Technical standards of irrigation and drainage management in paddy field of water-saving and pollution-reduction with high yield

Reasonable irrigation and drainage management in paddy field of water-saving and pollution-reduction with high yield is an effective measure to alleviate water shortages, control agricultural non-point source pollution, and hence develop sustainable agriculture. Aims of this study were to determine effects of different water control programs on the responses of the fractional yield (FY), the rainwater utilization (RUM), the losses of ammonia nitrogen (NH 3 -N) and total phosphorus (TP). The relative optimized programs were gained by conducting the multi-objective entropy decision model at each stage. The results showed that the influence of plants flooding on paddy yield was more significant at milking stage than that at other stages. Compared to 5-days and 7-days flooding, FY of 10-days flooding was reduced by 3.41-12.07% and 1.59-5.80%, respectively. Flooding depth demonstrated greater impact on rice yield at milking stage than at other stages. Prolonging flooding period could increase RUM, and RUM values increased more rapidly in 5-7 days than those of 7-10 days. RUM of 10-days flooding was higher of 9.59-28.72% than that of 5-days, and 6.14-8.10% higher than that of 7 days. Prolonging flooding period could reduce the losses of NH 3 -N and TP. The losses amount of NH 3 -N and TP of 10-days flooding reduced by 31.4-81.8% and 112.4-500.4% compared to 5-days flooding, and by 18.1-81.3% and 53.7-254.4% compared to 7-days flooding. Leakage intensity at 2 and 4 mm/d had no significant effect on these indicators. Reasonable irrigation-drainage management was obtained by the multi-objective decision model, leakage intensity controlled at 4 mm/d; for tillering stage, flooding period lasted 5 days, flooding depth was 100 mm; for jointing-booting and milking stage, flooding period lasted 5 days, flooding depth was 250 mm; for heading-flowering stage, flooding period lasted 7 days, flooding depth was 200 mm.