Effects of Different Fertilizations on Soil Nitrate-N Distribution and Accumulation under Winter Wheat Summer Maize Cropping System

In order to improve the economic efficiency of nitrogen and reduce agricultural pollution,a field experiment was conducted to investigate the effects of different fertilizations on soil nitrate N distribution and accumulation,yields and fertilizer-nitrogen use efficiency under winter wheat summer maize cropping system in the Ziya River Basin.The results showed that the distribution and accumulation of the soil inorganic nitrogen was mainly nitrate N after wheat-maize rotation cycle.The soil nitrate content increased With the increasing nitrogen fertilization.The nitrate N in 0-40 cm depth of soil of conventional fertilization was significantly higher than the optimal fertilization and control treatments at corn harvesting.Compared with conventional fertilization,the residual nitrate N in 0-1.2 m depth of optimized fertilization,optimized fertilizer+organic fertilizer,optimized fertilization+straw,slow controlled fertilizer+organic fertilizer decreased 43.55%,26.53%,40.82% and 42.89%,28.96%,38.28%,32.52% respectively.The yields of winter wheat summer maize increased slightly.The optimized fertilizations significantly increased fertilizer-nitrogen use efficiency of winter wheat and summer corn,which increases 18.94%-51.20% in winter wheat season,and 13.77%-43.68% in summer corn season.Compared with conventional fertilization,optimized fertilization and controlled-release nitrogen fertilizer measures improved economic and environmental benefits significantly.The nitrogen fertilization measures were recommended.