Irrigation scheduling of paddy rice using short-term weather forecast data

Abstract

Better use of rainfall is an essential strategy to save irrigation water for paddy rice. Since unnecessary irrigation is usually applied to field without considering the possible rainfall after irrigation, weather forecast (e.g., rainfall) can be used to potentially save irrigation water. In this study, the rainfall event mainly focused on the total rainfall in consecutive 3 days within rice growth period rather than the daily rainfall. Based on that, three rain levels were redefined for irrigation decision-making. By incorporating the possible rain level of the first 3 days in weather forecast horizon, a new method based on simple decision rule was proposed and evaluated for irrigation scheduling of paddy rice over a wide range of climate conditions in China. The results indicated that, the occurrence probability of each rain level in next 3 days can be clearly recognized, and their forecasting performance was much better than that of daily rain events. Comparing to the conventional irrigation, the newly proposed irrigation scheduling method can further save irrigation water (about 0 − 100 mm) and reduce drainage (about 0 − 60 mm) without significant yield loss (< 1%). The results also showed that, the efficiency of water saving and drainage reduction had a certain correlation with the total rainfall and the daily rainfall distribution during rice growth period. Moreover, about 1 − 3 extra irrigations were needed in this new irrigation scheduling method due to great temp-spatial variation of rainfall distributions and imperfect weather forecasts. Nevertheless, the newly proposed irrigation scheduling method incorporated with weather forecast is suggested to apply in irrigation practice for its simplicity and effectiveness.