Optimizing agricultural water and N managements based on their interactions on crop yield and environment

Agricultural water and nitrogen (N) interactions are the basis of optimizing irrigation and N managements for high crop yield and low environmental pollutions. In this paper, a field experiments with two irrigation levels and four N application rates (0, 100, 200, 300 kg N/ha per crop) in a wheat-maize double cropping system were conducted from 2000 to 2002. Soil N balance, crop yield and N use efficiency as influenced by the different water and N managements were analyzed. The results showed that crop yield maximized at 200 kg N/ha application rate, and wheat showed a higher N requirement than maize. High soil nitrate-N accumulation occurred at 200 kg N/ha or more N application rates, and showed greater N leaching potential for maize season than wheat season. High soil water level resulted in greater N leaching and deeper depths than the low soil water condition. Based on above results, about 150 kg N/ha for wheat and 100 kg N/ha for maize with low soil water level (60-75% field water capacity) were recommended for obtaining high crop yield, N use efficiency and low N loss to environments. This N application rates were much lower than the current N application rates practiced at local area.