Application of a rice growth and water balance model in an irrigated semi-arid subtropical environment

In order to enhance rice productivity in water-limited environments, there is a need to adopt water-saving practices. This study examines the applicability of the ORYZA2000 model in analyzing impact of water-related options on rice yield and water use for enhancing water productivity in irrigated environments of Punjab. Performance of the model was reasonably good as indicated by close matching between simulated harvest-time grain yield, biomass, and soil profile water use with measured data and trends of simulated water balance components for a range of soil and water management scenarios. Using long-term weather data, cumulative probability distribution of simulated grain yield and evapotranspiration (ET) showed that rice yield of late-transplanted (July 1) crop was comparable to that of early-transplanted (May 16) crop, and ET-based water productivity was greater in late-planted crop. Though ET-based water productivity with continuous submergence and 2-day interval regimes were comparable, water-input-based productivity was greater under 2-day interval regime. Increasing puddling intensity from P1 (puddling once) to P2 (puddling two times) and P4 (puddling four times) regimes had little effect on ET-based water productivity, but caused a substantial increase in water-input-based productivity.