Agric.Re~,23(2): 110-126,2002

SALT-AFFECTED SOILS AND THEIR MANAGEMENTFOR SUSTAINABLE RICE PRODUCTION -KEY MANAGEMENT ISSUES : A REVIEW

R. ChhabraDivision of Soil and Crop Management,

Central Soil Salinity Research Institute, Karnal-132001, India

ABSTRACTRice is a major cereal crop of India and many other countries in the world. Reclamation of

2.359 m ha alkali soils out of 8.373 m ha of salt-affected soils holds promise for an additionalarea to inc.rease rice production in developing countries like India. A package of practices consist­ing of proper on farm development, application of amendments, appropriate agronomic practicesincluding fertilizer application have been evolved to get 4 to 7 t ha- 1 of rice in alluvial alkali soils.To maintain productivity of salt-affected degraded soils it is important to manage these soils insuch a way so as to prevent their resodication, sustain their physical and chemical properties andfertility status. Due to low use of fertilizers and organic manures, and imbalance application ofnutrients there is a decline in fertility of reclaimed alkali soils. Post-reclamation management ofnutrients in these soils is very crucial to sustain rice production. A major part of the rice growingarea is suffering due to declining water table affecting yields and escalating costs of pumpinggroundwater from deeper depths. Changes in agronomic practices like banning of summer rice,delayed transplanting and better management of irrigation water are required to save groundwa­ter, arrest falling water table and to prevent deterioration in its quality. Storing rainwater in theexisting paddy fields and allowing it to seep through the soil is a natural, viable and practicalsolution for recharging the groundwater. Irrigation should be so planned as to avoid water stressin rice during its reproductive growth phase to minimize sterility.

To provide for an increasing popula- and managed in such a way so as to providetion of an estimated 1000 million, India has to additional area for increasing food productionincrease its grain production manifold. Assured in the country. It is estimated that salt-affectedirrigation and an increased area under irriga- soils occupy nearly 7 per cent of the world landtion from 22.6 million ha in 1950-55 to 99.3 area (Dudal and Purnell, 1986). Massoudmillion ha by the end of the 8th Five Year Plan (1974) estimated this area as 932 million ha,(1992-97), greater and balanced use of fertil- of which 316 million ha are in the developingizers, integrated pest management and devel- countries. Based on the estimates prepared byopment of high yielding varieties have helped Singh (1992), out of 8.373 million ha of salt­in increasing its grain production from 195.48 affected soils in India, 2.359 million ha are al­million tons during 1989-91 to 223.01 mil- kali, 3.829 million ha are saline while the re­lion tons in the year 1997 (FAO, 1998). Rice maining 2.185 million ha are coastal salinealone has contributed more than 55% of the soils. In India these soils are mostly found intotal cereal production (Table 1). It must be the states of Uttar Pradesh (U.P.), Haryana,emphasized however, that area under rice has Punjab, Madhya Pradesh (M.P.), Bihar, Andhranot increased during this period, remaining Pradesh (A.P.), West Bengal, Orissa and Tamilstatic at 42 million ha. Considering the limita- Nadu. These soils, hitherto considered as waste­tion of these methods and pressure on good lands, have a potential to increase area underland for other uses, there is a limited possibil- rice, wheat and other crops. Recent scientificity to further increase rice production. Hence innovations have made it possible to reclaimsoils, which were earlier considered unsuitable large areas of these degraded soils for increas­for agricultural production, have to be reclaimed ing grain production in India.E-mail address: rchhabra@cssri.ren.rikin

Vol. 23. No.2. 2002

Table 1. Area and production of cereals and rice in India.

111

Year

Total area harvested. m haTotal cereal production, m tArea under rice, m haRice production, m t

1989-91

102.27195.48

42.50111.29

1995

100.18214.3642.91

119.44

1996

100.00217.98

42.80121.81

1997

9993223.0142.20

123.01

Further, in canal command areas about2.46 million ha which were earlier under dryland agriculture have turned waterlogged andhave to be used for raising low land crop suchas rice. This study looks into various key issuesrelated to the management of degraded soilsfor increasing rice production on a sustainablebasis.

Alkali soilsAlkali soils also known as sodic or so­

lonetz soils have a pH of the saturation pastemore than 8.2, exchangeable sodium percent­age (ESP) more than 15 and soluble salts,mostly carbonates and bicarbonates of sodium.

capable of alkaline hydrolysis (Abrol et al,1980). The electrical conductivity of saturationextract (ECe) of the.;e soils is variable. Chemi­cal characteristics of a representative alluvialalkali soil are given in Table 2 (Bhumbla et al ,1973). The saturation extract though containsCI and 5°4 ions yet Na/CI+S04 is always morethan one. These soils contain 2 to 4 % amor­phous CaC03 in the surface and a hard pan,mainly dolomite, of variable thickness anddepth below the surface. The zone of calcichorizon possibly indicates the zone of shallowwater table fluctuations.

Table 2. Chemical characteristics of an alkali soil in the alluvial region -Kamal Haryana, India.

Depth, pHs ECe, CaCOJ , ESP Composition of saturation extract, me Llcm dSm I <2mm, 'X, Na Ca Mg K CO) HCOJ Cl S0.

o -10 10.6 22.3 5.1 96 248.3 0.7 0.2 0.4 141.6 136.2 6.6 3.910 -48 10.2 6.3 8.9 91 81.9 1.0 0.2 0.1 56.4 20.4 2.8 1.748 -76 9.8 4.2 9.4 88 49.1 0.7 0.2 0.1 26.8 19.6 0.8 1.176- 104 9.5 2.3 12.6 85 25.3 1.0 0.5 0.1 5.6 7.4 1.4 0.6104-163 9.6 1.3 13.8 69 12.3 1.0 0.5 0.1 3.8 7.8 0.3 0.5

Problems associated with these soilsfor raising rice crop are high pH, high ESP,high concentration of soluble C0

3, HC0

3and

low amounts of organic matter (O.M.). A com­bination of these factors leads to:

• Direct toxicity of excess Na.• Low concentration of soluble and

exchangeable Ca causing its nutritionaldeficiency.

• Deficiency of available micronutrients (Zn,Fe, Mn) due to their low solubility as aresult of high pH and immobilization dueto high concentration of C0

3and HC03 .

• Low efficiency of applied N due to highervolatilization losses.

• Antagonistic effect of high Na on Knutrition.

Poor physical conditions leading to lowinfiltration rate and poor air permeability, to­gether with a monsoon type of climate, makethese soils ideal for rice cultivation but unfit forraising other crops. Rice is the major crop withrice-wheat, rice-berseem (Trifoliumalexandrinum) , rice-mustard, rice-barley andrice-vegetables as important rotations.

Advantages of raising rice crop inalkali soils: Despite their low air and waterpermeability, alkali soils are suitable for grow­ing rice as the former do not adversely affectits yield. Further, rice is relatively tolerant to

6

5':>,III

"0

E 4u

~13

3IIIOJ

E"-OJQ."- 2.2::III

3

112 AGRICULTURAL REVIEWS

high amounts of exchangeable Na. up to ESP are highly suitable for low land rice yet to50, and hence can be raised even after adding achieve and sustain higher yields these soilslower doses of amendments. Rice once estab- face the following constraints:lished also helps in reclaiming alkali soils . . . . .(Chh I dAb I 1977) E t . f' Id t . Changes In SOli physIcal condItIOns:aora an ro . . x ensIVe Ie n- 1"als have shown that no other cereal crop can On. a~p !Cation of gyp:um ESP ~ec~eases,be raised under such adverse physical and whlc.h Improves the ?h~slca.1 propert1e~hke dls­chemical conditions of soils. In addition to the persIan and water mflltratlon rate (FIg. 1) ofgood quality groundwater available in these alkali soils (Chhabra, 1996). While in barrenareas, monsoon rains help in meeting to a sub- alkali soils the applied water stays on the sur­stantial degree, the irrigation needs of this crop. face for 3 to 7 days because of low permeabil­These soils have been reclaimed by applica- ity, it disappears within one or two days whention of amendments like gypsum and are be- these soils are reclaimed, adversely affectinging extensively cultivated for raising rice, wheat rice crop, which requires standing water for itsand a number of other crops. Approximately optimum growth. With time when them is a1. 1 million ha of such soils have been reclaimed decrease in soil pHI ESP of the surface as wellin the states of Haryana. Punjab and Uttar as of lower layers, there are serious losses ofPradesh and are contributing about 10 million applied water through deep percolation. Thustons of food grains annually to the national while in the initial few years there is .no needbasket. to puddle the soil, this practice becomes nec­Issues related to sustain rice yield in aIkali soils essary to cut down percolation losses during

Though alkali soils, on reclamation, rice cultivation in the reclaimed alkali soils.

\\,

\\\

\\\..."'-"

'''-.,.""......

I ! I I I ......-...1 1. I I

o 10 20 30 40 50 60 70 80 90 :00

Exchangeable sodium percentage

Fig. 1. Water permeability of an alkali soil as affected by exchangeable sodium percentage,

Vol. 23, No, 2, 2002 113

However, it should be clearly under- and Bhumbla, 1979) than other cereal cropsstood that despite improvements, reclaimed al- (Table 3, Chhabra, 1996) yet high pH (> 9.5)kali soils continue to differ from the normal and high ESP (>50) is detrimental to its opti­non-alkali soils of the area for a long time to mum growth, In these highly deteriorated soils,come, They continue to suffer from stagna- even for salt tolerant rice cultivars (Table 4),tion of water on irrigation or on heavy rainfall yield increases with an increase in applicationcausing short duration waterlogging for wheat of amendment (Mehta, 1996), though the sig­and other arable crops, The lower layers of nificant response is limited to gypsum levelthese soils get compacted due to clay move- equivalent to 50% of gypsum requirementment and pose resistance to root development (GR), Hence these soils must be chemicallyand water movement. ameliorated by application of amendments to

High pH/ESP leading to decrease bring ESP within the threshold value for grow­in yield: Though rice is relatively more toler- ing rice,ant (Fiq, 2) to soil exchangeable sodium (Abrol

8

.' • •• •

• • --.--------- . Rice" • ----. ---..........

6 • • -----...• •'~

•'co •.c

~ '\'s,c'iii •>-(J

4 "

\ •21 I I I I-'- ~

0 2C 4C 60 BO 100ESP

Fig, 2, Effect of ESP on yield of unhusked rice,

Grain yield of both rice and wheat sum, it gives higher yield than gypsum alonecrops increases with an increasing level of gyp- and hastens reclamation of soil (Swaroop andsum application from 0 to 5011\) GR (Table 5), Singh, 1993), Application of FYM as anWhile for rice gypsum application @ 25% GR amendment is ecorlOmical when it is availableis enough, for wheat increasing the amount to locally with the farmer and is free of cost., When50% GR is necessary to get optimum yields. it is·to be purchased then it is not economicalApplication of FYM @ 20 t ha-1 alone is infe- as compared to application of gypsum alone.rior to gypsum, but when combined with gyp-

114

TolerantESP, 35-50

AGRICULTURAL REVIEWS

Table 3. Relative tolerance of crops and grasses to soil ESP.

Moderately tolerantESP, 15-35

SensitiveESP. <15

Kamal grass (Leptochloa fusea)Rhodes grass (Chloris gayana)Para grass (Brachiaria mutica)Bermuda grass (Cynodon dactylon,Rice (OlJlza sativa)Dhaincha (Sesbania aculeata)Sugarbeet (Beta vulgarisjTeosinte (Euchlaena maxicana)

Wheat (Triticum aestivurri}Barley (Hordeum vulgare,Oat (Avena sativa)Shaftal (Trifolium resupinaturri}Lucerne (Medicago sativa)Turnip (Brassica rapa)Sunflower (Helianthus annusjSafflower (Carthamus tinctoiusjBerseem (Trifolium alexandrinum)Linseed (Unum siuqatissimuni)Onion (Allium cepa)Garlic (Allium sativum)Pearl millet (Penisetum typhoitesjCotton (Gossypium hirsutuni)

Gram (Cicer arietinuni)Mash (Phaseolus mungqChickpea (Cajanus cajan,Lentil (Lens eseulentliJSoybean (Glycine max)Groundnut (Arachis hypogaeliJSesamum (Sesamum orienta~

Mung (Phaseolus aureusjPea (Pisum saccharaturri}Cowpea ( lhgna unguiculata)Maize (Zea maysjCotton (Gossypium hirsutuni)

Table 4. Effect of graded levels of gypsum on the yield of rice (c.v. CSR-13)in an alkali soil of Uttar Pradesh, India.

Amount of gypsum added, Grain yield,thai °/" GR t ha- l

o7.515.030.045.0

o151530.3060.6090.90

o0.3901.1282.5522.603

Initial soil pH=10.32, GR= 49.5 t ha- '

Table 5. Effect of gypsum levels and FYM on the yield of rice and wheat in an alluvial alkali soil.

Treatments Grain yield, t ha- 1 After three years

1st year 2nd year 3rd year pH ESP

Rice Wheat Rice Wheat Rice Wheat

Control 2.98 0.20 4.55 1.00 20 1.20 9.5 55Gypsum @ 25 'X, GR 5.10 1.67 5.23 2.30 5.30 2.30 9.2 48Gypsum @ 50 % GR 5.44 1.99 5.46 2.30 5.30 2.40 9.1 42FYM @ 20 thai 4.05 1.42 5.20 2.00 5.30 2.20 9.3 56Gypsum @ 25 % GR + 5.78 2.14 5.76 2.80 5.80 2.80 9.1 38

FYM @ 20 thaiGypsum @ 50 % GR + 6.13 2.36 6.01 2.80 5.90 2.90 9.0 :F)

FYM @ 20 thaiLSD at P=005 0.33 0.35 0.41 0.36 0.40 0.34

Initial pH=10.4, ESP=89. Rice c.v. Jaya, Wheat c.v. HD 2009.

A package of practices consisting of old), incredsed application of fertilizer-N and aproper on farm development Le. bunding and proper dose of zinc sulphate have been evolved.land shaping, use of a higher number of seed- Following these practices it is possible to pro­lings per hill, closer plant spacing, use of older duce an average 6 tons of paddy and 4 tons ofseedlings (35 to 45 days instead of 21 days wheat hal in alluvial alkali soils (Fig. 3).

Vol. 23, No.2, 2002

Rice6-

III.c

:!i 5Q)

's.4t:

.~

c.J

115

2 4 6 8 10 12 14 16 IS 20Cropping years

Fig. 3. Grain yield of rice and wheat in fertilized plots ( N120 ,P22 , K50 .Zn5)in a gypsum amended alkali soil over a period of 20 years.

Evolution of high salt tolerant variet­ies (Mishra and Singh, 2000) like CSR 1, CSR2, CSR 3 CSR 10, CSR 13 and CSR 27, havemade it possible to get a moderate to goodcrop of rice with relatively less amount of gyp­sum application (up to 25 % GR). Ameliora­tion of alkali soils through the use of salt­tolerant rice varieties alone (without or withless amount of amendments), referred as bio­logical reclamation is another possibility for re­source constrained farmers. However, thismethod is slower and because of high soil pHIESP in the initial years promotes leaching lossesof phosphorus from the surface layers (Chhabraet aJ., 1981), higher volatilization losses of Nresulting in lower efficiency of applied fertiliz­ers (Bhardwaj and Abrol, 1978) and less avail­ability of applied Zn (Singh et al, 1987). Italso deprives the farmers from growing mod­erate and sensitive crops following rice, andthus is not economical over time.

Alkali soils once reclaimed do not pose

any repeated problem of high pH and ESP.(Chhabra and Thakur, 2000) for raising ricecrop. Surface application of amendments ac­companied by leaching, and continuous crop­ping with high water requiring crops keeps adownward flux of the replaced Na salts andwith time pushes these well below the activeroot zone. As a consequence of that pH of thesurface 15 soil stabilizes around 8.2 to 8.5 (Fig.4). During the initial years, only surface soil isreclaimed and depending upon the amount ofamendment added, leaching done and the in­ternal drainage, the lower layers take time toreclaim. But after 8 to 10 years. almost thewhole soil profile to a depth of one meter getsreclaimed and attains an ESP <15 (Fig. 5). Useof lower doses of gypsum than recommendedlevels, prolonged fallowing, change to low wa­ter requiring crops, flooding from the outsidearea, deterioration in groundwater quality be­ing used for irrigation and a rise in water tablecan result in a return of leached salts causing

116 AGRICULTURAL REVIEWS

resodication, These factors may necessitate a health (Chhabra and Kamra, 2000) for sus­repeat application of gypsum to restore soil taining crop yields,

9-5

9-0

8'5:r:0. 8<>'-

7'5

('0 -

1: L-lR 'II R W

2

L.-lH W

3R W

4

~k>-'C'I~

L..11 I I JJ I 1....JU--JRW RwRWRW~ 10 15 20

Years of cropping

Fig. 4. Changes in pH of surface 15 cm soil as affected by rice-wheat cropping sequencein a gypsum amended alkali soiL

ESP

0 20 40 60 80 100t I 1 I 1

•:. /15l-i .. /30~t .

E 45 i Iu

.c .I

15.60 \Cll

-0 •_. Original~

.. .\ I 0 o After 1 )'eOl

75 Xi K After 4 u. • ... After 8 II.1

..90l- \. .. _ .• AfterI5 tl

.I.

105 I- \\

.120

Fig. 5. Improvement in soil ESP over a period of time as a result of rice-wheat cropping in an alkali soiL

Vol. 23, No.2, 2002 117

Judicious use of irrigation water to arrest also higher cost of pumping from deeperdecline in water table depths. It is estimated that about 100 to 150

Rice is cultivated as low land paddy in .cm of irrigation water (depending upon the eco­alkali soils of north India. A major portion of logical zone) is required to raise a successfulirrigation is met through rainfall and rest is crop of rice. During initial periods of rainfall.supplemented by tube wells or canals. Sharma maximum amount of rainwater is either.used(1999) reported that due to over use of ground- for crop production or stored in soil while dur­water through tube w~lls, the water table in ing peak rainfall P2riod a substantial part ot itthese areas is falling continuously (Fig. 6). This is lost through deep percolation and/or throughhas led to low availability of groundwater and surface runoff.

Fig. 6. Rise and fall of water table, em/year, from 1974-94 in different districts of Haryana, India.

When one considers the water balance through groundwater (tube wells) o.r canal wa­(Fig. 7) during raising of a paddy crop in an ter. Since it is a large fraction of the totalalkali soil, in a state like Haryana, it is observed amount required and when tube well water isthat there is a serious deficit in rainfall in meet- the main source, it results in a big depletion ofing the water requirement of crop during early groundwater causing decline in water table ingrowth and near maturity. It is compensated most of the rice growing areas. As a re.sult of

118-... AGRICULTURAL REVIEWS

this, the fanners have to spend more money instead of continuous ponding as is thE! prac­to pump out water from deeper depths and tice in many states. Singandube (1986) showedalso risk the exposure- to the dangers of poi- that in alkali soils as much as 18 cm of irriga­sonous gases accumulated in the tube well pits tion water can be saved if it is given one day(Chhabra, 1988). To avoid such a situation, it after the disappearance of ponded water withis important that agronomic strategies must be out any significant loss in grain productionevolved to mJnimize the irrigation needs of rice (Table 6). A further saving of 35 cm water canand to conserve groundwater. Fewexperiments be achieved with only 13 % decrease in grainhave been conducted to see if irrigation water production. .can be saved by restonng to deficit irrigation

~~infQlf

0---0 Pohtl'ltiGI lIVOP-:ltronlfli:"Vtfllr.

•_. 4ctUof noporation

40.3836

[[I]JJ] SUrpllJS rainMlttr

r;:'; :. ,;] Vlflfer d.fieft

e:qz Sui' waTer lrtt'il!~i~"

3432

Tron*p:Qr.f

.~

30

90

Standard weeks

June July August September

Fig. 7. Water balance for rice duiing growing season in an alkali soil in Haryana, India.

Table 6. Effect of deficit irrigation on yield", water use efficiency and amount of water savedduring rice cultivation in an alkali soil in Haryana, India

Treatments Yield, t· ha·1 Amount ofGrain Straw water given,

em··

Water use Amount ofefficiency water

saved; cmContinuous submergence,S ±2cmIrrigation, 7 cm after 1 day of

disappearance of ponded waterIrrigation, 7 cm after 4 days of

disappearance of ponded waterLSD at P=0.05

4.70 6.254.52 5.85

4.26 5.34

0.27 0.56

10082

65

47.055.8

65.7

18

35

. "Mean of three years "" Includes rainfall Initial pH=9.3

Vol. 23, No.2, 2002 119

Sharma (2000) observed that 32.5 only saves the amount of water but also pre­and 46.3 cm of water, amounting to 40 and vents the deterioration of the soil which other­57% of the irrigation to be met from the wise will be adversely affected by higher use ofgroundwater or canal water, can be saved if such waters. Not only saving of water but theinstead of continuous ponding, water is applied grain yield and water use efficiency was alsoafter 3 and 6 days of disappearance of the more when irrigation was applied after 3 daysponded water, respectively to a rice (c.v. Jaya) of disappearance of ponded water instead ofcrop raised in an area with problem of RSC continuous ponding.(Table 7). In such areas deficit irrigation not

Table 7. Effect of deficit irrigation on yield', water use efficiencyand amount of water savedduring rice cultivation under sadic ~ter conditions.

Grain yield, Am unt of Water use Amount oft ha·1 water g'iven, cm" efficiency water saved, cm

2.97 da.l 22.313.73 100.6 37.08

Treatments

Continuous submergence, 5± 2cmIrrigation, 6.5 cm after 3 day of

disappearance of pond~ waterIrrigation, 6.5 cm after 6 days of

disappearance of ponded waterLSD at P=0.05

3.17

0.29

86.8 36.52

32.5

46.3

'Average of two years."Quality olirrigation water used: EC1.7-1.9 dSm-l, RSC 7.5-8.6 meL-I, SAR 9.2-11.5."'Includes rainfall of 51.75 cm.

. Irrig'ation should be so planned as toavoid water stress in rice during its reproduc­tivegrowth phase. It is most crucial stage aswater stress during this period leads to higherpercent~ge of sterility and thus decreases thenumber of filled spikelets. There is however,no effect on 1000 grain weight. Adverse ef­fects of water deficiency on growth of rice inearly stages is observed to decrease plantheight, number of tillers, total functional leaves,leaf area and the accumulation of dry weight.This decrease in agronomic attributes mayormay. not affect the grain yield, if water is ap­plied in good quantities for recovery of plantsbefore flowering.

Management of rainwater to rechargegroundwater .

The storage of rainwater in rice fieldsenhances its utilization in crop production,.avoids moisture stress during. dry' spells andminimizes irrigation water requirement andinduces groundwater recharge. The amount of

storage depends upon the quantum of rainfalland its distribution, height of dikes around ricefields, and the soil and varietal characteristics.The dike height should be so planned that itstores' maximum amount of rainwater in thefield. h has been observed that rainwater up to15 cm storms can be safely stored in bundedrice fields. Recharge of groundwater throughrainwater retained in the existing paddy fields.so as to allow it to seep through the soil is anatural, viable and practical solution.

. The excess wat~r after storage in therice fields should be stored in the dug-out pondslocated in the lower regions of the farm. Thiswater is to be recycled for irrigation during dryspells. It can also be used to artificially rechargethe depleted aquifers through specially createdbore filters to arrest declining water table leveland to improve its quality in areas dominatedby groundwater irrigated rice. It has been ob­served thatby adopting these strategies 80 to90 per cent of the rainfall can be utilized within .

Change in date of transplanting:Due to high temperature and low relative hu­midity before the onset of monsoon, there is amaximum loss of applied water through evapo­transpiration in the months of May and June.

. As a consequence of this, early transplantingof rice Le. before first week of June leads tohigher losses of applied water. A study con­ducted in the Punjab (Anonymous, 1995)showed that there is no decrease in yield ofrice when transplanting is completed up to June(Table 8). Hence the farmers should not go infor an early transplanting of rice so as to con­serve groundwater.

Contrary to this, there is a practice inthe states of Punjab and Haryana to raise anadditional crop of rice, commonly known asSathi rice (c.v. Govinda is mostly used for thispurpose) during this period. Also known as Mayplanting of rice or summer rice, it is most un­sustainable, as it demands pumping of large

120

the farm area.

AGRICULTURAL REVIEWS

quantities of underground water which may fur­ther worsen the water table in northern states.This practice not only promotes wastage ofirrigation water but also the quality of rice raisedduring this period of high temp~rature and highhumidity at the maturing time is poor. Suchrice has low storage quality and gets higherpercentage of brokens during' mming, and dueto these reasons it fetches low price in themarket. Practice of raising summer rice mustbe curbed by either levying additional electric­ity charges for tube wells or stopping the sup­ply of canal water during this period so as tosave water. During th+s period the farmersshould be advised to take a pulse crop like greengram or cowpea at least. on non-alkali and re­claimed alkali soils. Such crops demand lesswater during summer months and contributeto soil fertility by addition of organic matterand fixation of atmospheric nitrogen. Raisingof Sesbania as a green manure crop for themain season rice crop is the best solution.

Table 8. Yield of rice as affected by the date of transplanting in Punjab, India.

Transplanting period Yield, t ha· 1

1991-92 1992-93 1993-94 Mean

Up to 15 th May 3.40 3.50 3.70 3.53• 16 - 31 May 3.35 3.56 3.72 3.54

1 - 15 June 3.43 3.56 3.76 3.5816 - 30 June 3.29 3.43 3.51 3.41

1 - 15 ,July 3.00 2.85 3.03 2.9616 - 31 July 2.43 2.65 2.55 2.54After 31 July 196 2.59 2.22 2.26

Deterioration in groundwater quality·There is more percolation from low

land rice fields as compared to from the fieldssupporting upland crops. Percolating waterfrom surface layers increases the salt load ofgroundwater and deteriorates its quality. Otherreasons for deterioration of groundwater qual­ity under rice cultivation are:

• less recharge of groundwater as comparedto.,its depletion.

• contamination with salts which were earlier

distributed uniformly through out the soilprofile,

• lowering of the water table exposing it tothe saline aqUifers, and

• leaching of N03 and pesticides applied torice fields.

Mehta and Singh (1989) observed thatafter 15 years of reclamation, groundwaters indistrict of Kaithal, Haryana, India became moresaline (Table 9). Over time, not only were theirsalt roads as measured by EC but also their

VoL 23, No.2, 2002 121

sodicity hazards in term of residual sodium car- tion, deterioration in its quality may be the causebonate (RSC), sodium adsorption ratio (SAR) of resodification of the surface soil necessitat­and soluble sodium percentage (SSP) increased ing repeat application of gypsum in these ar­significantly. Since this water is used for irriga,-'·eas.

Table 9. Changes in groundwater quality after reclamation in Kaithal area of Haryana, India.

Constituent Before reclamation After 15 years of reclamation

Ca, meL!MgmeLlNa meL!KmeL!C0

1meL!

HCO"meLlClmeLlSO. meLlEC, dSm·1

RSCmeLlSAR, (mmol-') ·112

SSP

1.153.454.180.102.904.451.251.080.691.952.75

45.80

1.634.005.680.271.236731.980.901.063.652.85

48.25

Table 10. Groundwater quality as affected by depth in village Golewala, Faridkot district of Punjab, India.

Water table depth, m EC, dSm 1 RSC, meL'l Quality rating

3.0 - 10.5 0.43 - 0.45 -0.1 -0.8 Fit for irrigation10.5 - 12;0 0.45·0.60 0.8'· 3.8 Marginal12.0 - 15.0 0.60 - 1.77 3.8 -12.1 Unlit>15.0 1.77 - 2.32 12.. 1-16.3 Unfit

In arid areas there is generally dete- increased, mainly due to the contributions ofrioration in groundwater quality with depth. But excessive salts from the soil profile. These in­in such areas when canal irrigation is intro-vestigations point·· out that there is a seriousduced, the quality of water at shallow depth~. risk of groundw,atet quality deteriorating on in­improves due to continuous seepage from toe· i

troductionqf.canal irrigation in riye growingdistribution system. Hira and Murty (1985k~ areas, the degree being more in zones alreadya case study conducted in Golewala villag~'ln having brackish water. Further, as a CQnse­Faridkot district of Punjab found that a thin quent~ of easy availability of canal water, thelayer of fresh water floats over the saline water f.P.r..mers do not use underground brackish wa­in most of the canal command areas (Table tel"' resulting in rise in water table and ultimately10) and is used for irrigation. But as the water formation of waterlogged saline soils.table declines, due to over exploitation, thlt Decrease in soil fertilitygroundwater quality deteriorates increasing the Salt-affected soils are poor in a.M. andrisk of salinization of soil. available N. In the initial years due to high pH,

Wheni! groundwaters are already sa- ESP and high a,mounts of CaC03 , about 32 toline like that in R"ohtak, Bhiwani, Hisar, Sonepat 50 lXl of the applied N-fertilizer is lost throughand Jind districts of Haryana, India, seepage volatilization (Bhardwaj and Abrol, 1978) re­from the canal irrigation system have not shown suiting in lower efficiency Of applied chemicalany improvement in their quality. On the con- fertilizer. Along with this due to low symbiotictrary, inmost cases the groundwater salinity fixation of atmospheric N and low activity of

122 AGRICULTURAL REVIEWS

soil microorganisms, the contribution of N for Ca(HpO4)2' higher fixation of soluble P by soilplant need from these sources is very low. As due to decrease in pH and depletion as a resulta result of this N needs of alkali soils for crop of plant uptake. Hence on reclamation avail­production are relatively higher as compared 'able P of the surface soil decreases below theto that of normal soils. Since these soils con- critical level which results in low yields espe­tain less amount of O.M. and it is not possible .'cially of rice crop which depends on the fertil­to build inorganic-N reserves in the soils; it is ity of the surface soil. However, with time evennecessary to apply appropriate amount of N- the yields of w~ crop start declining in Pfertilizers (120 - 150 kg N ha-1) to sustain rice control plots-}ig. 9}. From a long term fieldproduction even after reclamation of theSe soils. study, Orflabra and t~ur (2000) suggested

Though all alkali soils under natural to aW1y 22 kg P ha-1 aftet three to five yearsconditions are calcareous and contain appre- of fe~lama~o~ to b~th rice.an~ wheat crops tociable quantity of CaC0

3yet due to its low sustaIn their YIelds In alkah s01ls.

solubility at high pH, the crop suffers from its Alkali soils also contain high amountsdeficiency. Lack of Ca also results in disturbed of extractable potassium and do not respondCa, Na and K ratio causing excess of Na and to application of potassic fertilizers. But withaffecting yield. In the-initial years of reclama- time there is high removal of exchangeable Ktion, application of amendments like gypsum as well as the one released due to solubility ofhelp in lowering pH, ESP and meeting the Ca cl(\,Y minerals (Pal and Mondal, 1980). ~s aneeds of plants. During next phase, Ca needs re!Llt of this though the rice crop does not suf­of the plants are met through solublization of fer due to K deficiency in the initial years, itsnative CaC03 through the action of roots, Ca level may become critical if farmers do not prac­contained in the irrigation water and that sup- tice balanced use of fertilizers. Rice crop raisedplied through the chemical fertilizers like single in high ESP soil, shows high Na-K ratio thatsuper phosphate and calcium ammonium ni- may prompt application of potassic fertilizers.trate (Chhabra and Kamra, 2000). Due to these But the remedy lies in correcting Ca-Na-K bal­reasons rice plants grown in reclaimed alkali ance by judicious application of amendmentssoils seldomsuffer from Ca deficiency: (Chhabra and Abrol, 1983) rather than apply-

Alkali soils though deficient in a.M. in~ potassic fertiliz~rs to a.lready K.rich alkaliand available N, are rich in extractable phos- ~011~: Among the mlcro~utnents, ~n IS th~ m~stphorus. This is mainly due t~he fact that hm~tI~g fo~/growth of nce c.rop In alkah s01ls.Na CO and NaHCO present in these soils ThiS IS maInly as a result of ItS decreased solu­rea~t with native apatite to form soluble so- bility due tq hig~ ~~, CaC03, and soluble. phos­dium phosphate. Trivalent phosphate ions of ph~tes: In the Initial stages o~ re~lamatlon al­this are converted into H PO ions when these kah s01ls n~ a r~gular fipphcatlon of 10 tocome in contact with the piant roots in the 20 kg zinc stJ.lphate ha-1

whe~ opti~um d~serhizosphere and thus meet the P needs of the of gypsum a~ an .amendment IS apphed. ~Ithcrop. Due to high amounts of extractable P in passage of tIme, the ~eed for supple~en~Ingthese soils, rice and wheat grown in the first Zn can be reduced With out any loss In YIeldfew years do not respond to application of (Chhabra et al., 1982).phosphatic fertilizers (Chhabra, 1985). Butwith Post reclamation management of nu­time, the soluble P decreases (Fig. 8) due to trients in alkali soils is very crucial to maintainleaching from the surface to the lower layers, their fertility for sustaining rice production.conversion of Na

3PO4 into less soluble Along with application of chemic~1 fertilizers,

O,"-..I-....1.-..L-..J--J--J--.L.....J.--I_L-1.--lRW~WRWRW~WRW

I 2! 4 5 eCropping year

'Fig. 8. Changes in Olsen's extractable P as affected by reclamation and application of P and Kin an alkali soil fol1owing rice (R) - wheat (W) cropping sequence.

o X

CIl 10%e

20"E0u·

0...5

~ 30 X

~40X

.. .. .. .. Rice:p ..u • .. •;:l •""Cll..c§!.

I2 4 6 8 10 12 14 16 IS" 20

Nos. of cropping yearsFig. 9. Relative response of rice and wheat crops to P application as per cent reduction in yield in P control

plots over those receiving 22 kg P ha· l in a gypsum amended alkali soil over a period of 20 years.

124 AGRICULTURAL REVIEWS

proper maintenance of O.M. through the useof green manuring, FYM, compost, poultrymanuure and recycling of~rop residues in thesesoils is crucial for obtaining higher efficiencyof inorganic fertilizers, to maintain good physi­cal properties and to improve their biologicalhealth.

Saline soilsSaline soils have excess soluble sqJ{s,

mostly ECe >4 dSml, pHs <8.2 and ESP <15.In areas affected by primary salinity Le. wheresalt accumulation is due to lack of leaching ofweathering products, rice is not grown. But inareas suffering due to secondary salinisationi. e. salinity developed due to rise in water tableas a result of introduction of canal irrigation,rice is being grown as a major crop. This ismainly due to compulsion of using these wa­terlogged soils, as no other crop will grow un­der such situations. As per the estimates ofMinistry of Water Resources (Anonymous,1991) an area of 2.46 million ha has becomewaterlogged in various major irrigation com­mands in India alone. Such areas are increas­ing at an alarming rate due to non-judicioususe of canal irrigation in otherwise dry landareas.

Rice crop raised under saline environ-ment suffers due to the following problems:

• Osmotic stress due to high soluble salts.• Toxic effects due to high concentration 6f. CI and S04'

• Fluctuating water table.• Water stress near maturity leading to

sterility.

In areas, where with the provision ofdrainage facilities, water table can be loweredand salinit'I,: managed, rice crop should neverbe grown. Where groundwater is saline andshallow and there is no drainage, rice with salttolerant varieties is the only choice. This hasto be managed as mono-cropped area. Thesesoils have low to medium.fertility status andneed a regular application of balanced fertil-

izer on soil test basis to obtain and sustain op­timum yields.

Since these soils have shallow watertable which fluctuates between surface undula­tion at the time of rice transplanting to 2 metersbelowft\e surface at the time of maturing, va­ri~s adaptable to such fluctuating water tableshould be evOlved. These varieties should alsobe more tolerant to toxic concentration of ele­ments like F, Se, Mo and B present in thesesoils and high levels of salinity at the time ofmaturity.

Deterioration in soil properties due to useof brackish groundwater

large parts of Haryana, Punjab andUttar Pradesh in India and in many other coun­tries have a problem of brackish undergroundwaters. These waters have low salt concentra­tion (EC 1. 7 to 1.9 dSml) but high RSC (7.5to 8.6 mel'l) and high SAR [9.2 to 11.50(mmoleL-I)'1/2). Some times these waters alsocontain high amounts of toxic elements like F,B, Si, Se an.d Mo. These elements are less toxicto rice plant but may be-harmful to the animalsthat feed on straw of crops raised with suchwaters (Singh et aI, 1979). Soil crust formeddue to use of RSC waters leads to low germi­nation and poor stand of upland crops. lowinfiltration rate causes stagnation of rainwaterduring monsoon and leads to failure of manyarable crops. Due to these reasons the farm­ers are resorting to cultivation of rice as a ma­jor crop in these areas.

Most of RSC waters found in Punjabhave low EC and low Ca content «2 meL-I).Such waters are more harmful as these causesoil deterioration much faster, lead to rise inSAR quickly and pose problems of soil perme­ability (especially during rainy season) due tolow electrolyte concentration. While most ofthe RSC waters found in Haryana have rela­tively high EC and soluble Ca (>2 meL-I). Suchwaters are less harmful as their high Ca con­tent together with high amount of CaC03 found

Use of such waters leads to rise in pH,ESP, deterioration of physical and chemicalproperties of soils, After a continuous and pro­longed use of such waters, the upper soil lay­ers also show increase in EC affecting the yieldof crops following rice, These soils are thenlabelled as saline-alkali soils,

To sustain rice yields and to preventthe failure of other crops following rice, it isrecommended to treat irrigation water to neu­tralize its RSC so as to bring it within the' safe:tin ±.of2 5 meL!, Soils, which due to the useof high RSC waters have developed high pHand ESP should be treated as alkali soils andreclaimed through the use of gypsum as dis­cussed earlier. "

CONCLUSIONSFrom the foregoing discussions,it is

evident that to sustain rice production in de­graded soils like alkali and saline soils, to main­tain their productivity and groundwater balance,the following points should be considered:

• Ban cultivation of summer rice to avoidthe period of maximum evaporation andto conserve groundwater for the main sea­son crop, Raising a pulse crop like, greengram or cowpea at least on reclaimed al~

kali and non-alkali soils during this periodwill lower the water demand and improve

Vol. 23, No.2, 2002 125

in these soils and the monsoon type of cli- soil fertility, Sesbania should be raised asmatic conditions of the area causes less dete- agreen manure crop for the main seasonrioration in soil. rice crop dUring this period.

• Encourage farmers to transplant paddylate, i.e. by the end of June, to avoid theperiod of maximum evapotranspirationand hence reduce the demand on ground­water,

• Shift from conventional ponding/submer­gence to irrigation for maintaining soilsaturation so as to save water in decliningwater table areas.

• Decrease the area under rice and producemore from the existing area, Diversify thecropping pattern to horticulture,olericulture and floriculture on those re­claimed alkali soils that have a good watersupply.

• Recharge groundwater through rainwaterto maintain water balance and to preventdegradation of its quality,

• Gypsum treated RSC water should be usedfor"irrigation to minimise their deleteriouseffects on soil physical and chemical prop­erties,

• Maintain optimum soil fertility throughbalanced and integrated nutrient manage­ment.

• Develop varieties suitable for saline soilswith fluctuating water levels, tolerant totoxic levels of Fe, S and high levels of sa­linity at maturity.

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Report of the Working Group. Ministry of Water ~esources, Govt. of India. New Delhi.Anonymous. (1995). Agricult~ral Statistics of Punjab. Dept. pf Agriculture, Punjab. 62 p.Bhardwaj, K. K. R. and Abrol, I. P. (1978). In: Proc. Nat. Syf1p. Nitrogen Assimilation and Crop Productivfty. Hisar,

India. pp. 83-96.Bhumbla, D.R. et al. (1973). Bulletin No. 1. Central Soil Salrity Research Institute, Kamal. India. pp. 43.Chhabra, R. (1985). Agron. J 77:699-702.Chhabra, R. (1988) Indian Fmg. 38 (6):39-43. .Chhabra. R. (1996). Soil Salinity and Irrigation Water Q\.I':llity. Center for Irrigation Engineering, KUL, Belgium.

Oxford and IBH Publications, New Delhi, India. 284 p.

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Chhabra, Rand Abrol. I.P. (1977). Soil Sci. 124:49-55.Chhabra, Rand Abrol. I.P. (1983). Ferti/. Industry Ann. Rev. India. 11:147-159.Chhabra, R. etal. (1981). Soil Sci. 132:319-324.Chhabra, Rand Kamra, SK (2000). In: Int. Conf. Mgmt. of Natural Resources for Sustainable I'lOduction in the

21" Century. New Delhi. 1:47-49.Chhabra, R. and Thakur, N.P. l2000). .Rice-Wheat Consortium Paper Series 6, New Delhi, India. pp. 31-39.Chhabra,it "Naf\19B"Z)'-{n: Annual Report. Central Soil Salinity Research Institute. Kamal', India. pp.4.Dudal. Rand Pumell. M.F. (1986). Reel. Revegetation Res. 5: 1-9.FAD (1998). FAG Yearbook Production. Rome. 51. 241 p.Hira. G.S. and Murty. V.V.N. (1985). An appraisal of waterlogging and drainage problems in South-West part of

Punjab. Department of Soil and Water Engineering, Punjab ASricultural University, Ludhiana. India. pp.1-45.Massoud, EI. (1974). Salinity and Alkalinity as Soil Degradation Hazards. FAG-Unesco Publication. Rome. 74: 10.Mehta, KK (1996). In: Annual Report. Central Soil Salinity Research Institute, Kamal, India. pp.45.Mehta. KK and Singh, N.T. (1989). In: Annual Report. Central Soil Salinity Research Institute, Kamal, India. pp. 24-26.Mishra, B. and Singh, RK (2000). In: Research Highlights in Indian Agriculture (in Hindi). Central Soil Salinity

Research Institute, Kamal, India.pp.165-169.Pal, OK and Mondal, R.c. (1980). J Indian Soc. Soil Sc. 28:347-354.Sharma, OK (2000). In: Rese~rch Highlights in Indian Agriculture (in Hindi). Central Soil Salinity Research Institute,

Kamal, India.pp.38-42. .Sharma, RC. (1999). Lecture - Note. In: Sensitizato.n Workshop on Sub-surface Drainage for Reclamation of Water-

logged Salt affected Soils. (Unpublished) Central Soil Salinity Research Institute, Kamal, India.Singandhube, R.B. (1986). Ph.D.Thesis. Central Soil Salinity Research Institute. Kamal, India. 230 p.Singh, A. etal (1979). Soil Sci. 127: 86-93.Singh, MV. eta/. (1987). J Agric. Sci. (Camb.). 106: 275-279.Singh, N.T. (1992). In: Land and Soil. (Khoshoo, T.~. and Deekshatl{lu, B.L ed.). Har-Anand Publications,

New Delhi, India. pp. 65-100. .Swaroop, A. and Singh, KN. (1993). In: Annual Report. Central Soil Salinity Research Institute, Kamal, India. pp. 31-32.