Effects of Nitrogen Application Time on Carbon Assimilate and Nitrogen Translocation and Nitrogen Use Efficiency of Summer Maize

Aimed to reduce pollution of nitrogen fertilizer(NF)and heighten nitrogen use efficiency(NUE)in summer maize,effects of nitrogen application time(applied nitrogen in 3-leaf stage,applied nitrogen in 12-leaf stage,applied nitrogen in 3-leaf stage and 12-leaf stage)on carbon assimilate and nitrogen translocation and NUE were studied in 2007.The main results as follows,nitrogen application reduced the amounts and remobilization rate of per-anthesis stored assimilates and total amount of pre-anthesis stored assimilate,weakened the ability of per-anthesis stored assimilates re-transportation to grain.Nitrogen application reduced the amounts and remobilization rate of per-anthesis stored nitrogen,increased the content of nitrogen in grain.In treatments of three nitrogen application time,the NUE of treatment of applied nitrogen in 3leaf stage and 12-leaf stage was top,and increased 21.8 percent pionts and 22.8 persent points than the others,it improved the NUE of summer maize in the stage,and reduced the farm pollution by losing of nitrogen.