Effects of nitrogen rate and planting density on grain yield and nitrogen utilization efficiency of high yield summer maize

Two summer maize cultivars,DH661 and ZD958,were used as experiment materials to study the effects of different nitrogen rates(N 0 kg/ha,120 kg/ha,240 kg/ha and 360 kg/ha) and planting densities(60000 plant/ha,75000 plant/ha,and 90000 plant/ha) on yield and nitrogen use efficiency of summer maize under the field condition.The results show that compared with the 60000 plant/ha,the increase of nitrogen rate could increase the dry matter accumulation amount per plant,biomass,grain yield,total nitrogen accumulation,nitrogen transition rate and nitrogen transition efficiency of maize.The contribution proportion of nitrogen is increased with the increase of the nitrogen rate,while the nitrogen partial factor productivity,nitrogen agronomy efficiency and nitrogen recovery efficiency are decreased.In conclusion,under this experimental field condition,the increase of the nitrogen rate could improve grain yield,nitrogen use efficiency in higher planting density.As far as the grain yield and nitrogen efficiency are concerned,the most optimal plant density and nitrogen rate are both 90000 plant/ha and N 240-360 kg/ha,respectively.