Dry Matter and Nitrogen Accumulation as Affected by Nitrogen Fertilization and Seeding Rate in Winter Wheat

[Objective] Wheat grain yield mainly comes from the accumulation and redistribution of the material after anthesis, the objectives of this study were to assess the contribution of pre- and post-anthesis dry matter, fertilizer nitrogen (N) and soil native N assimilation to grain yield of winter wheat (Triticum aestivum L.). [Method] Field experiments were conducted to investigate the effects of seeding rates (150, 225 and 300 seeds m？2) at three N rates (0, 150, 225 kg N ha？1) on accumulation and remobilization of dry matter and N from different sources, and grain yield from 2008 to 2010. The experiment sites were located in the Middle and Lower Yangtze River Basin in China. A 15N micro-plot experiment was designed with the three seeding rates at rate of 150 and 225 kg N ha？1. [Results] The grain yield increased at higher N rate (225 kg N ha？1) and the optimum seeding rate (225 seeds m？2), and yield differences mainly depended on the number of spikes per unit area and were positively correlated with leaf area index. The higher N rate and seeding rate increased post-anthesis remobilisation amount of organic matter from leaves and stems and accumulation amount in grain that helped improve grain yield, but decreased remobilization efficiency and the contribution of remobilized dry matter to grain yield. Both post-anthesis N accumulation and remobilization of N from the different sources increased with increasing N rate and seeding rate. For fertilizer N, remobilization efficiency and the contribution of remobilized N to grain increased with increasing N rate and seeding rate, whereas for soil N, remobilization efficiency and contribution of N remobilization to grain N (CNRG) decreased. Fertilizer N remobilized to grain more easily than soil N, and top-dressed N remobilized to grain more easily than basal N. The correlation showed increasing remobilization of fertilizer N and post-anthesis accumulation of soil N were beneficial to improving grain yield. [Conclusion] In conclusion, for higher grain yield and nitrogen recovery, combining N fertilization at 225 kg N ha？1 with seeding rate at 225 seeds m？2 was recommended to wheat management in the Middle and Lower Yangtze River Basin