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In the semi-arid tropics (SAT) farmers practice calendar-based irrigation scheduling, which generally results in over irrigation and poor water use efficiency. The lack of a simple decision tool to decide timing and quantity of water to be applied is a bottleneck. An Excel-based decision support system termed Water Impact Calculator (WIC) is developed using data collected at the ICRISAT, which were validated at three pilot sites on farmers' fields in Rajasthan, Gujarat and Telangana. Field studies were conducted under two land-form treatments (broad bed and furrow (BBF) and flat fields); and irrigation water was applied following two different methods (drip and flood). The data collected at micro-watershed at the ICRISAT and three other sites showed that WIC could be used under wide range of soil and rainfall conditions. WIC simulated soil moisture was comparable with the observed moisture data, which forms the basis of irrigation scheduling. The WIC-based water balance at these experimental sites showed that number and amount of irrigation could be reduced by 30-40% using WIC-based irrigation scheduling without compromising the crop yield. The WIC could be a potential tool for water resources planning and efficient management at the field and watershed scale in the SAT. [ABSTRACT FROM AUTHOR]

Large variability and uncertainty of rainfall are the main limiting factors for crop growth in rainfed agriculture. Agriculture water management interventions are considered as suitable adoption strategy to enhance crop yield, productivity and income in rainfed condition. Three-year experimental data collected at the International Crops Research Institute for the Semi- Arid Tropics, Patancheru, India are analysed to study the impact of in-situ interventions (tillage and crop residue) on field water balance and grain yield under the two different cropping systems (maize + chickpea sequential and maize/pigeon pea intercropping). One dimensional water balance model is calibrated to capture field hydrology (soil water, surface runoff). Weather data calibrated for 36 years showed that incorporating crop residues reduced surface runoff by 28% compared to control fields. However, the impact of tillage and residue treatment on soil water was not consistent throughout the growing period. Water productivity values for intercropping systems (WUE = 0.61 to 1.49 kg -3) were relatively higher compared to sequential cropping systems (WUE = 0.47 to 1.06 kg -3). Second crop in sequential cropping system often suffered from water stress that led to poor crop yield. However, a few rain events at the end of the monsoon period were beneficial to second crop. Simulation results indicated that the conservation agriculture could save up to 30% yield loss incurred due to water stress during deficit rainfall compared to conventional agricultural practices. [ABSTRACT FROM AUTHOR]