Effects of Planting Densities on Dry Matter and Nitrogen Accumulation and Grain Yield in Spring Maize

Effects of planting densities on dry matter and nitrogen accumulation and grain yield were studied in two high-yielding maize cultivars(Shaandan 609 and Zhengdan 958) with four planting densities,45 000(D1),60 000(D2),75 000(D3),90 000(D4) plants·hm-2.In the tested range of planting density,the yields of two cultivars increased with the increase of planting density,and the highest yield were obtained at planting density D4,with the yield of 13 660.5 and 13 452 kg·hm-2,respectively.Compared with the planting density D1,for Shaandan 609,the grain yields at the planting densities D2,D3,D4 were increased by 16.75%,28.74% and 35.34%,respectively;and for Zhengdan 958,increased by 16.38%,29.96%,and 37.06%,respectively.Regression analysis showed that the highest yield would be reached at the density of 102 380 plants·hm-2 for Shaandan 609 and 90 498 plants·hm-2 for Zhengdan 958.With the increase of planting density,the leaf area index(LAI) and percent of natural light interception increased significantly,while percent transmission of bottom decreased significantly.Population dry matters and accumulations,translocations,translocation rates,contribution rates of dry matter and accumulations,translocations,translocation rates,contribution rates of N nutrient in different organs increased with the increase of planting density.Accumulations and translocations of N nutrient had a remarkably negative correlation with the accumulation and translocation of dry matter in each organ;which suggested planting densities influenced accumulations and translocations of N nutrient through accumulation and translocation of dry matter.The results suggested that increasing planting density can enhance the photosynthetic area,increase effective light interception and increase accumulations and translocations of dry matter and N nutrient,thus improve the grain yield.