Effects of straw returning combined with nitrogen fertilizer application on yield of winter wheat and nitrogen regulation

Using the wheat cultivarZhoumai 23 asmaterial,there were 10 treatments thatwere coded asN0,N84,NI68,N252 and N336(standing for single nitrogen fertilizer at 0,84,168,252 kg·hm-2and 336 kg·hm-2,respectively),and S+N0,S+N84,S+NI68,S+N252 and S+N336(standing for 5 500 kg·hm-2straw returning combined with nitrogen fertilizer at the rates as above).The results showed that,comparedwith the single N treatments,the yield of wheat underS+N treatments showed a trend of decrease,but the difference between themwas insignificant statistically.Nitrogen fertilizer use efficiency underS+N treatmentswas 1.6%~9.1%higher than that of N treatments.Straw returning combined with an appropriate amount of nitrogen fertilizer tended to decrease N-requirement per 100 kg grain.In conclusion,strawreturning combinedwith nitrogen fertilizer application produced positive effects onwheatproduction,and 252~321 kg·hm-2was a suitable rate of nitrogen application forwinterwheat in the experimental area.