Effects Of Nitrogen Fertilizer Top-Dressing Ratio And Lanting Density On Grain Yield Of Soybean

Soybean is an important oil crop in China.Soybean production depends on three factors,cultivar,environment and cultivation measures.Cultivation measures are important factors affecting soybean yield and quality.Nitrogen fertilizer and density are important factors affecting soybean yield.In this study,field experiments were conducted to investigate the effects of nitrogen fertilizer top-dressing ratio and planting density on grain yield of soybean,and the main reasons for high yield soybean production were explained systematically from the perspectives of material production,carbon and nitrogen metabolism and oxidation metabolism.In addition,the suitable basal and top-dressing ratio of nitrogen fertilizer and planting density were proposed to provide technical support for soybean high yield cultivation.The main results are as follows:1.The nitrogen fertilizer top-dressing ratio and planting density had significant effects on grain yield of soybean.Compared with T1(basal and top-dressing ratio 3:7)and T3(basal and top-dressing ratio 7:3),T2(basal and top-dressing ratio 5:5)significantly increased the number of pods per plant and the 100 grains weight,resulted in increased grain yield of soybean.With the increase of density,the grain yield of Xudou25 increased first and then decreased,while the grain yield of Qihuang34 decreased gradually.With the increase of density,the number of plant per unit area of the two soybean cultivars increased significantly,while the number of pods per plant,the grain number per pod and the 100 grains weight decreased significantly,and the decreases of Xudou25 were smaller than that of Qihuang34,indicating that Xudou25 could compensate for the reduction of the number of pods per plant,the grain number per pod and the 100 grains weight by the increasing the number of plants per unit area,so as to improve the grain yield.Therefore,in field soybean production,the basal and top-dressing ratio of nitrogen fertilizer is 5:5,which is suitable for soybean nitrogen fertilizer management.For resistant varieties,higher-density planting(450,000 plants/hm2)should be adopted,while for non-resistant varieties,low-density planting(300,000 plants/hm2)should be adopted.2.The nitrogen fertilizer top-dressing ratio and planting density had significant effects on soybean growth,carbon and nitrogen metabolism and oxidation metabolism.Compared with T1 and T3,T2 increased the biomass and dry matter accumulation of different organs at 5 days after anthesis,which was beneficial to improve grain yield of soybean.With the increase of density,Xudou25 increased the biomass and dry matter accumulation of different organs at 5 days after anthesis stage,while Qihuang34 showed the opposite trend,indicating that Xudou25 could maintain a better growth status under high density conditions.Moreover,the soluble protein content and chlorophyll content of leaves at 5 days after anthesis stage of soybean were improved under the treatment of T2,which was conducive to enhancing the photosynthetic capacity of soybean after anthesis.With the increase of density,Xudou25 increased the soluble protein content and chlorophyll content of leaves at 5 days after anthesis stage of soybean,while Qihuang34 showed an opposite trend,indicating that Xudou25 could maintain a higher photosynthetic capacity under high density conditions.In addition,T2 also increased the CAT,SOD,APX and GR activity of leaves at 5 days after anthesis stage,while reduced the O2-production rate and H2O2 and MDA content,which helped to delay the leaf senescence,and was conducive to maintain higher photosynthetic capacity after anthesis.With the increase of density,Xudou25 increased the CAT,SOD,APX and GR activity of leaves at 5 days after anthesis stage,while reduced the O2-production rate and H2O2 and MDA content,while Qihuang34 showed the opposite trend,indicating that Xudou25 could delay the leaf senescence of soybean under high density conditions.Therefore,keeping the good growth status of soybean,maintaining the higher photosynthetic capacity of leaves,and delaying leaf senescence are important reasons for the high yield of soybean.