Influence of Nitrogen Topdressing Stage on Nitrogen Uptake,Translocation and Grain Yield of Wheat with Good Quality

[Objective] The study aimed to reveal nitrogen(N) using mechanism of wheat in different N topdressing stage.[Method] The influences of dressing N in different stages on N uptake,distribution, translocation and yield of wheat with good quality were studied by isotope tracing technique.[Result] Under the experimental condition,73.36%～78.58% of N absorbed by wheat was from soil and 21.42%～26.64% of that was from fertilizer.On the jointing and flagging stage,topdressing N fertilizer could promote the N absorption of plant,especially on fertilizer N and enhance distribution amounts and distribution proportion of N in ear organ during florescence and grain during mature stage,and promote shift of N in vegetative organs to grain after florescence.The 74.08%～80.28% of N in wheat grain was allocated and transported from vegetative N before florescence,and the contribution of vegetative organs to grain: leaf blade stem ear axis + glume leaf sheath root.Dressing N during suitable time increased grain number per ear,enhanced harvest index and output.[Conclusion]Topdressing N fertilizer in different stages had obvious regulation effect on the N metabolism,yield and quality of wheat.