Saline water management for irrigation in India

Agricultural water management ELSEVIER

Agricultural Water Management 30 (1996) l-24

Review

Saline water management for irrigation in India P.S. Minhas Central Soil Salinity Research Institute, Karma1 132001, India

Accepted 3 August 1995

Abstract Much (32-84%) of the ground water surveyed in different Indian States is rated either saline or alkali. Because of the continental monsoonal climate, the basic principles of saline water management need some adaptation, e.g. providing for a leaching requirement is not appropriate when the growing season for post-monsoon winter crops starts with a surface-leached soil profile, because it would increase the salt load. High salinities during the initial stages of growth are particularly harmful. Further, if benefits are to be gained from frequent saline irrigation, the amount of water applied per irrigation needs to be reduced. This is not possible with most widely practiced surface irrigation methods, but can be achieved with sprinkler and drip methods. However, in India the large-scale use of such systems is not yet technically or economically feasible. Another management goal is simultaneously to encourage the utilisation of carried over rainwater in the soil profile/shallow watertables. Tolerance limits of crops to the use of saline water in different agro-ecological regions of India are available, and have been observed to vary with soil type, rainfall and anionic/cationic constituents of salinity. Multi-location trials on the appropriate use of saline and non-saline water reveal the benefits of irrigating with non-saline canal water during the initial stages of growth, as well as cycles of saline and non-saline water during the pre-sowing irrigation period. Monsoon-induced salt leaching decreases with increasing clay content, SARi,, and is enhanced with increasing chloride salinity. Additional doses of phosphorous to alleviate the effects of chloride toxicity, and the use of organic materials to enhance the efficiency of applied nitrogen are recommended under saline-irrigated conditions. Contrary to the general belief that soils irrigated with high-SAR saline water may regain their infiltration capacity when the electrolytic concentration of ingoing water is greater than the flocculation value, irreversible reductions are induced under cyclic saline-rainwater infiltration where sub-soil layers, ingressed with clays from the plough layer, control steady intake rates. Thus, the use of gypsum (SARi, > 20) is advocated. Gypsum is also needed for soils irrigated with saline water with an Mg:Ca ratio > 3 and rich in silica. Other cultural practices, such as furrow planting, increasing the plant density and post-seeding irrigation in crops like mustard, also prove useful. Water-quality standards which were too conservative have been replaced by site-specific guidelines where factors such as soil texture, rainfall and crop tolerance have been given due consideration. 0378-3774/96/$15.00

0 1996 Elsevier Science B.V. All rights reserved

SSDI 0378.3774(95)01211-7

P.S. Minhus/Agriculturul

2

Wuier Management 30 (1996) l-24

1. Introduction The concerns about the utilisation of poor-quality underground water, which occurs worldwide and especially in arid and semiarid areas, are not new. With scientific advances, the basic principles of soil-water-plant systems, as described in several reviews (Shainberg and Shalhevet, 1984; Ayers and Westcot, 1985; Tanji, 1990; Rhoades et al., 1992) are now well understood. Nevertheless, the modifying influence of monsoonal rains upon salt dynamics in soils, and consequently on crop growth, means that working principles for the effective use of saline water resources under the continental monsoonal climate of India require some adaptation. Poor-quality irrigation water constitutes 32-84% of well water surveyed in different Indian States and, based upon their characteristic features and specific management practices, are broadly grouped into two categories, i.e. saline water (with excess salts) and alkali water (with residual alkalinity). This paper is concerned only with the agro-management strategies emerging from research into saline water during the past two to three decades. The objectives of management practices to be followed for optimal crop production with saline water include the prevention of salt build-up to levels which limit the productivity of soils and the control of salt balances in the soil-water system, as well as minimising the damaging effects of salinity on crop growth (Meiri and Plaut, 1985). Amongst the various water, crop and soil management options available, there is no single measure which will control the salinity of irrigated soils; several practices interact with each other, and should be considered in an integrated manner, along with climatic and human factors. However, for a better understanding of the subject, each management option is discussed separately.

2. Water management 2.1. Leaching

management

One of the advantages of a continental monsoon climate is the concentration of rains in the short span of 2-3 months (July-September). Thus, if water penetrating into the soil during this period exceeds the evapo-transpiration (ET) demands of the crop, it induces leaching of salts added through saline irrigation of winter crops (Gupta and Abhichandani, 1970; Pal and Tripathi, 1979; Manchanda and Chawla, 1981; AICRP, 1994), or in low-rainfall regions farmers resort to fallows during monsoon rain to achieve the necessary salt balance (Dhir, 1977). As well as the amount and frequency of rains during the monsoon season, salt leaching is also governed by soil texture. This is clear from the following hyperbolic relations developed by Minhas and Gupta (1992) from a number of experiments conducted over varying rainfall and soil conditions. Fine-textured soils (clay loam, silty clay loam), ECJEC, Medium-textured ECJEC,

= 0.1916( D,/D,,)

+ 0.0962

r = 0.75

soils (sandy loam, loam), = 0.1919( DJD,,)

- 0.0017

r = 0.95

P.S. Minhas/Agricultural

Coarse-textured ECJEC,

soils (loamy

Water Munagement 30 (1996) 1-24

3

sand, sand),

= 0.1577( DJD,,)

- 0.0068

r = 0.66

where EC, and EC, denote the electrical conductivity of a saturation paste extract of the soil (dS m- ’) after and before the monsoon. D, and Drw represent the depth of the soil and depth of rainfall received during monsoon, respectively. From the above relations, it can be calculated that removal of 80% of the salts accumulated during the period preceding monsoons would require 1.85 cm, 0.95 cm and 0.76 cm of rainwater per centimetre of soil depth in fine-, medium- and coarse-textured soils, respectively. Obviously, the lower water-holding capacity of coarser soils leads to higher pore volumes of displacing solutions consequent upon similar rainfall. A larger fraction of rainwater also tends either to run off or to evaporate from stagnant water on the surface of the soil due to the low infiltration rates of fine-textured soils (having a high clay content), and this reduces the water available to displace the salts. Leaching of salts during monsoons has also been observed to be affected by the anionic constituents of saline irrigation water. In a sandy loam soil irrigated with saline water (EC, 16 dS m-l), higher salt leaching with monsoon rains was observed when irrigation water had a predominance of chlorides rather than sulphate ions (Chauhan et al., 1991; Singh et al., 1994). The amounts of rainwater needed to leach out 80% of salts were 0.60 cm, 0.89 cm and 0.92 cm per centimetre depth in soils irrigated with water having Cl:SO, ratios of 3: 1, 1:l and 1:3, respectively. Whereas the soil profile was almost free from Clbecause highly soluble salts are leached easily, some SOiwas retained because precipitated sulphate salts in the soil (e.g. relatively insoluble gypsum) continued to dissolve with the passage of each influx of rainwater. Studies on the leaching behaviour of high SAR-saline/sodic water irrigated soils (Sharma and Khosla, 1984; Singh et al., 1992) have shown that during leaching, especially when low electrolytic water infiltrates the soil (Minhas and Sharma, 19891, pH increases and soil clays become vulnerable to dispersion and movement. Thus, salts are held back, and such soils require almost double the quantity of water (Table 1) than leaching of waterlogged saline soils (Laffelaar and Sharma, 1977; Khosla et al., 1979). As a consequence of this, more salts are retained in soils irrigated with water of the same salinity but higher SAR (Dhanker et

Table 1 Comparative

leaching

Water/Soils

*

EC

RX

SAR

Saline soil 63.8 123 Soils irrigated 2.6 20.5 12 5.0 12 20.0 12 40.0

curves for water-logged Leaching

saline and saline water irriagted

curve

C/Co = 0.864 exp.( - 3.646 Dw/Ds) with saline waters 9.5 C/Co = 0.163 (Dw/Ds)-‘.~‘* C/Co = 0.1440 Ds/Dw + 0.0296 C/Co = 0.2276 Ds/Dw - 0.027 1 C/Co = 0.15 10 Ds/Dw + 0.0079

soils

Dw/Ds for 80% salt removal

Reference

0.4

Khosla et al. (1979)

0.9 0.8 1.o 1.3

Sharma and Khosla (1984) Singh et al. (1992)

C and Co represent salt remaining and initial salts. Dw and Ds represent respectively. * Analysis is for saturation paste extract in saline soil.

depth of water (cm) and soil,

4

P.S. Minhas/Agricultural

Water Management 30 (1996) I-24

al., 1986; Singh et al., 1992). Addition of gypsum enhance infiltrability is advocated for such situations. 2.2. Leaching

to prevent

surface

sealing

and

requirement for salt balances

The traditional salinity management approach (US Salinity Laboratory, 1954) assumed the steady-state conditions to exist in the long run, which implied that the economic way to control soil salinity was to ensure net downward flow of water through the root zone. Therefore, the leaching requirement was defined as the minimal fraction of the total water applied that must pass through the root zone to prevent reductions in crop yield below the acceptable level. The leaching requirements for any acceptable yield (Y,) can be calculated using the equations RY = Y./Y,,,

= 1 -S(EC,-EC,)

EC, = EC, + ( 1 - K/Y,,,,, )/S) LR = EC,,/EC,, For LF > 0.3, EC, = EC,,/2.5

or LR = ECi,/2.5

EC,

where EC, is the threshold salinity, and EC,, and EC,, are the irrigation and drainage water salinity respectively. The concept of leaching requirement is mainly of practical importance for situations of very low rains or none at all, where the steady state can very nearly be achieved. However, under a continental monsoonal climate such as in India, the concentration of rains in the short time of 2-3 months is the least controllable factor causing non-steadystate salinity. It leaches down the salts when infiltrating down into the soil, and gets stored in the soil profile to be held until either it gets mixed with the saline irrigation water or consumed by winter crops. A large number of experiments (AICRP, 1994) have shown that the practices of providing leaching requirements to crops do not have much benefit (Table 2). Recent simulation studies by Minhas and Gupta (1993a) have shown that any practice that requires a quantity of applied water in excess of the irrigation Table 2 Yields of wheat and barley as affected by leaching Diw/ CPE

1.0 1.25 1.5 1.0 1.25 1.5 1.0 1.15

Grain yields at ECiw (dS mBAW

4

8

AGRA (Bajra-wheat, 6y) 43.3 42.7 40.7 46.1 44.5 44.0 46.6 45.8 46.6 HISAR (Bajra-wheat, 7~) _ 38.3 41.3 42.0 45.5 _ 43.1 45.8 JOBNER (Fallow-wheat, 6~) 24.1 22.7 23.7 25.8 26.6 25.5

fractions

at different

salinities of irrigation

waters

I) 12 36.2 39.3 40.4 _ _ _ 22.3 22.6

BAW

4

8

Dharwad (Sorghum-wheat, 6y) 27.3 27.32 32.7 35.3 31.5 30.0 33.5 26.6 29.3 HISAR (Fallow-wheat, 3~) 60.2 60.5 56.2 63.9 62.9 59.0 58.3 62.8 65.7 JOBNER (Fallow-barley, 4y) 50.8 42.3 44.4 44.4 41.1 47.7

12 24.7 28.9 24.7 40.7 42.4 44.8 43.1 41.0

Diw-depth of irrigation water (cm) was 5.0, 6.25 and 7.5 cm, respectively for Diw/CPE of 1.O, 1.25 and 1.5. CPE denotes cumulative pan evaporation at which irrigation was applied (5 cm). BAW is best available/canal water.

5

P.S. Minhas / Agricultural Water Management 30 (1996) I-24

.L

I

No. of irrigations

ECiw (dS/m)

I.0 -

??

4

0.6

6 .

5

0 4.0

0.4

02

0.6

DiwKPE

ratio

0.8 for irrigation

1.2

1.4

1.6

(75mm)

Fig. 1. Simulated wheat yields as affected by different quantities and qualities of irrigation water. Di, and CPE denote depth of irrigation water (75 mm) and cummulative open-pan evaporation between two irrigations.

needs of the crops pushes the stored good-quality rainwater, which otherwise would have been used by the crops, down below the rootzone. Therefore, there are very few advantages in applying extra saline water to meet leaching requirements (Fig. 1). Moreover, it has been observed that although equal salt inputs, which increased salinisation rates during the later stages of growth, resulted in higher salinity of the surface 0.3 m of soil, they were less toxic and produced almost 1.8 times the wheat yields (Fig. 2) of the higher salinisation rates but with lower final salinities (Minhas and Gupta, 1993a). 20

l5-

0

EC iw

Gminyield(g/lysi)

0

Constant

42.4

0

Increasing

69.5

X *

Decreasing SW after

46.9

20

40

60

I 60

I too

I 120

I 140

Time after sowing (days)

Fig. 2. Salinity build-up and wheat yields with application of water of constant (SW:NSW 3:7 throughout), increasing (SW:NSW 1:9, 2:8, 3:7, 46, 5:5) and decreasing EC,, and when SW was introduced at tillering (SW:NSW 0:l. 0~1, 2.5:7.5, 6.25:3.75, 6.25:3.75), but with similar total salt input. SW = 400 me I-’ (EC, 34.2dSm-‘),NSW=0.4dSm-‘.

P.S. Minhns/Agricultural

6

3. Farm irrigation 3.1. Irrigation

Water Management 30 (1996) 1-24

management

interval

Under saline conditions, irrigation should meet both the water requirements of crops and the leaching requirements to maintain a favourable salt balance in the root zone. During the intervening periods between irrigation cycles, ET by crops reduces the soil water contents, which in turn deceases the matric as well as solute potentials. The rate of ET and the soil water characteristic curve [ ti =f( @)I determine the rate of fall of the two components of total soil water potential, but as a consequence the water uptake by crops, and hence the yields, are expected to suffer. Therefore, it is usually considered that irrigation of saline soils should be more frequent because it reduces the cumulative water deficits (both matric and osmotic) between irrigation cycles. However, such an opinion is still controversial, as small irrigation intervals subsequently induce water uptake from shallow soil layers, increase unproductive evaporative losses from the soil surface and, with saline irrigation, increase the salt load of soils. Moreover, the non-saline soil water stored from the monsoon rains may also be displaced too deep for plant roots to reach because of the added saline solutions (Minhas and Gupta, 1992). Sinha and Singh (1976a) and Sinha and Singh (1976b) have shown that soil solution concentrations adjacent to growing roots in saline soils are 1.52-fold higher than in the bulk soil. The wetter the soil and the higher the transpiration rate the larger the differences, indicating that keeping the soil wet by decreased irrigation intervals may actually enhance the effects of salinity. Extended irrigation intervals, on the other hand, usually result in deeper roots and larger proportions of water extractions from deeper zones. Reductions in water uptake and thus in ET losses occur under saline conditions. This, in turn, means that higher salinity soils will retain more water than low salinity ones between irrigations, and such a situation should moderate the total water stress and thus reduce the inhibitory effects on growth of increases in solution concentration (Shainberg and Shalhevet, 1984). The net results of these counteracting processes await further experimentation, but based on model predictions, Minhas and Gupta (1993b) have shown that the amount of applied water should also be reduced if the benefits from small irrigation intervals are to be achieved. Because the infiltration rate controls the application depth, it is difficult to apply more than 25 mm of water by surface methods, and irrigation that is too frequent may in fact lead to aeration problems. This points to the need for micro-irrigation systems with very frequent applications of small amounts of water. This aspect is discussed in a later section on ‘Methods of Irrigation’. 3.2. Pre-irrigation The primary objectives of pre-sowing irrigation are the creation of optimal soil moisture conditions to facilitate tillage and seed bed preparation, and to re-charge the prospective root zone with water for the germination and later ET needs of crops. In saline soils, this should also include the leaching of soluble salts below the seeding zone, because germination and seedling establishment are the most critical periods and failures at this stage cannot be rectified later on. Plants are also known to tolerate salinity better

P.S. Minhas/Agricultural Table 3 Yields and water extraction ECiw (dS m-l)

Mungbcan 0.3 (throughout) 4.7 (throughout) 4.7 (PInswl Sorghum * 0.3 (throughout) 4.7 (throughout) 4.7 (Plnsw) Indian mustard 0.3 (throughout) 12.3(throughout) 12.3(PInsw) PInsw = Presowing

patterns following

7

Water Management 30 (1996) 1-24

the use of different

salinity waters

Seed yield

Water extracted (cm) from layer km)

(q haa’)

O-30

30-60

60-90

90- 150

Total

25.2 2.7 15.6

27.8 16.6 23.4

9.7 5.8 9.7

4.0 0.2 4.2

3.3 0.7

44.8 22.6 38.1

97.0 65.0 85.0

18.4 17.0 19.1

7.7 5.1 6.9

2.6 2.0 3.7

2.3 0.5 2.0

31.0 * * 24.7 31.7

23.2 10.5 18.0

19.5 10.7 13.7

9.0 5.1 7.7

6.2 1.8 4.8

2.2 0.5 1.7

36.9 18.1 27.9

irrigation

with non-saline

water,’

Dry forage yield, * * up to the last irrigation

only.

with ageing. Crops such as mungbean, sorghum and mustard were shown to tolerate higher salinity when non-saline water was used for pre-sowing irrigation to leach out the salts in the seeding zone (Minhas et al., 1989; Minhas et al., 1990a; Minhas et al., 1990b). This substitution markedly enhanced germination, crop growth and yields, and also resulted in better utilisation of soil water even from the lower soil layers (Table 3). Pre-sowing irrigation assumes an even more critical role in the success of summer crops. 3.3. Multi-quality

irrigation practices

Under most saline situations in India, canal water supplies are either uncertain or in short supply, so that farmers are forced to pump saline ground/drainage water to meet crop water requirements. Water from these two sources can be applied either separately or mixed together. Mixing water to an acceptable quality for crops also results in improving stream size and thus enhances uniformity of irrigation, especially for the surface method practiced on sandy soils. Allocation of the two types of water separately, if they are available on demand, can be to different fields, in different seasons or at different crop growth stages, so that higher salinity water is not applied to sensitive crops/growth stages. As pointed out earlier, germination and seedling establishment have been identified as the most sensitive stages for most crops. Therefore, the better quality water should be utilised for pre-sowing irrigation and early stages of crop growth. It is then possible to switch over to saline water later, when the crops can tolerate higher salinity. Rhoades et al. (1992) have also advocated a strategy of seasonal cyclic use, called ‘dual rotation’, where non-saline water is used for salt-sensitive crops and for the initial stages of tolerant crops to leach out salts accumulated from irrigation with saline water to previously grown tolerant crops. This type of management strategy may be useful for arid climates with very low rainfall, but it is a natural occurrence in a monsoonal climate. Thus in India the options for using multi-quality water will be either

8

Warer Management 30 (1996) I-24

P.S. Minhas/Agriculmxl

2CW:ISW

-A

ICW:ISW2RYO*18~8+0BORYe

do loo _-x E P @ & : C

3 r*.

I RYO

-*

= 342+

0.66

ICW: 2S.W 3 RYO- 13.5 + 005 I:I line

RYe . X

RYe

..

4

giqf?f

xAd

‘A

EOX

0 RY P/J with bknding

Fig. 3. Relative yields of crops with mixed fresh and saline irrigation sources, at the same average salinity of applied water.

water, or alternate

use of these water

mixing or cyclic use, mainly during the growth of winter crops. If it is presumed that the prerequisite facilities for mixing exist, and that different qualities of water are simultaneously available on demand, then the question arises as to which option should be followed. Analysis of a large number of multi-locational trials with different crops, conducted under the All India Coordinated Research Project (AICRP) on saline water (Minhas and Gupta, 1992), showed that at the same level of EC,,, the yields for different patterns of cyclic use were higher than the estimated yields for mixing (Fig. 3). The advantages gained from various patterns of cyclic irrigation were in the order (2C: IS> > (1C: 1S> > (lC:2S), where C and S indicate irrigation with canal and saline water, respectively. The differences between observed and estimated yields were greater at low relative yields, indicating increased benefits from cyclic use at higher EC,,. This provides useful evidence that multi-salinity water should be used cyclically; canal water should be used in the early stages of crop production, and the use of saline water should be delayed until later. Experiments by Naresh et al. (1993a) and Naresh et al. (1993b) where saline (EC,, 12 dS m- ’> and canal water was combined for cotton-wheat and pearl millet-mustard rotations, and those by Sharma et al. (1994) where both drainage (EC,, 12.5-14.5 dS m-l> an d canal water was used in a pearl millet-wheat rotation, also support the suitability of the cyclic use strategy described above (Table 4). A survey of farmers using saline water (Bouwmans et al., 1988) indicated that alternating canal and saline water resulted in higher production of cotton and millets than mixing the water, whereas mixing proved to be generally beneficial for wheat and mustard. 3.4. Methods of irrigation The distribution of water and salts in soils varies with the method of irrigation. Surface irrigation methods, including border strips, check basins and furrows, are the

P.S. Minhm/Agricultural

Water Management 30 (1996) l-24

Table 4 Effect of various cyclic use and mixing modes of irrigation yields (Mg ha-

9

with canal and saline waters on wheat and mustard

’)

Treatment

Mustard without WT

Wheat without WT

Wheat in soil with WT

Canal water, CW 1CW:lSW 2 CW2 SW 1SW:lCW 1 CW:rest SW Mixing(l:l)

2.05 1.96 1.66 1.87 1.80

5.14 4.91 4.71 4.77 4.03 4.43

6.22 5.83 5.86 5.66 5.20 _

Saline water, SW

1.17

3.07

4.62

ECw = 12 and 12- 15 dS mat latter site.

’ at sites without and with water-table and presowing irrigation with canal water

oldest and most commonly practiced in most parts of India. Even after following the best design criteria, these irrigation methods generally result in excessive irrigation and non-uniformity in water application. Consequently on-farm irrigation efficiency is low (60-70%). However, properly designed and operated surface irrigation methods can maintain the salt balance and minimise salinity hazards. To meet these twin objectives, land needs to be properly levelled to ensure even distribution of water. Parameters such as the length of the water run, stream size, the slope of the soil and the cut-off ratio, which influence the uniformity and depth of water application for a given soil type, should closely follow the desired specifications (Rajput and Aggarwal, 1983). High-energy pressurized irrigation methods such as sprinklers and drips are typically more efficient as the quantity of water to be applied can be adequately controlled, but the initial investment and maintenance costs of such systems are high. Application of highly saline (EC, 12 dS m- ’> water through sprinklers was observed to be detrimental to pearl millet and cotton, whereas it could safely be used for wheat and barley (Aggarwal and Khanna, 1983). Water-use efficiency, although it decreased with increasing salinity of the water, was higher when the water was applied to winter crops (wheat and barley) by using sprinklers rather than by a surface method. For saline water use, sprinklers are best operated in the evening or at night, when evaporation rates are lower. Sprinklers also ensure uniform distribution of water even on undulating and sandy terrains, and can even help in the better leaching of the salts. The lower pore-water velocity and the lower water content at which water moves in soil under the sprinkler method reduce the preferential flow and increase the efficiency of salt leaching. However, saline water use through sprinklers may cause leaf burning and toxicity when used on some sensitive crops. A general standard for the relative sensitivity of crops to foliar injury from saline water has yet to be worked out for Indian agro-climatic conditions. The use of drip-irrigation has revolutionised the production of some high-value crops and orchards in countries such as Israel and elsewhere, especially when saline water is used. Although drip-irrigation systems are still in their infancy in India, they clearly have great potential in arid and semiarid regions, particularly for light-textured soils. A

10

P.S. Minhas/Agricultural

Water Management 30 (1996) I-24

regular and frequent water supply is possible with a drip system of crop irrigation, and this has been shown to raise the threshold limits of salt tolerance in crops (see Table 5, Case 2, as described later) by modifying the patterns of salt distribution and the maintenance of constantly higher matric potentials (Meiri and Plaut, 1985). Because of enhanced leaching and the accumulation of salts at the wetting front and in the soil between the drip laterals, the salt accumulation below the drippers remains very low while the water content is maintained at a high level at these sites. As crop roots are known to follow the path of least resistance, most roots are found below the surface drippers. Hence, a drip system seems to be the best method of saline water application as it avoids leaf injury to plants, which happens with sprinklers, and maintains optimum conditions for water uptake by roots. Improvements in yield and water-use efficiency, as well as in the size and quality of vegetables even with the use of saline water, was reported by Singh et al. (1978) and Aggarwal and Khanna (1983). The major drawback of irrigation with drippers is the high salt concentration that develops at the wetting front. Accumulated salts cause problems when subsequent crops are planted because the effective leaching of these salts would require the use of flood- or sprinkle-irrigation. Another problem is the clogging of drippers by precipitated salts. Some of the indigenous alternatives to drips which have been tried on a micro-scale are the use of pitchers (Mondal et al., 1987) or specially designed earthen cups (Yadav, 19861, but their feasibility on a larger scale in the field remains untested.

4. Shallow watertable management To minimise the salinity hazards where there is a high watertable, the salts are usually leached down and waterlogging problems alleviated by the installation of a sub-surface drainage system. Since the drainage waters contain considerable amounts of salts, and sometimes toxic elements also, their disposal to natural outlets often creates problems. A potential solution to reduce drainage volumes could be to promote exploitation of the watertable to meet part of the water needs of the crop. Several reports have indicated that substantial contributions to seasonal evapo-transpiration can come from shallow watertables. Optimum yields of wheat have been obtained with only one irrigation where there was a non-saline shallow (1.2 ml watertable (Rajput and Aggarwal, 1983). Crops have also been shown to be able to get much of their water requirement from a shallow saline watertable (Grimes et al., 1984). For a wheat crop grown on a sandy loam soil having a saline watertable (EC,, 8.7 dS m- ’> at about 1.7 m depth, Minhas et al. (1988b) observed that the ground water contribution was increased by eliminating post-sowing irrigation with saline water (EC,, 6.4 dS m- ’), and was highest (50%) under non-irrigated conditions. The use of ground water by crops is also related to its depth and salt content (Chaudhary et al., 1974; Minhas et al., 1989; Minhas et al., 1994a). Although maximising crop water use from shallow ground water can reduce the volume of drainage effluents, it was often thought that such a practice would simultaneously lead to salt accumulations in the rooting zone. However, latter studies have shown that the amount of salt left in the rooting profile in the post-monsoon period varies very little because of leaching by rain.

P.S. Minhns/Agricultural

Water Management

30 11996) 1-24

11

In addition to the tapping of saline water by inducing uptake by crop roots in inland salinity zones, a system of skimming called ‘dorouv’ technology has been used in coastal areas for many years (Gill and Abrol, 1990; Subbaiah et al., 1991). A unique feature of ground water (of depth varying between 0.5 m and 3.0 m) in the narrow sandy belt along sea coasts is the formation of a freshwater layer by infiltrated rainwater that floats on the saline water encroaching from the sea. Farmers have been utilising this phenomenon by digging pits and excavating small quantities of fresh water. To improve freshwater yields, this technology has been refined by installing lines of tiles radially along the pumping units, and the water is used for raising nursery/crops under sprinklers.

5. Crop management Tolerance to salinity varies a great deal, almost lo-fold amongst crop plants and to a lesser extent amongst their genotypes. These inter- and intragenic variations in the salt tolerance of plants can be exploited to select crops/cultivars which produce satisfactorily under a given root-zone salinity. Information on crop tolerances to salinity and saline water can be obtained from Maas (1986), and on the use of saline water in different agro-climatic zones in India from a recent compilation by Minhas and Gupta (1992). The relative effects of various management practices and other factors on the values of tolerance parameters of some crops with respect to saline water are summarised in Table 5. These have been differentiated into four possible types of modification in a piece-wise linear response curve, as described by Meiri and Plaut (1985). These are: Case 1, simultaneous changes in threshold salinity (EC,) and slope (S) while maintaining zero yield salinity (EC,); Case 2, simultaneous changes in EC,, S and EC,; Case 3, changes in S and EC, only; Case 4, changes in EC, and EC, only. In some experiments there were several interacting variables, and collinearity existed in the salinity data because the salinity of each successive stage was dependent on the salinity of the previous stage. Therefore, to remove multi-collinearity of salinity and other variables over the years, independent estimates of responses to salinity were derived from multiple regressions with dummy variables. Details of the usefulness of such an analysis in making management decisions are described below. 5.1. Growth stages Not all crops tolerate salinity equally well at different stages of their growth. During the initial stages of growth the root interaction zone is limited to a few inches below the surface, where most salts are concentrated after evaporation. Hence, germination and early seedling establishment are the most critical stages of most crops for saline irrigation (Minhas and Gupta, 1992). The other critical periods are during the phase changes from vegetative to reproductive growth, i.e. heading and flowering to fruit setting. Apart from this stage, the general tolerance of crops to the use of saline water increases with their increasing age (Table 5). An increase in EC, and a decrease in S with plant development in crops such as wheat, mustard and mungbean, as reported by

Mungbean

-do-

Temperatures, evaporative demand and water table soil texture

c. Agro-ecological

Irrigation method

Mustard

Wheat

Wheat

conditions

Potato

Mustard

-do-

b. Irrigation

Wheat

Combined use of saline and non-saline water

a. Growth stages

Crop

High (Dharwad) Low (Agra) Low(Sampla) WT loamy sand, Jobner sandy loam, Agra silty caly loam loamy sand, Jobner sandy loam, Agra silty caly loam

Sprinkler Drip

RY = RY= RY = RY = RY = RY = RY = RY= RY=

100 - 4.9(ECe - 0.9) IOO-4.1(ECe-3.8) IOC- 8.2(ECe-3.9) loO- 4.4(ECiw - 6.0) IOO-3.9(ECiw-4.0) 100 - 4.2(ECiw - 1.O) 100 - 2.2(ECiw - 2.0) IOO-6.!XECiw-5.1) IOO-3.7(ECiw-1.1)

RY=lOO-11.7(ECe-1.1) RY = 100 - 6.3(ECe - 2.6)

RY= IOO-4.l(ECe-3.8) RY = 109.9 - 6.2 ECe RY = 115.7-5.5 ECe RY = 106.7 - 3.4 ECe RY = 100 - 8.5(ECe - 3.8) RY=ll5.6-8.2ECe RY = 168.0- 12.6 ECe RY = 106.6 - 3.3 ECe RY = 100 - 20.7(ECe - 1.2) RY = 1 15.3 - 20.9 ECe RY = 150.3 - 28.5 ECe RY = 157.2 - 24.8 ECe

Response function

and other factors

Time averaged Sowing time Mid season Harvest time Time averaged Sowing time Mid season Harvest time Time averaged Initial to branching Flowering to pod formation Pod development to maturity

Salinity considered

of crop responses to salinity by management

Factor modified

Table 5 Modifications

21.2 28.4 16.1

10.1 17.1

28.4 17.3 21.0 31.1 15.6 14.1 13.3 32.3 6.6 5.5 5.3 6.3

EC,

16.0 10.0 17.5 16.8 12.9 24.9 12.3 14.7

11.0

5.4 10.5

16.0 9.7 11.9 16.7 9.7 8.0 9.4 17.1 4.2 3.1 3.6 4.3

EC,, (dS m-‘1

Case

Sharma et al. (1991) AICRP-Saline water

AICRP - Saline Water

Meiri and Plaut (1985)

Minhas et al. (1990aJ

Naresh et al. (1993b)

Naresh et al. (1993a)

Reference

* Functions not written as per equation (1) were derived from multiple regression with/without dummy variables.

4. Ionic constituents/applied nutrients RSC water Wheat Y = 10.66-O.O8l(pH)’ -0.018ECeXSARe+0.88X 10. ‘(SARe)’ Levels of RSC ECeforY=3Mghaa’ neutrlisation RY= 4.90-0.18 ECe 10.5 pHs.sSARe,e with gypsum 4.8 RY = 5.60-0.54 ECe PHs.sSARe,a RY = 4.19-0.18 ECe 6.6 pHs.aSARe,o 3.5 RY = 4.89 - 0.54 ECe pHs.eSAReao ECw and SARw Wheat RY = 98.14-0.54ECiw -SARw(O.lOECiw -0.45)-0.Ol(SAR~)~ ECiw for RY = 90% SARw = 5 RY= 100.14- 1.04ECiw 7.8 = 10 RY = 101.64- 1.54 ECiw 7.6 = 20 RY = 103.14-2.54 ECiw 5.2 = 30 RY = 103.64- 3.54 ECiw 3.6 =4O RY = 106.14-4.54ECiw 2.2 Cl:SO, ratio(R) Wheat Y=3.l44-0.047ECiw-l.ll5Xl0~Z-0.229Xl0~4P2-O.ORZ-0.035ECiwXR-6.l67Xl0~4ECiwXP-0.4lXl0~3RXP Applied P (kg ha- ’) ECiw for Y = 3.5 Mg ha- ’ Y = 4.501-0.130 ECiw 7.7 P26R0.3 P26R3,0 Y = 4.328-0.121 ECiw 6.8 P26R5.0 Y=3.858-0.114ECiw 2.1 P39Ro.3 Y = 5.040 - 0.173 ECiw 8.9 P39R3.0 Y = 4.943 - 0.164 ECiw 8.8 “39%0 Y = 4.530 - 0.157 ECiw 6.7 Chauhan et al. (1991)

Singh et al. (1992)

3

3+4

Sharma et al. (1993)

4

14

P.S. Minhas/Agricultural

Water Manugement 30 (1996) 1-24

Naresh et al. (1993a), Naresh et al. (1993b) and Minhas et al. (199Ob), represent Case 2. In a lysimetric experiment with wheat where initial salinity profiles and patterns of salts added during growth were varied while keeping the total salt input constant, Minhas and Gupta (1993a) observed that the EC,, values increased from 9.3 dS m- ’ at the crown rooting stage to 13.2 dS m-’ at the dough stage, and yields were best related to weighted root-zone salinity, which is calculated by giving each figure a weighting according to rooting density over time. Thus, for the non-steady conditions which exist under a monsoonal climate, salt tolerance at critical stages of crop plant growth changes in response to salinity, with the method of salinisation and the initial distribution of salts needing to be considered in order to produce an effective description of crop responses to saline irrigation. 5.2. Crop cultivars In addition to intergenic variations of crops in their toleration of salinity, a variation in the inherent salt tolerance of crop cultivars also exists. Generally, there is a negative (Case 2) correlation between the tolerance of varieties and their potential yields. Hence, there are not many varieties which are both tolerant to salinity and produce an economic yield, which is the major consideration for most farmers. For example, cultivars such as ‘Damodar’ rice and ‘Kharchia’ wheat are well documented for their salinity tolerance but have low yield potentials. Farmers prefer vigorously growing and high-yielding varieties like ‘Jaya’ rice and ‘HD-2304’ wheat even though they have a low tolerance to salinity, simply because these may still outyield their tolerant counterparts. Now, however, cultivars such as ‘HD-2560’ wheat, ‘DIRA-342’ mustard and ‘MESR-16’ cotton suggest that it is possible to breed cultivars with a high yield potential as well as higher salt tolerances, although the selection of crop cultivars showing stability under salinity should be preferred. 5.3. Soil and environmental

conditions

Environmental factors such as temperature, atmospheric evaporativity, etc., also markedly influence the salt tolerance of crops. When wheat was grown in a comparatively cooler climate (i.e. low ET demands during the growth period) at Agra in Northern India EC, and EC, increased, while there was a decrease in EC, for wheat grown at Dharwad in the south (Table 5, Case 11. Studies by Sinha and Singh (1976b) showed that the salt content of soil adhering closely to crop roots was much higher than that in the bulk soil (1.3-2.0 times), and was linearly related to the total amount of water transpired by maize and wheat plants as well as to the water transpired per unit root length. Based upon these studies, it was pointed out that the salt stress to which plants will be subjected is determined by transpiration rates vis-a-vis evaporative demands for water. Similarly, although the threshold EC, did not vary in the presence of a shallow and saline water table (Sharma et al., 1991), it did increase the slope (Case 1). The role of soil texture in defining the limits of saline water usage is also shown in Table 5 for two crops, wheat and mustard (Case 2). These results are obviously due to higher leaching fractions resulting from surface irrigation methods, which also mean a

P.S. Minhas/Agriculrural

Water Manugemenr 30 (1996) 1-24

1.5

slower salinity build-up in coarser soils as well as higher leaching of accumulated salts with monsoon rains. In rabi crops, values such as 1.8, 1.12 and 0.9 for EC, at harvest and for EC,, have been given for soils having a clay content of > 20, lo-20 and < lo%, respectively (Singh and Bhumbla, 1968; Paliwal and Mehta, 1973; Verma, and Lal, 1991). 1973; Pal and Tripathi, 1979; Manchanda et al., 1989; Khandelwal However, when these values were converted to field-capacity water content (Minhas and Gupta, 1992) more or less similar factors (2.2-2.4) resulted, indicating that plants interact with similar surface soil salinities in soils varying in texture. 5.4. Ionic constituents

of salinity

In addition to total electrolyte contents, plant responses are also governed by the concentrations of different ions in the soil solution. The associated cations and anions of salinity influence the tolerances of crops by: (1) governing the effective salinity of the soil solution with which the plant roots interact through their control over precipitation and dissolvability, leaching and the dispersive behaviour of soils etc., and (2) direct toxicity due to excessive accumulation of ions in the plant tissues, thus causing nutritional imbalances. Examples of interaction between sodium and calcium under conditions of high-SAR and alkali irrigation water (Singh et al., 1992; Sharma et al., 19931, along with chloride and sulphate dominance in salinity (Chauhan et al., 1991), are included in Table 5. The tolerance of wheat to salinity decreased with an increase in SAR, pH or Cl content (Cases 3 and 4). Manchanda et al. (1991) have also shown that pulse crops such as chickpea, faba bean and pea performed better under sulphate- than chloride-dominated saline conditions at comparable EC, levels. Rhoades et al. (1992) reported that if soil is saline or if the Ca concentration exceeds about 2 mmol l- ‘, even a high level of SAR, as distinguished from salinity, will have little nutritional effect on most crops and can be ignored. Thus, the major problems with respect to sodium toxicity or calcium nutrition should occur under relatively less saline but sodic and alkaline pH conditions when Na concentration is high and Ca concentration is low, and/or where the Mg/Ca ratio exceeds three. Otherwise reduced salt tolerance is more likely to be caused by structural deterioration, leading to poor physical conditions. However, in a long-term experiment, sodicity-induced accumulation of salts with the use of high-SAR water was observed to be the main cause of yield reductions (Chauhan et al., 1991). Further analysis revealed that the yield reductions of pearl millet grown during the monsoon depended on the amount of rainfall received (Fig. 4). It can be expected that increased rainwater would reduce the effects of salinity due to dilution and salt leaching, but higher reductions in pearl millet yields with increased SARi, were ascribed to water stagnation problems.

6. Chemical 6.1. Fertiliser

management use

Several studies to evaluate the concept of alleviating salinity stress through enhanced fertility have shown that a strategy of additional application of fertiliser nitrogen to

16

P.S. Minhas/Agricultural

Water Management

30 (1996) 1-24

15f ;; 9

to-

:

5-

0

I

I

I

I

I

I

I

I

5

IO

I5

20

25

30

35

40

’

SARiw

Fig. 4. Predicted

EC,

for attaining 75% yields of wheat and pearl-millet

as affected by SAR iw and rainfall.

reduce/overcome the adverse effect of salts may not be satisfactory (AICRP, 1994). In general, when salinity is not a yield-limiting factor, the applied nitrogenous fertilizers will increase the yields of crops proportionately more than when the salinity becomes a limiting factor (Dhir et al., 1977; Dayal et al., 1995). On the other hand, increasing the level of phosphorus above the recommended dose mitigates the adverse affects of salinity, especially when chlorides are the dominant anions in the saline water rather than sulphates (Manchanda et al., 1982; Chauhan et al., 1991). The results presented in Table 5 show that application of phosphatic fertilisers will probably improve the threshold limits of crops to the use of chloride-dominated saline water (Case 3). In addition to structural improvements, incorporation of organic/green manures have added advantages in soils irrigated with saline water in several ways. (i) Because of the sensitivity of the nitrification process to salinity (Garg et al., 1982; Sen and Bandopadhyay, 1987), losses through NH, volatilisation are aggravated. Thus, the manure can serve as a temporary bonding agent for the ammoniacal pool of nitrogen and reduce losses. Experiments (AICRP, 1994) show an increased response to N-fertilisers in the presence of organic materials, which suggests that they do reduce volatilisation losses and enhance N-use efficiency. (ii) Farmyard manure has a beneficial acidifying effect on the sodicity of the soil both through the action of organic acids formed during its breakdown, and because the Ca + Mg contained in farmyard manure replaces the Na from the exchange complex. Therefore, addition of organic materials would help the reclamation process by reducing pH and exchangeable sodium in soils. (iii) Because of small and less active microflora in saline soils, mineralisation of organic nutrient fractions is comparatively low. So the retention of nutrients in organic forms for longer periods will guard against their leaching and other losses. 6.2. Need for amendments The presence of high sodium in relation to calcium content in soils increases the pH and ESP, which in turn decrease the soil permeability to water and can also cause

P.S. Minhas/Agricultural

Water Management

30 11996) l-24

17

100 n infiltration mte with

? ?Canalwater 0

s

Saline water

60-

a E

40-

20-

O-

kzillJ 12,20

12,40

Water quality (ECw,!SARw)

Fig. 5. Effects of long-term use of water of various salinities and SAR on the steady infiltration rate of a sandy loam soil. RIR denotes infiltration rate with reference to the rate of 2.25 cm h- ’ of the original soil .

nutritional imbalance within the plants. The adverse effects of high Na on the physical and chemical properties of soils can be mitigated by the use of amendments which contain calcium, e.g. gypsum. Acids or acid-forming substances such as sulphuric acid or pyrites which on reaction with soil CaCO, release Caf in solution can also be used. Whether or not to use amendments for saline-sodic conditions should be judged from their effectiveness in improving soil properties and crop growth in relation to the cost involved. It is usually considered that the Ca content in highly saline soils will always be more that the critical (> 2 mmol 1-l) level required for plants, and desodication and desalinisation occur simultaneously when such soils are leached, but there are instances where leaching of saline-sodic soils leads to a rise in their pH, as well as dispersion and disaggregation (Sharma and Khosla, 1984; Minhas and Sharma, 1989). Moreover, high SAR-saline soils are prone to infiltration and water stagnation problems, mainly during monsoon rains (Minhas and Sharma, 1986) and the changes are irreversible (Fig. 5) when the long-term consequences of using high-SAR saline water are considered (Minhas et al., 1993). This is contrary to the general belief that saline water with electrolytic concentrations higher than flocculation values will help regain infiltration capacity. With the movement of clay during cycles of irrigation with saline water and rainwater infiltration during monsoons, steady infiltration rates are controlled by layers below the plough layer where re-mixing of soil separates is not expected to occur. Such soils require small additions of amendments such as gypsum to maintain electrolyte concentrations for the stability of aggregates during rain infiltration and hence help in avoiding or alleviating problems of such reduced infiltrability. Since reduced infiltration and crusting problems may also result from the use of saline water with Mg:Ca > 3 (Girdhar and Yadav, 1980; Yadav and Girdhar, 1981) and rich in silica (Goyal and Jain, 1982) the use of gypsum may prove beneficial.

18

P.S. Minhas/Agricultural

Water Management

30 (1996) 1-24

6.3. Cultural practices 6.3.1. Planting procedures Failure to achieve satisfactory germination and thus the required plant population is the major factor limiting crop production with saline water. Crops such as wheat, barley and safflower, although they can tolerate fairly high levels of salinity when mature, are very sensitive at the germination and early seedling stages. Thus, planting practices should ensure a suitable environment in the seeding zone. Conventional seeding of most crops is done when optimum moisture conditions for tillage and seedbed preparation are attained following pre-sowing irrigation. After the application of pre-sowing irrigation, the movement of salts towards the surface via evaporative drying both up to the time of seeding and during the periods of germination and emergence exposes the seeds to soil water of higher salinity, especially when saline irrigation is practiced (EC,, > EC,,). This makes seed germination and emergence even more critical, especially for summer crops seeded under high evaporative conditions. Therefore, the objectives of pre-sowing irrigation should include leaching out the salts in the seeding zone by a heavy application of non-saline water wherever possible. Another technique which seems to help in the establishment of crops is to use post-sowing irrigation to push the salts deeper into the soil and to maintain better moisture conditions (Minhas et al., 1988a). However, the timing of this irrigation should be such as to avoid any subsequent crusting problem. In a field experiment, Indian mustard was seeded with saline water being used for both pre- and post-sowing irrigation (Table 6), and the results were compared with the potential best available water. The seed yield with dry seeding followed by post-sowing irrigation with saline water was sustained up to 11 dS m-l. Modifications in the shape of the seed beds can also reduce salt accumulation near the seed. Nalamber and Dastane (1969) reported that sowing near the bottom of the furrows on both sides of the ridges (50 cm wide) in a soil having an EC, of 4.7-5.2 dS

Table 6 Effect of seeding method for use waters on crop stand and yield of Indian mustard ECiw (dS m-l)

Seeding method SM,

SM?

Plant stand (no. m 3 7 I1 16

10.4 9.8 2.4 1.4 Seed yield kg ha-

3 7 11 16

1670 1740 590 190

SM,

‘) 10.6 10.7 9.3 6.3

10.0 9.7 7.4 2.5

’)

SM, = Seeding after conventional presowing irrigation. SM, = Dry seeding followed by post-sowing irrigation. SM, = l/2 pre-and l/2 post-sowing irrigation.

1560 1620 1540 1290

1510 1570 1380 750

P.S. Minhus/Agricultural

Water Management

30 (1996) l-24

19

m- ’ did not increase yield of barley as compared with sowing on the flat. However, in the case of radish, since direct injury to leaves could be avoided, ridge and furrow sowing was much better than flat sowing. The other alternatives are to apply irrigation in alternate rows and to seed on the northeast side of the ridges (Bains and Singh, 1966), because the salts move to the drying surfaces along with the water and accumulate there. The EC, values for the southwest, top and northeast sides of the ridges (60 cm apart, 25 cm high) were 35.4, 24.4 and 6.7 dS m- ’, respectively, although the soil initially had an EC, of 15.5 dS m -’ (Bains and Singh, 1966). For crops with larger seeds, they can be planted in the furrows (Rai and Mehrotra, 1971). The advantage of such a practice can be that the seed will be placed in a wet but less saline zone, because when the ridges are made a greater proportion of the saline surface soil goes into the ridges, and post-sowing irrigation will leach the salts in the furrow soil more efficiently than those in the ridge soil (Minhas et al., 1988a). Similarly, Yadav (1993) reported the beneficial effects of furrow planting with mustard and sorghum over flood-irrigation with saline water. In addition to the creation of favourable water regimes in the rooting zone during irrigation of tree saplings planted in furrows (2.5 m apart), this method had the advantage of pushing the salts towards inter-row areas in monsoon rains. Thus, the concept of furrow planting has also been utilised to create favourable ‘niches’ for the establishment of tree plantations with saline irrigation (Minhas et al., 1994b; Tomar et al., 1994). 6.3.2. Row spacing/plant density As stunted growth and poor tillering of crops are the major causes of yield reductions in crops irrigated with saline water, the crop yield, which is the product of stand density (number of plants or tillers per unit area) and yield per plant or tiller, should increase if the density of stunted plants is increased. This can be achieved by narrowing the interrow and/or intrarow spacings of row crops. Studies with wheat (AICRF’, 1994) have shown lo-15% improvements in its grain yield when seeded with 25% extra seed compared with the yield when the crop was thinned to maintain a plant population as recommended for normal soils (Table 7). 6.4. Tillage / mulching Tillage and other moisture conservation practices play a crucial role in salt leaching during monsoons, when most soils irrigated with saline water remain fallow. The

Table 7 Effect of population SARiw

*

on grain yield of wheat

Wheat yield (Mg ha- ‘) at seed rate

IO 20 30 40 Canal water * ECiw 8-12

density and saline irrigation

dSm_‘,

**

Normal

25% extra

Mean

3.85 3.66 3.35 3.06 4.49

4.28 4.23 3.93 3.72

4.07 3.95 3.64 3.39

* * Average for 1991-1992

and 1992-1993.

20

P.S. Minhas/Agricultural

Water Manqement

30 (1996) l-24

emphasis in a monsoon climate should be to maximise the infiltration of rainwater into the soil and minimise its losses due to run off and evaporation during the periods in between rains. To achieve this the fields should be properly levelled and bunded, and surface soil should be kept open and protected against the beating action of raindrops. This can be achieved by ploughing in periods between the rains and by adopting other water conservation practices. As well as increasing the intake of rainwater, ploughing also helps in controlling the unproductive losses of water from weeds and evaporation. This practice will also reduce the upward movement of salts between rainfall events and increase salt removal by rain. Creation of a soil mulch during the redistribution periods was observed to enhance the leaching of surface-applied salts by lo-13% (Minhas et al., 1986; Minhas and Khosla, 1987). Use of straw mulches can also enhance leaching of salts by rainfall, but shortages of straw in saline areas is a serious impediment to adopting this practice.

7. Guidelines for using saline water It is evident from the above discussion that in order to determine the suitability of a specific water for irrigation purposes, it is necessary to know not only its composition, but also the exact conditions of its proposed use (soil, climate, crops etc.), the method of irrigation, and other management practices followed. Because of inherent problems in integrating the effects of all these factors, rigid water-quality standards for universal use are difficult to develop. Therefore, broad guidelines for assessing the suitability of irrigation water have been suggested from time to time for average use conditions. In 1990, a committee of consultants recommended guidelines for utilising poor-quality water and their wider applicability in different agro-ecological zones in India (Table 8). To meet site-specific water-quality objectives, factors such as water-quality parameters, soil texture, crop tolerances and rainfall have all been considered. Some of the addenda

Table 8 Guidelines

for using saline irrigation

Soil texture (% clay)

Crop tolerance

Fine

Sensitive Semi-tolerant Tolerant Sensitive Semi-tolerant Tolerant Sensitive Semi-tolerant Tolerant Sensitive Semi-tolerant Tolerant

( > 30) Moderately fine (20-30) Moderately coarse (10-20) Coarse (< 10)

waters in India ECiw (dS m-

‘) limit for rainfall region

< 3.50

350-550

> 550 mm

1.0

1.0 2.0 3.0 2.0 3.0 6.0 2.5 6.0 8.0 3.0 7.5 10.0

1.5 3.0 4.5 2.5 4.5 8.0 3.0 8.0 10.0 3.0 9.0 12.5

1.5 2.0 1.5 2.0 4.0 2.0 4.0 6.0 6.0 8.0

P.S. Minhas/Agricultural

Water Management 30 (1996) 1-24

21

added to these guidelines have included the following points: (1) the use of gypsum for saline water having SAR > 20 and/or Mg:Ca > 3 and rich in silica; (2) fallowing during the rainy season when SAR > 20 and high-salinity water is being used in low-rainfall areas; (3) additional phosphorous application, especially when the Cl:SO, ratio is > 2.0; (4) the use of canal water at early growth stages, including pre-sowing irrigation, in conjunction with saline water; (5) using 20% extra seed and irrigating very soon after sowing (within 2-3 days) to improve germination; (6) when EC, < EC, (O-45 cm depth of soil at harvest of rabi crops), irrigation with saline water just before the onset of the monsoon will lower the soil salinity and raise the soil moisture, resulting in greater salt removal by the rains; (7) the use of organic materials in a saline environment to improve crop yields; (8) for soils having either a shallow watertable (within 1.5 m for a crop sown just before the monsoon) or hard subsoil layers, the next lower EC,, and/or alternate types of irrigation (canal/saline) are applicable.

Acknowledgements The author expresses his gratitude to Drs. H.R. Manchanda, Raj K. Gupta, D.R. Sharma and other colleagues for useful discussions. Thanks are also due to Dr. N.K. Tyagi, Director of the Institute, for his encouragement and providing the necessary facilities.

References Aggarwal, M.C. and Khanna, S.S., 1983. Efficient soil and water management in Haryana. Bull. Haryana Agricultural University, Hisar, p. 118. AICRP, 1994. ICAR All India Coordinated Research Project on Management of Salt-affected Soils and Use of Saline Water in Agriculture, 1972-1993. Annual Reports, CSSRI, Kamal. Ayers, R.S. and Westcot, D.W., 1985. Water Quality for Agriculture. Irrigation and Drainage Paper No. 29, Rev. 1, FAO, Rome, p. 174. Bains, S.S. and Singh, K.N., 1966. Utilization of solar radiation in desalinisation of ridged plant beds on saline soils. Nature, 212: 1391-1392. Bouwmans, J.H., vanHoom, J.W., Cruiseman, G.P. and Tanwar, B.S., 1988. Water table control, m-use and disposal of drainage water in Haryana. Agric. Water Manage., 14: 537-545. Chaudhary, T.N., Bhatnagar, V.K. and Prihar, S.S., 1974. Growth response of crop to depth and salinity of water and soil submergence. I. Wheat. Agron. J., 66: 32-35. Chauhan, C.P.S., Singh, R.B., Minhas, P.S., Agnihotri, A.K. and Gupta, R.K., 1991. Response of wheat to irrigation with saline water varying in anionic constituents and phosphorus application. Agric. Water Manage., 20: 223-23 1. Dayal, Bhu, Minhas, P.S., Chauhan, C.P.S. and Gupta, R.K., 1995. Effect of supplementary saline irrigation and applied nitrogen on the performance of dryland mustard (Brassica juncea L.). Exp. Agric., 31: 423-428. Dhanker, O.P., Phogat, V.K., Sharma, D.R. and Sangvan, O.P., 1986. Field study on the effect of irrigation water quality on soil characteristics and crop yields. Int. Seminar Water Management in Arid and Semiarid Zones, Vol. II. Haryana Agricultural University, Hisar, 27-29 November 1986, pp. l-10. Dhir, R.P., 1977. Saline waters-their potentiality as sources of irrigation. In: Desertification and its Control. ICAR, New Delhi, pp. 130-148. Dhir, R.P., Bhola, S.N. and Kolarkar, A.S., 1977. Performance of ‘Kharchia 65’ and ‘Kalyan Sona’ wheat varieties at different levels of water salinity and nitrogenous fertilizers. Indian J. Agric. Sci., 47: 244248.

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Garg, B.K., Katuju, B., Vyas, S.P. and Lahiri, A.N., 1982. Influence of soil fertility on growth and metabolism of wheat under salt stress. Biol. Plant., 24: 290-295. Gill, H.S. and Abrol, I.P., 1990. Evaluation of coastal sandy soils and their saline ground waters for afforestation: A case study from India. New For., 4: 37-53. Girdhar, I.K. and Yadav, J.S.P., 1980. Effect of different Ca/Mg ratios, SAR values and electrolytic concentrations in leaching water on the dispersion and hydraulic conductivity of soils. Proc. Int. Symp. Salt-Affected Soils. CSSRI, Kamal, pp. 210-218. Goyal, R.S. and Jain, B.L., 1982. Use of gypsum in modifying crust-conducive conditions in saline irrigated soils. J. Indian Sot. Soil Sci., 30: 447-454. Grimes, R.W., Sharma, R.L. and Handerson, D.W., 1984. Developing the resource potential of shallow water tables. California Water Resources Centre, Contribution No. 198, p. 39. Gupta, I.C. and Abhichandani, C.T., 1970. Seasonal variations in salt compositions of some saline water irrigated soils of Western Rajasthan. J. Indian Sot. Soil Sci., 18: 428-435. Khandelwal, R.B. and Lal, P., 1991. Effect of salinity, sodicity and boron in irrigation water on the properties of different soils and yield of wheat. J. Indian Sot. Soil Sci., 39: 537-541. Khosla, B.K., Gupta, R.K. and Abrol, I.P., 1979. Salt leaching and effect of gypsum application in a saline-sodic soil. Agric. Water Manage., 2: 193-202. Laffelaar, P.A. and Sharma, R.P., 1977. Leaching of highly saline sodic soils. J. Hydrol., 32: 203-218. Maas, E.V., 1986. Salt tolerance of plants. Appl. Agric. Res., 1: 12-26. Manchanda, H.R. and Chawla, K.L., 1981. Soil profile variations and wheat growth under irrigation with highly saline waters in coarse loamy soils in South Western Haryana. J. Indian Sot. Soil Sci., 29: 504-5 11. Manchanda, H.R., Sharma, S.K. and Bhandari, D.K., 1982. Response of barley and wheat to phosphorus in the presence of chloride and sulphate salinity. Plant Soil, 66: 233-241. Manchanda, H.R., Gupta, I.C. and Jain, B.L., 1989. Use of poor quality waters. In: Reviews of Research on Sandy Soils of India. Int. Symp. Managing Sandy Soils. CAZRI, Jodhpur, pp. 362-383. Manchanda, H.R., Sharma, S.K. and Mor, R.P., 1991. Relative tolerance of pulses for chloride and sulphate salinity. Indian J. Agric. Sci., 61: 20-26. Meiri, A. and Plaut, Z., 1985. Crop production and management under saline conditions. Plant Soil, 89: 253-271. Minhas, P.S. and Gupta, R.K., 1992. Quality of Irrigation Water-Assessment and Management. Publication and Information Section, Indian Council of Agricultural Research, New Delhi, p. 123. Minhas, P.S. and Gupta, R.K., 1993a. Conjunctive use of saline and non-saline waters. I. Response of wheat to initial salinity profiles and salinisation patterns. Agric. Water Manage., 23: 125-137. Minhas, P.S. and Gupta, R.K., 1993b. Conjunctive use of saline and non-saline waters. III. Validation and applications of a transient model. Agric. Water Manage., 23: 149-160. Minhas, P.S. and Khosla, B.K., 1987. Leaching of salts as affected by the method of water application and atmospheric evaporativity under shallow and saline water-table conditions. J. Agric. Sci., 109: 415-419. Minhas, P.S. and Sharma, D.R., 1986. Hydraulic conductivity and clay dispersion as affected by the application sequence of saline and simulated rainwater. Irrig. Sci., 7: 159-167. Minhas, P.S. and Sharma, D.R., 1989. Salt displacement in a saline sodic and amended soil using low electrolyte water. J. Indian Sot. Soil Sci., 37: 435-440. Minhas, P.S., Khosla, B.K. and Prihar, S.S., 1986. Evaporation and redistribution of salts as affected by tillage induced soil mulch. Soil Tillage Res., 7: 301-313. Minhas, P.S., Sharma, D.R. and Khosla, B.K., 1988a. Effect of postsowing irrigation and planting techniques on germination of sorghum irrigated with saline water. J. Indian Sot. Soil Sci., 36: 584-587. Minhas, P.S., Sharma, D.R. and Khosla, B.K., 1988b. Effect of quality and depth of ground water table on soil salinisation and crop growth. Amm. Rep. CSSRI, Kamal, pp. 48-5 1. Minhas, P.S., Sharma, D.R. and Khosla, B.K., 1989. Response of sorghum to the use of saline waters. J. Indian Sot. Soil Sci., 37: 140-146. Minhas, P.S., Sharma, D.R. and Khosla, B.K., 1990a. Mungbean response to irrigation with waters of different salinity. Irrig. Sci., 11: 57-62. Minhas, P.S., Sharma, D.R. and Khosla, B.K., 1990b. Effect of alleviating salinity stress at different growth stages of Indian mustard (Brcr.ssica junceu). Indian J. Agric. Sci., 57: 343-346.

P.S. Minhas/Agricultural

Water Munugement

30 (1996) 1-24

23

Minhas, P.S., Naresh, R.K., Chauhan, C.P.S. and Gupta, R.K., 1993. Field determined hydraulic properties of a sandy loam soil irrigated with various salinity and SAR waters. Agric. Water Manage., 24: 93- 105. Minhas, P.S., Sharma, D.R. and Gupta, R.K., 1994a. Soil salinisation and crop yields in relation to quality and depth of ground water. Amm. Rep. 1990- 1994, CSSRI, Kamal. Minhas, P.S., Singh, Y.P., Tomar, O.S., Gupta, R.K. and Gupta, Raj K., 1994b. Saline irrigation and its schedules for Acacia nilotica and Dalbergia sissoo on a highly calcamous soil. In: P. Singh, P.S. Pathak and M.M. Roy (Editors), Agroforestry Systems for Degraded Lands. Oxford and IBH, New Delhi, pp. 357-364. Mondal, R.C., Gupta, S.K. and Dubey, S.K., 1987. Pitcher Farming. Bull. No. 11, Central Soil Salinity Research Institute, Kamal, 15 pp. Nalamber, R.V. and Dastane, N.G., 1969. Cultural practices for crop production under salinity cum high water table conditions. hoc. Symp. Water Management. Udaipur, pp. 251-255. Naresh, R.K., Minhas, P.S., Goyal, A.K., Chauhan, C.P.S. and Gupta, R.K., 1993a. Conjunctive use of saline and non-saline waters. II. Field comparisons of cyclic use and mixing for wheat. Agric. Water Manage., 23: 139- 148. Naresh, R.K., Minhas, P.S., Goyal, A.K., Chauhan, C.P.S. and Gupta, R.K., 1993b. Production potential of cyclic irrigation and mixing of saline and canal water in Indian mustard (Brussica juncea) and Pearl millet (Pennisetum typboides) rotation. Arid Soil Res. Rehabil., 7: 103- 111. Pal, B. and Tripathi, R.K., 1979. Physico-chemical characteristics of soils of a semi-desert tract of UP as affected by irrigation water quality. J. Indian Sot. Soil Sci., 27: 240-248. Paliwal, K.V. and Mehta, K.K., 1973. Boron content of soils irrigated with saline water in Kota and Bhilwara regions of Rajasthan. Indian J. Agric. Sci., 43: 766-772. Rai, B. and Mehrotra, C.L., 1971. Agronomic methods of minimising salt hazards on germination and growth of crops. Proc. All India Symp. Soil Salinity. UP Institute of Agricultural Science, Kanpur, pp. 212-214. Rajput, R.K. and Aggarwal, M.C., 1983. Irrigation and drainage in 2000 A.D. Proc. Natl. Symp. Agronomy in 2000 AD-Looking Ahead. PKV, Nagpur, pp. 7 l-97. Rhoades, J.D., Kandiah, A. and Mishali, A.M., 1992. The use of saline waters for crop production. FAO Irrigation and Drainage Paper No. 48, FAO, Rome, 133 pp. Sen, H.S. and Bandopadhyay, S.K., 1987. Volatilisation losses of nitrogen from submerged saline soils. Soil Sci., 143: 34-39. Shainberg, I. and Shalhevet, J. (Editors), 1984. Soil Salinity Under Irrigation-Principles and Processes. Springer, Berlin, 349 pp. Sharma, D.P., Singh, K.N., Rao, K.V.G.K. and Kumbhare, P.S., 1991. Irrigation of wheat with saline drainage water on a sandy loam soil. Agric. Water Manage., 19: 223-233. Sharma, D.P., Rao, K.V.G.K., Singh, K.N., Kumbhare, P.S. and Oosterbaan, R.J., 1994. Conjunctive use of saline and non-saline irrigation waters in semi-arid regions. Irrig. Sci., 15: 25-33. Sharma, D.R. and Khosla, B.K., 1984. Leaching a sodic water deteriorated salty soil. J. Indian Sot. Soil Sci., 32: 344-348. Sharma, D.R., Sharma, D.K. and Minhas, P.S., 1993. Feasibility studies on the use of saline/sodic waters in conjunction with canal water and amendments. In: N.K. Tyagi et al. @ditors), Sustainable Irrigation in a Saline Environment. CSSRI, Karnal, pp. 1 lo- 117. Singh, B. and Bhumbla, D.R., 1968. Effect of quality of irrigation water on soil properties. J. Res. (Punjab Agric. Univ.), 5: 166-171. Singh, R.B., Minhas, P.S., Chuahan, C.P.S. and Gupta, R.K., 1992. Effect of high salinity and SAR waters on salinisation, sodication and yields of pearl-millet and wheat. Agric. Water Manage., 21: 93-105. Singh, R.B., Minhas, P.S., Chuahan, C.P.S. and Gupta, R.K., 1994. Salt leaching during monsoons and yields of Indian mustard as affected by saline waters of varying Cl/SO, ratios. J. Indian Sot. Soil Sci., 42: 436-440. Singh, S.D., Gupta, J.P. and Singh, P., 1978. Water economy and saline water use by drip irrigation. Agron. J., 70: 948-95 1. Sinha, B.K. and Singh, N.T., 1976a. Magnitude of chloride accumulation near corn roots under different transpiration, soil moisture and salinity regimes. Agron. J., 60: 346-348. Sinha, B.K. and Singh, N.T., 1976b. Salt distribution around roots of wheat under different transpiration Plant Soil, 44: 141-147.

rates.

24

P.S. Minhns/Agricultural

Water Management 30 (1996) 1-24

Subbaiah, G.V., Gupta, R.K., Rao, K.V.G.K. and SubbaRao, IV., 1991. Development of Dorouvu technology for skimming fresh water floating over saline ground water in coastal saline areas of AP. J. Indian Sot. Coastal Agric. Res., 9: 205-206. Tanji, K.K. (Editor), 1990. Agricultural Salinity-Assessment and Management. ASCE Manual No. 71, ASCE, NY, 619 pp. Tomar, O.S., Minhas, P.S. and Gupta, R.K., 1994. Potentialities of afforestation of saline water-logged soils. In: P. Singh, P.S. Pathak and M.M. Roy (Editors), Agroforestry Systems for Degraded Lands. Oxford and IBH, New Delhi, pp. 11 l-120. US Salinity Laboratory, 1954. Diagnosis and Improvement of Saline and Alkali Soils. USDA Handbook No. 60, p. 160. Verma, S.L., 1973. Survey of the quality of some of the typical underground waters in Haryana and their effect on soil properties. MSc. Thesis. Haryana Agricultural University, Hisar, p. 147. Yadav, J.S.P. and Girdhar, I.K., 1981. Effect of different magnesium and calcium ratio and sodium adsorption ratio values of leaching water on soil properties of calcareous and non-calcareous soils. Soil Sci., 13 1: 194-198. Yadav, R.K., 1986., Indigenous auto-irrigation for vegetables. Indian Hortic., 30: 2-5. Yadav, S.S., 1993. Agronomic practices. In: H.R. Manchanda, S.P.S. Karwasra and H.C. Sharma (Editors), Salinity Research at HAU. CCS Haryana Agricultural University, Hisar, pp. 44-46.