 1.34 2.18 4,704 7,642 2,240

Blackgram 0.39 0.64 1,584 2,591 308

Maize 2.10 3.27 4,620 7,190 1,870

The net profit ranged from Rs. 308 for blackgram to Rs. 2,240 ha-1 for groundnut crop.

The chiselling was more beneficial for groundnut crop by breaking the sub soil hard pan in red

soil, thus facilitates the peg formation.

Conclusion drawn from the chiselling experiments

· Reduces the bulk density by 0.2 to 0.4 Mg m-3.

· The hydraulic conductivity was almost doubled in sub soil i.e. below 15 cm to 45 cm depth.

· Conserves around 30 to 40 per cent more soil moisture.

· Roots proliferation is improved by 40 to 45 per cent.

· Nutrient mobility especially N and K increased by 20 to 30 per cent and 30 to 40 per cent

respectively to sub surface layers.

· Enhances the crop yield

1. Sorghum : 25 - 30 per cent2. Tapioca : 20 - 25 per cent3. Groundnut : 15 - 20 per cent4. Cotton : 25 - 30 per cent

· Residual effect can be realised for three seasons.

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Technology developed for excessive permeable soils

Sandy soils containing more than 80 per cent sand fractions occur in coastal areas,

river delta and in the desert belts. Such soils do occur in Coimbatore, Trichi, Kanyakumari,

Tanjore, Tirunelveli districts and in parts of coastal areas in Tamil Nadu. Delineation of areas

for soil physical constraints in Tamil Nadu focused that a total area of 14.93 lakh hectares were

affected by excessively permeable soils.

The nature of excessive permeability of the sandy soil results in very poor water

retention capacity, very high hydraulic conductivity and infiltration rates. So whatever the

nutrients and water added to these soils are not utilized by the crops and subjected to loss. In

addition, it is not providing anchorage to the crops grown.

Compaction Technology

To correct the textural weakness of these sandy soils and to make them suitable for

sound farming, various ameliorative measures have been devised by the scientists of Tamil Nadu

Agricultural University. Introduction of artificial barriers in the sub soil zone using asphalt,

bitumin and cement dust have been found to arrest the higher rate of nutrient and water losses in

sandy soils. But the prohibitive cost of sub surface barriers make practically unavailable to

farmers. So, for such soils compaction technology developed by Tamil Nadu Agricultural

University scientists proved to be very effective.

Methodology

· The soils should be ploughed uniformly.

· Twenty four hours after a good rainfall or irrigation, the soil should be rolled 10 times with

400 kg stone roller of 1 m long or an empty tar drum filled with 400 kg sand.

· Then, shallow ploughing should be given and crops can be raised.

Other management practices· Use of minimum and frequent irrigations.· Form minimum plot size.· Adopt more number of splits for fertilizer application especially for nitrogen and potassium.

Results from the field experiments15

A field experiment was conducted initially in the sandy soils of Tindivanam (South

Arcot district, North eastern zone) with groundnut as test crop. The soil was compacted from the

surface at 10 per cent moisture level by making 10, 15 and 20 passes of stone roller weighing

400 kg, after 24 hours and 48 hours of irrigation. The surface soil was then loosened by using a

country plough and groundnut was raised.

The results revealed that there was an increase in pod yield of Groundnut by 11 per

cent due to compaction of sandy soil with 15 passes of roller after 24 and 48 h of irrigation over

control. In addition, it increased the bulk density of the soil by 0.12 to 0.19 Mg m-3 and there by

resulting in reduced infiltration rate and hydraulic conductivity. For groundnut crop, the

compaction with 15 passes of stone roller after 24/48 h of irrigation was helpful in enhancing the

pod yields besides establishing good physical condition in soils.

In an another field experiment in farmer's field at Mankarai in Coimbatore district

(Western zone) with maize as the test crop, the compaction technology proved its benefit over

the existing method of cultivation. The infiltration rate of the soil was significantly reduced by

compaction (Table 12).

Table 12 Effect of compaction on Infiltration rate of the soil

Treatments Infiltration rate (cm h-1)

Control 14.88

10 passes 11.84

15 passes 10.40

20 passes 7.84

Compaction with stone roller in the field of high permeability was significantly

effective in increasing the bulk density (from 1.49 to 1.62 Mg m-3) and in reducing infiltration

rate (from 16.6 to 7.84 cm h-1), moisture retention from 7.71 to 10.62 per cent. As the number

of passes increased the bulk density also increased. However 10 passes of roller was sig-

nificantly superior in giving the highest grain and straw yields (36 and 39 per cent increase in

yield respectively over control). 16

In an another field trial conducted in farmer's holding at Veerapandipudur

(Coimbatore , Western zone) to test the compaction technology with sorghum as test crop. The

results showed that as the number of rollings increased, the bulk density was increased from 1.51

to 1.71 Mg m-3 in the surface layer of 0 - 15 cm depth and from 1.49 to 1.64 Mg m-3 in the sub

soil layers. The infiltration rate decreased from 32.0 for control plots to 11.2 cm h-1 in the plots

which received 12 passes of stone roller However, the highest grain yield of Sorghum (20 and 25

per cent over control) was obtained by passing of stone roller 9 times, after 24 h of irrigation and

6 times after 48 h of irrigation respectively. The treatments with 9 passes of stone roller after 24

h of irrigation appeared optimum for higher grain yield of Sorghum by increasing the bulk

density and lowering the infiltration rate.

Field experiments were conducted with groundnut (POL 2) crop in farmer's holding at

Veerapandipudur Coimbatore (Western zone) with 0, 5, and 10 passes of 400 kg stone roller after

24 h of irrigation as treatments. Increase in the levels of compaction, increased the bulk density

at all three depths with concomitant moisture retention from 5.85 to 7.39 per cent. Infiltration

rate was predominantly reduced to 59.79 cm h-1 from 70.66 cm h-1. Increased pod yield and

haulm yields were recorded (18 and 13 per cent over control) by compacting the soil with 400 kg

stone roller 10 times.

To test verify the compaction technology under rainfed conditions field experiment

was conducted with the test crop of groundnut followed by residual crop of tomato (Pusa ruby)

and groundnut (TMV 3) in the farmer's holding at Coimbatore. Half of the area was left

uncompacted and the other half was compacted with 400 kg stone roller 10 times, 24 hours after

a rain fall (Table 13)

.

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Table 13 Effect of compaction on crop yields (t ha-1)

Treat Main crop First residual Second residualment Groundnut Tomato Groundnut

Pod yield Fruit yield pod yield

Compacted 2.42 3.40 2.35

Uncompacted 2.02 2.95 2.11

The results indicated that in the first crop of Groundnut, the compaction technology

helped in enhancing the pod yield by 20 per cent over control (Table 13). The residual effect

was well reflected in the second and third crop of Tomato and Groundnut. Tomato - Pusa ruby,

the first residual crop gave 15 per cent increased yield and the second residual crop recorded 11

percent increased yield over the control. Thus it is very clear that compacting the soil by passing

400 kg stone roller 10 times is more advantageous for improving the crop yields, that apart, the

residual effect can be realised for three years. Similar types of responses to compaction was also

observed in maize followed by groundnut crop in cultivator's field at Veerapandy Pudur.

Conclusions from the compaction technology experiments

· Conserves more moisture (20 to 25 per cent).

· Prevent nutrients from leaching and retains in the surface layer upto 20 to 25 %, 5 to 10 %

and 25 to 30 % with respect to N,P and K)

· Enables better seed soil contact

· Enhances the yields of main and residual crops

1) Groundnut : 15 - 20 per cent

2) Maize : 25 - 30 per cent

3) Sorghum : 20 - 25 per cent

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Compaction technology for fluffy paddy soils

In Tamil Nadu fluffy rice soils are prevalent in Cauvery delta and in many parts of the

state due to the continuous rice - rice cropping sequence. The traditional method of preparing the

soil for transplanting rice consists of puddling, which results in substantial break down of soil

aggregates into a uniform structureless mass. Under continuous flooding and submergence of the

soil for rice cultivation in a cropping sequence of rice - rice - rice, as in many parts of Tamil

Nadu, the soil particles are always in a state of flux and the mechanical strength is lost leading to

the fluffiness of the soils. This is further aggravated by in situ incorporation of rice stubbles and

weeds during puddling. This causes sinking of draught animals and labourers during puddling.

This has been thus, an invisible drain of finance for the farmers due to high pulling power needed

for the bullocks and slow movement of labourers during the puddling operations. Further the

fluffiness of the soil lead to very low bulk density and thereby leading to very rapid hydraulic

conductivity and in turn the soil does not provide a good anchorage to the roots and the potential

yield of crops is adversely affected.

Technology

In Tamil Nadu due to continuous and intensive cropping of rice. Puddling poses a big

problem of sinking of draught animals and labourers to more than knee deep. Hitherto the only

remedial measure adopted by the farmers was engaging very light animals like the Umbalachari

breeds. Now big and heavy Kangayam breeds are engaged for puddling operations which further

aggravated the problem and hence to prevent the sinking, compaction technology was developed

by the scientists of Tamil Nadu Agricultural University.

Methodology

· The irrigation should be stopped 10 days before the harvest of rice crop

· After the harvest of Rice, when the soil is under semi - dry condition (proctor moisture level), compact the field by passing 400 kg stone roller or an empty tar drum filled with 400 kg of sand 8 times.

· The usual preparatory cultivation is carried out after compaction.

Results from the field experiments

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To overcome the fluffiness in rice fields, a field trial was conducted with rice (Paiyur-

1) in wet lands, Tamil Nadu Agricultural University farm, Coimbatore. The treatments imposed

were preparatory cultivation under dry condition after compacting the field with 400 kg stone

roller by passing 8 and 16 times. The results exhibited that 8 passes of roller was optimum for

compacting the soil, besides increasing the yield of rice grain by 35.5 per cent over control,

where preparatory cultivation was done under dry condition, the increase was only 31.4 per cent

under puddled condition.

Another field trial with rice (Ponmani) as test crop in wet land was carried out. The

treatments imposed were compaction by passing 400 kg stone roller 8 times and application of

gypsum at 2 t ha-1. Compaction increased the grain yield of ponmani by 17.8 per cent over the

control. Second crop of rice (IR-50) was sown in the same plot to study the residual effect of

compaction. Yield of rice in the compacted puddled field was enhanced by 10 per cent over the

control.

Soil surface crusting

In Tamil Nadu, soil moisture is a very serious constraint in dry belts, but even the

small amount of rainfall received is capable of developing the surface crusts. This problem is

prevalent mostly in red soil areas (Alfisols) and is of greater magnitude in districts like Trichy,

Pudukottai, Ramnad and Tirunelveli. Surface crusting is due to the presence of colloidal oxides

of iron and aluminum in Alfisols which binds the soil particles under wet regimes. On drying it

forms a hard mass on the surface. The surface crusting results in the prevention of germinating

seeds, retardation of root growth, poor infiltration increased surface run off and poor aeration in

the rhizosphere.

Results of the field Experiments

A field trial with greenroom was conducted by applying different levels of farm yard

manure and lime at National Pulses Research Center, Vamban, Pudukottai District (Table 14).

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Table. 14 Effect of FYM and Lime on the physical properties of soil and yield of Green gram

Treatments Grain yield Bulk density Total porosity

t ha-1 Mg m-3 Per cent

Lime at 2 t ha-1

+ 0.24 1.45 40.3

FYM at 10 t ha-1 Control 0.20 1.48 39.7

Combined application of lime and farm yard manure enhanced the yield by 20 per cent

over control besides improving the physical properties of the soil.

In an another experiment with organics application to mitigate the surface crusting

problem, application of gypsum at 10 t ha-1 recorded the highest grain yield of cowpea (35 per

cent increase over control) closely followed by sheep manure application. The lowest yield was

recorded in the control plots.

Management of slow permeable soils

Delineation work carried out in Tamil Nadu exposed that 14.32 lakh hectares of land

are affected by slow permeable soils. Slow permeable soil is mainly due to very high clay

content and poor drainage conditions which results in poor aeration and water stagnation and

ultimately leads to poor crop growth and in certain cases leads to complete death of crops.

Results from the field experiments

A field experiment was conducted with sorghum Co.24. employing different cultural

methods, the highest grain yield of sorghum was obtained from the raised bed plots, followed by

sowing on the ridges, while the least yield was recorded from the flat beds. The second crop of

Cotton MCU.9. raised in the same plots, the results showed that the flat bed system was superior

by registering the highest yield (1.02 t ha-1)

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Addition of organics namely FYM / Composted coir pith / press mud at 12.5t ha-1

found to be optimum for the improvement of the physical properties besides, it facilitates water

movement to the root zone.

For rainfed crops ridges are formed along the slopes for providing adequate aeration to

the root zone. Interception drainage channels should be provided to carry the excess water to

rice fields located at lower end of the slope.

The bulk density was found to be reduced due to increase in non-capillary pores in

upper 10 cm layer of raised bed besides increase in yield of crops by forming raised and sunken

beds.

To reduce the amount of water retained in black clay soils during first 8 days of

rainfall, broad beds of 3 - 9 m wide should be formed either along the slope or across the slope

with drainage furrows in between broad beds.

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