Analysing Dry-Seeded Rice Responses to Planting Time and Irrigation Regimes in a Subtropical Environment Using ORYZA2000 Model

Abstract

Irrigated rice is a luxurious consumer of water. Dry-seeded rice culture is an option that saves water, but may entail loss in crop yield implying a trade-off of productivity and water conservation. This study evaluates the water balance and productivity response of dry-seeded rice to management interventions using ORYZA2000 model. The database was generated from field studies involving combinations of planting dates and irrigation regimes. The performance of the model in simulating phenology, biomass, water use and yield was reasonable within the experimental conditions. The normalized root mean square of deviation (RMSDn) for simulated and measured harvest-time biomass and grain yield was 12 and 16%, while RMSDn for progressive soil water content and water use was less than 10%. Scenario analysis using historical weather data showed that rice planted on June 16 had minimum variance in potential yield (5.4%) compared to earlier (June 1) or later (July 1) planting. The evapotranspiration (ET)-based water productivity (WPET) was greater for June 16 and July 1 than June 1 planting. Loss of yield and WPET with reduction in irrigation frequency were least on June 16 rice implying this as optimal planting time of rice in the study region.