Effects Of Planting Density And Nitrogen Application Rate On Yield And Mechanical Harvest Quality Of Early Spring Maize In Hubei Province

In the process of mechanization of maize,mechanized harvest is one of the most difficult problems.The mechanical harvest rate of corn in Hubei Province is still low due to many factors such as cultivation measures,cropping system and topographic conditions.By selecting early ripe maize varieties,it can prolong the time of dehydration of maize in the field and be more suitable for mechanized harvest without affecting the next crop.With the development of corn mechanization,the most suitable combination of dense nitrogen for high yield,high efficiency and machine income of spring corn in Hubei province needs to be discussed.The experiment selected the early spring maize variety Fengken 139 and set up four different nitrogen applications,including conventional nitrogen application(300 kg/hm~2,N300),25%nitrogen reduction(225 kg/hm~2,N225),50%nitrogen reduction(150 kg/hm~2,N150),and no nitrogen application(0 kg/hm~2,N0).as well as three densities,including 675,000/hm~2(D1),90,000/hm~2(D2),and11.25 million/hm~2(D3).The effects of different nitrogen combinations on maize growth,yield and economic efficiency,grain quality and machine harvest quality were investigated by conventional planting model(D1-N300).The main results were as follows:(1)The yield of maize per denitrogen combination was between 3.82t/hm~2and8.22t/hm~2,with net income between 0.31t/hm~2and 0.8t/hm~2.With the increase of nitrogen application rate,the yield and the net income start rendering increasing first and decreasing later.With the planting density increased,maize’s net income was significant increased.The yield and net yield of densification and nitrogen reduction treatment(D3-N225)increased by 46.0%and 122.22%,respectively,compared to the conventional model(D1-N300).(2)The light distribution of maize canopy was significantly affected by each denser nitrogen treatment.Increased planting density and nitrogen application rate can reduce the light transmittance and bottom layer.With the increase of density,LAI increased significantly in all periods,34.48%and 64.53%,respectively,in D2 and D3 treatment of spun wire compared to D1.With the increasing nitrogen application rate,maize LAI looked increasing trend first and decreasing trend later.Increasing density and reducing nitrogen fertilizer application(D3-N225)can increase of 77.62%in thread-spitting LAI compared to conventional farmer model(D1-N300).(3)During the whole filling period of maize,the grain dehydration rate was fast in the early stage and slow in the late stage,ranging from 0.69%to 1.90%/d overall.Moreover,the overall dehydration rate of D2 and D3 increased by 3.27%and 9.02%,respectively,compared to the conventional planting density D1.increasing density and nitrogen application rate,the contenting water of maize was decreased,and the water content of maize grains was between 24.17%and 27.03%.(4)With the increasing of density and nitrogen application rate,the loss rate and the impurity ratio of maize was decreased,and the fragmentation rate and heterozygous rate showed a trend of decreasing first and increasing later.The maize loss and fragmentation rate(D1-N300 was 5.02%higher than the national standard except for the conventional treatment of D1-N300 by farmers)reached the national standard(GBT21961-2008).The grain loss rate of densification and nitrogen reduction(D3-N225)was 1.53%,3.60%and0.84%,respectively,which was significantly lower than that of conventional model D1-N300.(5)Density and nitrogen application had no significant effect on the content of corn kernel protein and amino acid.Corn starch was between 63.17%and 75.09%with different densities,but there was no significant relationship with nitrogen application.Taken together,densification and nitrogen reduction(D3-N225)significantly improved dry matter accumulation,yield and net yield of maize compared to conventional farmer model(D1-N300).In the ripening stage,the empty stalk rate and inverting rate were lower than the national standard,and the grain fragmentation rate,heterosis rate and loss rate were lower.Combined with the results of this experiment,the optimum nitrogen application was 225 kg N/hm~2and the planting density was 12,500 plants/hm~2when early spring maize was selected for planting in hubei province.