Assessing the Impact of Climate on Actual Crop Water Use over Irrigated Rice and Rape in East China Plain over Four Decades

Abstract

Evapotranspiration (ET) is an important component of the water cycle at field, regional and global scales. This study used measured data from a 40-year (1970–2009) in the East China plain on Rape and Rice to analyze the impacts of climatic factors on actual crop water use and crop yield. The results showed that grass reference evapotranspiration (ET0, calculated by FAO Penmen Monteith method) was relatively constant from 1970 to 2009. Average seasonal crop water use was 250 mm and 154 mm for Rice and Rape, respectively, over the four decades. The seasonal decrease in crop water use was around 1.4 mm per season for Rice, and 0.08 mm per season for Rape. Average seasonal effective rain was 456 mm and 120 mm for Rice and Rape, respectively, over the four decades. The seasonal increase in effective rain was around 0.7 mm per season for Rice, and 0.03 mm per season for Rape. The result showed that over the four decades actual crop water use decrease much greater than the increase in effective rainfall. The results also showed that with new cultivars and improved management practices it was possible to further increase grain production without much increase in water use.