Effects of Nitrogen Managements on Canopy Structure and Nitrogen Absorption Utilization of Summer Maize

In order to explore the four nitrogen management patterns,the field experiment was conducted to analyze the effects of nitrogen management models on canopy structure and nitrogen fertilizer utilization of summer maize. The results showed that nitrogen fertilization significantly improved yield components and grain yield of maize.Under the same amount of nitrogen,to compare the treatment of dressing nitrogen both in the large trumpet stage and silking stage with that just in the large trumpet stage,grains per spike increased by 28.5,harvest index increased by 11.3%, yield increased by 101 kg/ha.LAI at the grain-filling stage significantly increased with N dressing at silking stage, and thus the high LAI was maintained and reached maximal value at filling stage.In addition,SPAD values of summer maize also increased with nitrogen application,especially with the combination of the base fertilizer and big trumpet fertilizer.Plant height,stem diameter and ear height were all improved with nitrogen dressing at silking stage.ANUE and PFP increased by 232.3%,60.9%,respectively,with low nitrogen application rate.Moreover,delaying of nitrogen application to silking stage,ANUE and PFP increased by 10.5%,1.3%,respectively.Nitrogen dressing at silking increased the nitrogen accumulation in vegetative organs of summer maize,while reduced nitrogen accumulation in grain,resulting in decrease of nitrogen harvest index.