Evaluating Yield Response of Paddy Rice to Irrigation and Soil Management with Application of the AquaCrop Model

Abstract

Yield of lowland paddy rice (Oryza sativa L.) is sensitive to the water supply, which can be affected by irrigation management (i.e., irrigation method) and soil management (i.e., cropping history). The objective of this study is to analyze the responses of rice yield to the irrigation method and cropping history of a rice field by using the AquaCrop model. The field experiment was conducted in 2008 and 2009 with four treatments, i.e., two irrigation methods (continuous submergence vs. intermittent irrigation) and two different cropping history treatments (30 vs. 7 years of rice cropping). The model was calibrated in terms of soil water content, green canopy cover, aboveground dry biomass, and paddy rice yield. The validation of the model showed satisfactory simulation results for biomass and yield. The AquaCrop model proved to be robust and applicable for paddy rice under various irrigation methods and cropping histories, although it tended to underestimate the dry biomass at the earlier growth stage. The simulated rice yield was highly sensitive to the maximum canopy cover. The biomasses and yields in the seven-year (Y7) field were more sensitive to input data of climate and crop and soil parameters than in the 30-year (Y30) field, with an average sensitivity index of 9.5% vs. 2.9% for Y7 vs. Y30. In contrast, the average sensitivity index did not show an obvious difference for intermittent irrigation (II) and continuous submergence (CS), with an average sensitivity index of 6.6% vs. 5.9% for II vs. CS. Because the AquaCrop model was applied to the paddy rice crop for the first time and this research is site-specific, the model has to be further tested with different climate conditions, soil types, and crop varieties.