Effect of Nitrogen Application on Translocation of Dry Matter and Nitrogen, and Nitrogen Balance in Winter Wheat under Rice-wheat Rotation

Field experiments were conducted to investigate the effects of nitrogen(N) rates(N0,N150,N225 and N300) and topdressing ratios(N1/9,N3/7,N5/5 and N7/3) on post-anthesis dry matter and N assimilation and translocation,using wheat cultivars with different grain protein contents,i.e.Ningmai 9(low protein) and Yumai 34(high protein).The results showed that grain yield and protein content increased with increasing of an appropriate N rate and topdressing ratio.With the increment of N rate and topdresssing ratio appropriatly,dry matter translocation amount increased.However,dry matter transfer efficiency and the contribution of dry matter translocation to grain yield decreased when more N fertilizer and topdressing ratio was applied.N tranlocation amount increased with an increase of N rate and an appropriate topdressing ratio,but N translocation efficiency and the contribution of N translocation to grain N decreased with the increment of N rate and topdressing ratio.The correlation analysis indicated that increasing post-anthesis dry matter accumulation was favorable for improving grain yield and increasing N translocation from vegetative organs to grain was favorable for improving grain protein content.High N rate and basal ratio increased N loss amount and decreased N utilization.It is suggested that the N rate was 225 kg·hm-2,topdressing ratio was not more than 50% for Ningmai 9,and 50%～70% for Yumai 34 had a better grain yield,protein content and N utilization efficiency,reduced N loss.