Test study on water saving and environmental effects of rain-catching and controlled irrigation of rice

The following parameters were investigated in a two-year farm experiments with materials of hybrid rice cultivar “Kyou 818”, which were Rainfall use efficiency(RUE), irrigation and drainage quota, loss load of nitrogen and phosphorus, grain yield and irrigation water production efficiency(IWPE) under rain-catching and controlled irrigation(RCCI), continuous flooding irrigation (CFI) and shallow frequent irrigation(SFI). Comparative analysis results of different irrigation models were presented to study the water saving, labor saving and environmental effects of RCCI. Results showed that comparing with CFI and SFI without reduction of grain yield, RCCI increased RUE by 3%-12% while it reduced irrigation quota and drainage quota by 15%-32% and 13%-68% respectively. RCCI decreased both irrigation times and drainage frequency by 1-3times. In addition, the loss load of nitrogen and phosphorus from surface drainage water declined 24%-78% and 40%-80%, respectively. However, if the rain-catching depth was excessively high under RCCI, it would cause a small cut of grain yield by about 3%-6%. The results above indicated that RCCI had advantages of water-saving, labor-saving and environment-protecting and it was suitable for rainy regions in South China.