Improving Water Productivity of Wheat-Based Cropping Systems in South Asia for Sustained Productivity

Serious water deficits are threatening agricultural sustainability in many regions of the South Asia (SA). While the increase in crop production of irrigated rice wheat system in SA has been impressive since the 1970s, the low water productivity (WP) has led to the depletion of surface water and groundwaters. In this chapter we have discussed the availability of water resources in SA, identified the positive effects of soil and water management and crop genetic improvement on WP, and then described knowledge gaps and research priorities to further improve the WP with special emphasis on Wheat-based cropping systems in irrigated and rainfed regions of SA. A single approach would not be able to tackle the forthcoming challenge of producing more food and fiber with limited or even reduced available water. Integrating irrigation water-saving techniques (water-saving irrigation methods, deficit irrigation, modernization of irrigation system, etc.) with agronomic and soil manipulations viz., optimum irrigation scheduling, direct-seeded rice, alternate wetting and drying in puddle transplanted rice, raised bed planting, crop diversification, conservation tillage, crop residue management, and conjunctive use of good quality (canal) water. Improved soil water management practices for rainfed regions include reducing runoff, rainwater harvesting and recycling, conserving rainwater in the root zone by reducing evaporation losses, and optimal nutrient management. The low WP in farmer's fields compared with well-managed experimental sites indicates the need for more efforts to transfer water-saving technologies to the farmers. In future we need to increase scientific understanding of the effects of agronomic management on WP across various soil and climate conditions; improve irrigation practices (timing and amounts) and methods (drip and sprinkler) based on real-time monitoring of water status in soil-crop systems; and maximize WP by managing water resources and allocation at regional scales in wheat-based cropping systems.