Effects of Plant Density on Grain Yield and Nitrogen Use Efficiency of the Summer Maize with High Yield

Effects of plant density on grain yield and nitrogen use efficiency of summer maize under high yield condition are studied.Summer maize cultivar DH661 and CS11 were used for experimental materials.The results showed that the grain yield increased at first,then decreased with the increment of plant density.At the plant density of 120 000 plant/ha,the grain yield of DH661 was the highest,being 11 292 kg/ha.Nitrogen partial factor productivity(PFP) and the amount of total nitrogen accumulation(TNAA) in plant increased at first,then decreased,and reached the highest at the plant density of 120 000 plant/ha,37.64 kg/kg for nitrogen partial factor productivity,and the amount of total nitrogen accumulation in plant among the plant density of 30 000 plant/ha to 105 000 plant/ha increased at first,then decreased.And with the density increase,the amount of total nitrogen accumulation in plant increased again.Nitrogen utilization efficiency(NUE) was high under low density condition,with the plant density increasing,nitrogen utilization efficiency(NUE) increased at first,then decreased.Nitrogen harvest index(NHI) increased at first,then decreased with the density increasing,and reached the highest at the plant density of 120 000 plant/ha.As a result,increasing the plant density could improve grain yield and nitrogen use efficiency.In conclusion,under this field experiment conditions,as far as grain yield and nitrogen use efficiency are concerned,the most optimal density are 75 000-105 000 plant/ha.