Effects Of Different Planting Density And Nitrogen Rate On Yield And Nitrogen Utilization Of Spring Maize In Hubei Province

With the development of mechanized production of maize,density tolerant varieties are gradually popularized and applied in production.At present,the planting density of Maize in Hubei Province is low,the amount of nitrogen application is too high,and the dense nitrogen combination is unreasonable.Therefore,exploring a reasonable dense nitrogen combination suitable for Maize in Hubei Province can provide a scientific basis for high-yield,high-efficiency,green production of Spring Maize in Hubei Province.This experiment was conducted to study the yield,nitrogen absorption and utilization of early spring maize variety Fengken 139 under different nitrogen density combinations in Qujialing,Jingmen,Hubei province from 2020 to2021.Split plot design was adopted in the experiment,and nitrogen application rate was the main zone,including conventional nitrogen application(N300,300 kg N/hm~2),25%reduction(N225,225 kg N/hm~2),50%reduction(N150,150 kg N/hm~2),and no nitrogen application(N0,0 kg N/hm~2).The density was subregion,including 67,500plant/hm~2(D1),9,000,000 plants/hm~2(D2)and 112,500 plants/hm~2(D3).Conventional nitrogen application rate and conventional planting density(N300-D1)were used as control.The main results were as follows:(4)Reducing nitrogen 25%on the basis of conventional nitrogen application rate can significantly reduce soil nitrogen residue by 34%and apparent nitrogen loss by31%;at the same time,densification(D3)will also be significantly reduced on the basis of conventional planting density(D1)14%nitrogen apparent loss.Combining the effects of nitrogen reduction and increasing density,nitrogen reduction 25%(N225)combined with increasing density(D3)can significantly reduce soil nitrogen residues by 25%and apparent nitrogen loss by 46%compared with the conventional model N300-D1.(2)Within the nitrogen application rate of 0-300 kg N/hm~2,with the increase of nitrogen application rate,the yield first increased and then slowed down.When the nitrogen application rate exceeded 225 kg N/hm~2,the yield no longer increased significantly,and the number of grains per panicle and 100 grain weight increased with the increase of nitrogen application rate;Within the density of 67500 plants/hm~2-112500 plants/hm~2,the yield of D3 treatment increased significantly by 20%and 38%compared with D1 in two years.Grains per ear and 100 grain weight decreased with the increase of planting density.In all dense nitrogen treatments in the two years,the highest yield appeared in nitrogen reduction and densification N225-D3 treatment,which were 11.68 t/hm~2 and 8.16 t/hm~2,significantly increased by 23%and 46%compared with N300-D1.(3)The accumulation of dry matter and nitrogen increased with the increase of nitrogen application,however,when the nitrogen application rate exceeds 225 kg N/hm~2;the accumulation of dry matter and nitrogen no longer increased significantly.The dry matter and nitrogen accumulation increased with the increase of planting density.The dry matter accumulation of D3 treatment in two years increased significantly by 32%and 54%compared with D1.In two years,the dry matter accumulation of N225-D3 treatment in mature stage was significantly increased by 25%and 46%compared with N300-D1,and the nitrogen accumulation was significantly increased by 55%and 46%.Reducing nitrogen fertilizer and increasing density(N225-D3)treatment could improve the dry matter and nitrogen accumulation of maize.(4)Excessive nitrogen application reduced the nitrogen transport efficiency,and the nitrogen transport efficiency of N225 was significantly increased by 75%and 80%compared with that of N300.Both Reducing nitrogen fertilizer and increasing density can significantly increase the nitrogen use efficiency of maize.Compared with the conventional nitrogen application rate,the nitrogen use efficiency of nitrogen reduction25%can be significantly increased by 20%and 5%,and the nitrogen fertilizer agronomic use efficiency can be significantly increased28%,the partial productivity of nitrogen fertilizer increased significantly by 31%and 32%;also compared with the conventional planting density,increasing the planting density D3 nitrogen fertilizer utilization rate can significantly increase by 164%and 47%,nitrogen fertilizer agronomic utilization rate significantly increased by 78%and 66%,nitrogen fertilizer The partial productivity increased significantly by 24%and 40%;therefore,the comprehensive nitrogen reduction and densification benefits,nitrogen reduction by 25%(N225)and increasing density(D3)combined with nitrogen fertilizer utilization can be significantly improved compared with the conventional planting mode(N300-D1)266%and 41%;nitrogen fertilizer agronomic efficiency increased significantly by 116%and145%,nitrogen partial productivity increased significantly by 64%and 95%.(5)With the advancement of the maize growth period,the critical nitrogen concentration of the stem gradually decreased,and the critical nitrogen concentration of the leaf increased first and then decreased,and both decreased significantly in the later growth period.When the planting density is increased,the critical nitrogen concentration in the stem and leaf parts increases during the growth period,and the critical nitrogen concentration in the leaf part is generally higher than that in the stem part.Nitrogen application can improve the nitrogen nutrition status of the stems and leaves of maize.With the increase of nitrogen application rate,the nitrogen application rate in n225 and N300 treatment basically meets the nitrogen demand of maize stem and leaf growth,the planting density was increased,the nitrogen nutrient index of maize decreased significantly in the later stage of growth,and the increasing density led to an increase in the nitrogen demand of corn stems and leaves in the later stage.In summary,the nitrogen reduction and increasing density optimization was carried out on the nitrogen application rate of 300 kg N/hm~2 and the planting density of67,500 plants/hm~2 in the conventional planting mode,the nitrogen application rate was reduced to 225 kg N/hm~2 and the planting density was increased to 112,500 plants/hm~2.Obtain higher corn yield,improve dry matter accumulation and nitrogen absorption and utilization.