Effects Of Plant Density And Nitrogen Rate On Yield And Nitrogen Utilization Of Summer Maize In Hebei Plain

The experiment was conducted at the Xinji Experimental Station of Hebei Agricultural University from June to October 2018.The tested corn variety was 370,with 67500(D1),75000(D2)and 82500(D3)strains/hm~2.Planting density and 0(N0),120(N120),180(N180),240(N240)And nitrogen application rates of 300(N300)kg N/hm~2 were used to study the effects of different planting densities and nitrogen application rates on summer maize yield,photosynthetic characteristics and nitrogen use,and economic benefit analysis was carried out for 15 combined treatments.The main findings are as follows:1.Reasonably increase the planting density,moderate nitrogen reduction improves the utilization rate of summer corn light energy.Increasing planting density,leaf area index and net photosynthetic rate increased significantly;appropriate nitrogen reduction increased leaf area index(LAI),net photosynthetic rate(Pn)and chlorophyll relative content(SPAD),improved population plant structure;in medium density(D2)Under the condition and nitrogen application rate of 180kg N/hm~2,the leaf area index(LAI),net photosynthetic rate(Pn)and relative chlorophyll content(SPAD)of maize increased significantly,and the utilization of light energy increased,which provided guarantee for grain yield formation.2.Reasonably increase planting density,moderate nitrogen reduction increased dry matter accumulation and grain yield of summer maize.With the increase of density,corn yield increased first and then decreased,and yield was highest at D2 density.Reduced nitrogen application reduced grain yield.When nitrogen application rate was reduced from300 kg N/hm~2 to 180 kg N/hm~2,the yield of summer maize decreased.Under medium-density conditions(D2)and nitrogen application rate of 180 kg N/hm~2,the yield was 12995.0 kg N/hm~2.3.Reasonably increase the planting density,moderate nitrogen reduction increased the nitrogen use efficiency of summer maize.The planting density was increased,and the nitrogen use efficiency(NUE)was significantly reduced under the same nitrogen application rate.Under medium nitrogen treatment(N180),the nitrogen use efficiency of maize was 73.57%,75.59%and 74.81%under low density D1,medium density D2 and high density D3 density,respectively.Under the conditions of medium-density(D2)and nitrogen treatment(N180),the nitrogen utilization rate of maize can be increased.4.Reasonably increase the planting density,moderate nitrogen reduction can optimize the economic and ecological benefits of corn.Increasing planting density and increasing nitrogen application rate,seed and nitrogen fertilizer input increased in summer corn production cost,and the cost-only rate of return increased first and then decreased.Under moderate nitrogen reduction conditions(N180),nitrogen utilization efficiency was the highest;under moderate-density conditions(75,000 plants/hm~2),the net yield of corn was significantly higher than that of high density and low density.From the above results and analysis,the following preliminary conclusions are drawn:the optimum planting density and nitrogen application rate for summer maize in Hebei Plain are 75000 plants/hm~2 and 180 kg N/hm~2 respectively.In this combination mode,high yield and high efficiency of summer maize can be achieved.