Effects of Planting Density and Nitrogen Rate on Grain Yield, Dry Matter Accumulation and Nitrogen Utilizatio nEfficiency of High Yield Summ er Maize
The purpose of this research was to reveal the effects of planting density and different nitrogen rate on grain yield, dry matter accumulation and nitrogen utilization efficiency of high yield summer maize , and provide basisin theory and technique for further breaking through yield of summer maize .Selecting Tiantai 33as experiment material,the study was conducted with six nitrogen application levels (0, 180, 270, 360, 450 and 540 kg/hm2) and five planting densities (60 000, 67 500, 75 000, 82 500, 90 000 plants/hm2 ) .The results showed that within limits the increase of planting densities could significantly increase maize yield and total dry matter accumulation.Beyond one density ( 82 500 plants/hm2 ) conditions, the increase of maize yield slowed down or even slightly reduced.The amount of nitrogen transition, assimilating amount of nitrogen after anthesis, nitrogen <br> increase of nitrogen rate could significantly reduce the nitrogen partial factor productivity, total nitrogen accumulation, nitrogen agronomy efficiency, nitrogen utilizationefficiency and nitrogen harvest index were up after a decline.In conclusion, under this experimental field condition, the appropriate increase of planting density and nitrogen rate could greatly improve grain yield and nitrogen use efficiency.The most optimal planting density and nitrogen rate are 75 000 -90 000 plants /hm2, 360-450 kg/hm2, respectively, for higher grain yield and nitrogen use efficiency.
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