Optimizing Fertilizer Nitrogen for Winter Wheat Production in Yangtze River Region in China

Excessive nitrogen (N) application has been considered as one of the reasons for restricting yield increases in rice-wheat rotation system in the Yangtze River area. From 2007 to 2009, field experiments were conducted to evaluate the effects of optimized N management on grain yield, nitrogen use efficiency (NUE) and N surplus of winter wheat in Jianghan Plain (Hubei province, China). Results indicated that grain yield and crop N uptake of treatments with reducing fertilizer N (N-135(2) for the first year and N-120(3) for the second season) did not significantly reduce yield compared to farmers' practice (FP). Under the same amount of N application, three-time splitting improved grain yield and enhanced NUE as compared with two-time splitting. The optimized N treatment of N-135(2) and N-120(3) was observed with higher NUE parameters, i.e. recovery efficiency (REN), agronomic efficiency (AE(N)) and partial factor productivity (PFPN). Positive correlation between SPAD value and leaf N concentration provided the effective tool to evaluate N status during the growth season. The optimized N rate and top dressing frequency could reduce the residual N retained in the 0-20cm soil layer after harvest, which could reduce the possibility of soil N loss to the environment. This paper provides insights into N management strategy based on farmers' practices, which could be regarded as a guideline to improve agricultural management for wheat growth season.