Strategies for managing saline/alkali waters for sustainable agricultural production in South Asia

https://doi.org/10.1016/j.agwat.2005.04.019Get rights and content

Abstract

Increasing the productivity of water and making safe use of poor quality waters in agriculture will play a vital role in easing competition for scarce water resources, prevention of environmental degradation and provision of food security. Driven by the pressure to produce more, even the saline and alkali waters are being increasingly diverted to irrigated agriculture. Development of salinity, sodicity and toxicity problems in soils not only reduces crop productivity and quality but also limit the choice of crops. There are two major approaches to improving and sustaining productivity in a saline environment: modifying the environment to suit the plant and modifying the plant to suit the environment, but the former has been tried more extensively. The available options are mediated through the management of crops/sequences, irrigation water, chemical/amendments and other cultural practices but all must be integrated as per the site specific needs and achieving higher yields on sustainable basis. Some important interventions include appropriate crop/variety selection, blending saline/alkali and fresh water to keep the resultant salinity below threshold, or their cyclic application by scheduling irrigation with salty water at less salt sensitive stages. At the farm/irrigation system level, policy measures like re-allocation of water to higher value crops and those with limited irrigation requirement, spatial re-allocation and transfer of water, adopting policies that favor development of water markets and adequate utilization of groundwater can help in improving water productivity in saline environments. The other viable options include salinity tolerant agro-forestry systems and bio-saline agriculture. Besides technological advances, peoples’ participation and favorable water use and allocation policies need to be put in place for sustainable use of saline/alkali waters.

Introduction

Development of surface and groundwater resources for irrigation plays a vital role in the production of food and fiber. Large parts of Australia, the Indian sub-continent, China, countries in the middle east, small parts in the Americas and Europe and significant regions in north Africa are generally water deficient (Seckler et al., 1998) and the situation may further aggravate due to enhanced biotic pressure. Areas characterized by water scarcity are also usually underlain by aquifers of poor quality (Sharma, 2003). Nevertheless, driven by the pressure to produce more, even the brackish ground waters are being increasingly diverted to irrigated agriculture. The areas underlain with saline groundwater include the areas with high aridity, with high water table and water logged conditions and in the vicinity of seawater as in coastal regions, while the alkali waters exist generally in areas with annual rainfall of 500–700 mm. Large amounts of drainage effluents of poor quality are expected to be produced in areas covered with sub-surface/surface drainage system. Many more areas with good-quality aquifers are endangered with contamination, as a consequence of excessive withdrawals of groundwater (Shah and Deb Roy, 2002). Indiscriminate use of poor quality waters in the absence of proper soil-water-crop management strategies poses grave risks to soil health and environment (Bouwer, 2000, Minhas and Bajwa, 2001). Development of salinity, sodicity and toxicity problems in soils not only reduces crop productivity and quality but limit the choice of crops. Saline water management signifies those methods, systems and techniques of water conservation, remediation, development, application, use and removal that provide a socially and environmentally favorable level of water regime to agricultural production system at the least economic cost (Hillel, 2000). Possibilities have now emerged to safely use waters otherwise designated unfit if the characteristics of water, soil and intended usages are known (Tyagi and Sharma, 2000, Qadir et al., 2003). This has led to replacement of too conservative water quality standards with site specific guidelines, where factors like soil texture, rainfall and crop tolerance have been given due consideration (Minhas and Gupta, 1992). This paper briefly outlines the crop, root zone, and farm and irrigation system level strategies available for alleviating hazards of salty waters.

Section snippets

Management of saline and alkali waters

There are two major approaches to improving and sustaining productivity in a saline environment: modifying the environment to suit the plant and modifying the plant to suit the environment. Both these approaches have been used, either singly or in combination (Minhas, 1996), but the former has been used more extensively because it facilitates the use of alternative production inputs. The development of management options requires the analysis of sensitivity parameters that affect interactions

Sustainable productivity at irrigation system level

In most of the irrigation systems, large differences in supply between the head and tail reaches were observed. The problem gets compounded if the canal water supplies are only sufficient to meet 30–50% of the seasonal crop water requirement. The water inadequacies at the tail end are further complicated by the progressive decrease in groundwater quality from head to tail reaches. In a study conducted by IWMI and Central Soil Salinity Research Institute, Karnal, India, at Kaithal Circle in

Alternative land use systems

In some cases it is neither feasible nor economical to use highly saline waters for crop production, especially on lands that are already degraded. Best land use under such situations is to retire such areas to permanent vegetation. Conventional planting methods result in poor survival percentage under saline environments. To establish good plantations and to improve biomass production from such lands, ‘SPFIM’ (sub-surface planting and furrow irrigation method) system of planting has been

Conclusions

Saline/alkali waters constitute an important resource for agricultural production in water scarce regions. But indiscriminate use of poor quality water in the absence of proper soil-water-crop management practices may lead to degraded soils and environment. Researchers and practitioners have tried either to modify the plant to suit the saline environment or modify the environment to suit the plant. Past research has mainly focused on root zone salinity management with little consideration given

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