Journal of Scientific & Industrial Research 622

J SCI IND RES VOL 70 AUGUST 2011

Vol. 70, August 2011, pp. 622-627

Management of saline irrigation water for enhancing crop productivity R P Jangir1* and B S Yadav2 1

Agricultural Research Station (ARS), Mandor- Jodhpur, 2 ARS, Sriganganagar, S K Rajasthan Agricultural University, Rajasthan, India Received 04 May 2011; revised 28 May 2011; accepted 30 May 2011

This study reviews management of saline irrigation water for enhancing crop productivity. Saline/ alkaline water has been successfully used to augment irrigation supplies and help to raise water productivity. Harnessing synergetic effects of improved salt-tolerant crops and varieties offer a possible approach to enhance productivity in these areas. Various approaches for improving and sustaining productivity in a saline environment include in situ conservation of rainwater in precisely leveled fields, and blending saline and fresh water to keep resultant salinity below threshold or to achieve its amelioration and precision irrigation technique with salty water at less salt-sensitive stages. Other productivity-improving measures involve soil and water management practices, methods of irrigation, its frequency and time of application or withholding of irrigation to maintain an environment favourable to crop production. Keywords: Saline water, Irrigation, Management practices, Conjunctive use

Introduction According to Central Ground Water Board (CGWB)1 , ground water levels have dropped (5-15 m) in many areas of India as a result of overexploitation of fresh water. Harmful effects of saline water irrigation are mainly associated with accumulation of salts in soil profile, reduced availability of water to plants, poor to delayed germination and slow growth rate 2 . Excessive salinity reduces plant growth primarily because it increases energy that must be expanded to acquire water from the soil of root zone and to make biochemical adjustments necessary to survive under stress. This energy is diverted from the processes that lead to growth and yield. Salinity may also affect plants by toxicity of specific salt, either through its effect on surface membrane to plant roots or in plant tissues or through its effect on intake or metabolism of essential nutrients. Long term use of saline water leads to breakdown of soil structure due to swelling and dispersion of clay particles. A thin crust formed at the surface of soil acts as a barrier to penetrating irrigation water to soil and to emergence of seedling3 . This study reviews adverse effects of saline/ sodic irrigation waters on growth and yield of crops and ∗Author for correspondence E-mail: [email protected]

ways to minimize such effects to some extent by adopting appropriate soil and crop management. Extent and Nature of Problem Brackish and saline waters4 are used for irrigation in almost all northwestern states of India [Rajasthan, Haryana, Punjab, Uttar Pradesh (UP), Gujarat, Maharashtra, Andhra Pradesh and Karnataka] having arid and semi-arid regions. Kerala, Tamil Nadu, partly Andhra Pradesh, Orissa, and West Bengal contain brackish and saline ground water as coastal states. States are following different classification of salinity of ground water for irrigation purposes with upper limit of salinity from 2.25 dSm-1 (UP) to 6.5 dSm-1 (Rajasthan) 6 . Extent of use of saline/alkali groundwater in different states in India is as follows5 : UP, 1.28; Rajasthan, 0.39; Punjab, 0.38; Haryana, 0.38; Andhra Pradesh, 0.24; Gujarat, 0.21; Madhya Pradesh, 0.20; and Karnataka, 0.07 M ha m a-1 (million ha m per annum). In ground water quality map of India 6 , ground water quality zones include good water, saline water, high sodium adsorption ratio (SAR) saline water and alkali water (Table 1). Though large spatial variations are encountered at small intervals, well waters (32-84%) in India have been rated to be poor in quality. High salinity ground waters largely occur in arid parts of north-western states of India (Rajasthan, Gujarat, Haryana and parts of Punjab). Alkali waters are found

JANGIR & YADAV : SALINE IRRIGATION WATER FOR ENHANCING CROP PRODUCTIVITY

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Table 1—Classification of water quality6 Water quality A) Good B) Saline water Marginally saline Saline High SAR saline C) Alkaline water Marginally alkaline Alkaline Highly alkaline

ECiw dSm-1 4

75% compared to conventional surface irrigation techniques. Saline water with high EC (up to 15 dSm-1) could be used to grow salt sensitive vegetable crops as follows12 : cauliflower, 15.0; brinjal, 9.8; cabbage, 9.7; water melon & musk melon, 9.0; tomato, 5.7; grapes, 4.0; and ridge gourd, 3.2 dSm-1. Conjunctive Use of Saline and Fresh Water

Conjunctive use is planned and practiced to mitigate effect of the shortage in canal water supplies, to alleviate problems of high water table and salinity resulting from introduction of canal irrigation, and to facilitate use of poor quality water that cannot otherwise be used without appropriate dilution and to minimize drainage water disposal problem13 . Blending of saline water with fresh water and cyclic irrigation schedule is also recommended for maximum returns with following alternatives: Alternative I— By mixing both waters into a common channel before applying to the field. Flow of both sources

is regulated to achieve desired permissible quality in common channel. Final quality in terms of salinity (ECiw dSm-1), SAR, RSC etc may be decided as per the nature of crop, soil and climatic parameters. Proportion of both the sources and their quality in terms of EC, SAR, RSC or individual cations/anions are related to ultimate mixed quality as EC or any parameter of mixed water = (Fraction of fresh water x Value of EC or any parameter of fresh water) + (Fraction of saline water x Value of EC or any parameter of saline water). Based on this relationship, any quality parameter as well as fraction of any of the sources may be worked out; Alternative II— Irrigation through both the sources may be given separately in cyclic fashion. Good quality water should be used for early irrigation coinciding with germination & tillering stages and saline water at later growth stages of grain filling & ripening. Salt sensitive and salt tolerant crops may be grown in rotation such as vegetable crops and winter crops (wheat or mustard) in a rotation irrigated with fresh and saline water, respectively; and Alternative III— In canal command areas, it is more advantageous to use groundwater of marginal quality during canal closure period. It will mitigate menace of rising water table and problem of waterlogged areas. Mixing of these waters for irrigation should be done in such a way that EC of mixed water does not exceed 3.75 dSm-1 for groundnut and 5.0 dSm-1 for wheat in light textured soils 14 . Blending and cyclic application of saline water with canal water in appropriate proportion sustained pearl millet and wheat yields (Table 3). Crop Management Selection of Crops and Varieties

Crops vary in their salinity and alkali tolerance behaviour15 (Table 4). Cereals are more tolerant to salinity as compared to pulses. Vegetable crops vary in tolerance from low (beans, potato and onion) to moderately high (cauliflower, spinach, radish, sugarbeet). Varietal difference among crops may cause strong differences

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Table 3—Effect of blending and cyclic application on grain yield of pearl millet and wheat 14 Pearl millet, q ha-1

Treatments Cyclic modes All canal water (CW) All saline water (SW) 1CW-Rest saline water (RSW) 1 CW-1SW 2 CW-1SW 1 SW-1CW Mixing mode Mixing SW & CW (1:2) Mixing SW & CW (2:1) CD 5%

Wheat, q ha-1

1997

1998

Mean

1997

1998

Mean

8.79 4.54 6.80 8.61 8.25 6.37

9.50 2.64 5.44 7.50 7.91 4.69

9.15 3.54 6.12 8.06 8.08 5.53

14.92 10.22 11.92 12.78 13.19 11.10

19.20 4.10 15.08 13.80 14.60 9.20

17.05 7.16 11.06 13.29 13.90 10.15

7.20 6.40 1.49

6.20 4.44 0.57

6.70 5.42 1.13

12.64 10.69 2.28

11.00 10.80 2.40

11.82 10.25 2.34

Table 4—Promising cultivars for saline and alkali irrigation waters15 Crop Wheat Pearl millet Mustard Cotton Sorghum Barley

Saline irrigation Raj 2325, Raj 2560, Raj 3077, WH 157 MH 269, 331, 427, HHB-60 CS 416, CS 330-1, Pusa Bold DHY 286, CPD 404, G 17060, GA, JK 276-10-5, GDH 9 SPV-475, 881, 678, 669, CSH 11 Ratna, RL 345, RD 103, 137, K169

regarding salt tolerance among varieties and root stocks of fruit trees and vine crops. Tolerant plants require multiple adaptations to enable them to grow in saline environments. Salt tolerance in plants is a polygenetic trait controlled by genes that synthesize enzymes responsible for a variety of biochemical and physiological processes. Genetic variation in salt tolerance does exist within and among plant species. Using DNA-based technology, markers may be a valuable means of assisting in development of salt tolerance in plants. Molecular biological approaches may be helpful for enhancing salt tolerance16 . Crop Growth Stages

Under irrigation with saline water or in saline soils, good emergence of seedlings with shortest delay is of primary importance for crop development. To ensure proper crop management at sensitive growth stages, germinating seeds should receive good quality water, especially if plants are sensitive and, in the case of lack of fresh water, only for tolerant and semi- tolerant plants, fair seed germination can be obtained9 by using saline water (EC < 4 dSm-1). If crops are sensitive during specific periods, it could be beneficial to lower soil salinity in upper part of root zone with the highest root density

Alkali irrigation KRL 1-4, Raj 3077, H11077, WH 157 MH 1269, 280, 427, HHB 392 CS 1, 52, Varuna, DIRA 336 HY 6, Sarvottam, LRA 5166 SPV 475, 1010, CSH 1, 11, 14 DL 4, 106, 120, DHS 12

by applying fresh water during sensitive periods, if such water is available to farmer17 . Cultural Practices

Adequate drainage and leaching to control salinity within the tolerances of crops are the most appropriate management practices for long term salinity control. Seed treatment, land smoothening and grading, plant population and seed placement and fertilization are important short term cultural practices, highly related to crop management. Such cultural practices can have profound effect upon germination, early seedling growth and ultimately on crop yield. Seed bed shape and seed location should be managed to minimize high salt effects. For soils irrigated with saline water, slopping beds are the best where seedling can be safely established on slope below the zone of salt accumulation18 . Managing Soil under Saline Irrigation Tillage

Tillage is usually carried out for fine seedbed preparation for improving root penetration, soil permeability improvement for facilitating leaching of salts, to break up surface crusts and to improve soil aeration & water infiltration. If tillage is improperly executed, it might form a plough layer or bring a salty layer closer to

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the surface. Sodic soils are especially subject to pudding and crusting; they should be tilled carefully and wet soil conditions be avoided. Deep Ploughing

In sodic soils, deep ploughing should be carried out after removing and reclaiming sodicity, otherwise it will cause complete disturbances and collapse of the soil structure. Deep ploughing (60 cm) loosens aggregates, improves physical condition of these layers, increases soil-water storage capacity and helps to control salt accumulation when using saline water for irrigation. Crop yields can be markedly improved by ploughing to this depth every 3 or 4 year19 . Chemical Soil Amendments and their Quantities

Unlike saline soil water, alkali soil water responds to chemical amendment materials that directly supply soluble calcium for replacement of exchangeable sodium. Choice of amendment and quantity required for reclamation depends on physico-chemical properties of soil, amount of exchangeable sodium to be replaced, desired rate of improvement, quality and quantity of water available for leaching and amendment cost. Gypsum by far is the most common indigenous amendment for sodic soil reclamation when using saline water with a high SAR value for irrigation. Addition of gypsum (either to soil or water) can often help appreciably in avoiding or alleviating problems of reduced infiltration rate and hydraulic conductivity. It also decreases SAR of irrigation water if added in irrigation system. Other amendments are pyrite and elemental sulphur. Organic Manures and Mulching

Incorporating organic matter into soil has beneficial effects of soils irrigated with saline water with high SAR and on saline sodic soils. It improves soil permeability and releases carbon dioxide and certain organic acids during decomposition. This also helps in lowering soil pH, releasing calcium by solubilization of CaCO3 , and other minerals, thereby increasing ECe and replacement of exchangeable Na by Ca and Mg, which lowers ESP. When using saline water, where concentration of soluble salts in soil is expected to be high in the surface, mulching can considerably help to leach salts, reduce ESP and thus facilitate production of tolerant crops. Mulching to reduce evaporation losses will also decrease opportunity for soil salinization.

Mineral Fertilizers

Benefits expected from using soil management measures to facilitate safe use of saline water for irrigation will not be realized unless adequate, but not excessive, plant nutrients are applied as fertilizers. Level of salinity may itself be altered by excess fertilizer application as mineral fertilizers are for the most part soluble salts. Type of fertilizer applied, when using saline water for irrigation, should preferably be acid and contain Ca rather than Na taking into consideration the complementary anions present. Timing and placement of mineral fertilizers are important and unless properly applied they may contribute to or cause a salinity problem. Conclusions and Research Priorities for Saline Water Management Adverse effect of saline irrigation water on crops and soils may be minimized if proper diagnosis of the resources is done and conjunctive management strategy is evolved on sustainable basis. Saline/ alkaline water has been successfully used to augment irrigation supplies and helps to raise water productivity. Recent research developments on salt tolerance of various crops, water, soil and crop management, irrigation and drainage methods will enhance and increase its potential use for irrigation. There is need to evolve integrated management of water of different qualities at the level of farm, irrigation system and drainage basins for increasing agriculture productivity, achieving optimal water use efficiency, and sustaining long-term production potential of land and water resources. Conjunctive use need be developed of saline groundwater and surface water (canal) module for different crops of the region to aid in lowering water table elevations, hence to reduce the need for drainage and its disposal and to conserve water. Operational research projects need to be established in saline groundwater areas on low volume and localized water application methods (sprinklers, drip and earthen pitchers). Mechanism must be available for coordinating research work and to utilize effectively research findings under farmers’ participatory research mode. References 1 2

3

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