Effects Of Nitrogen Fertilizer And Planting Density On The Growth And Nutrient Absorption Of Different Varieties Of Maize

As one of the three major grain crops in China.Maize production and planting area accounted for 33.6%and 32.5%of the total grain production and planting area in China in 2016.However,the nutrient requirement of different types of high-yielding maize at present is still unclear.As a result,excessive fertilizer inputs in the maize production reduces the fertilizer utilization efficiency and the quality of grain and straw.Therefore,it is very important for maize sustainable development to coordinate the grain yield and nutrient balance of different types of maize.In this research,we measure the effect of nitrogen(N)application and planting density on grain yield,N dynamic accumulation,and grain quality of three different maizes(grain maize,fresh maize and silage maize).The aim of this study was 1)to measure the critical N application rate and planting density for grain yield,biomass,and N accumulation of three maize types;2)to clarify the effect of N application and planting density on N utilization efficiency and grain quality for three maize types.The main results are as following:The effect of N fertilization application on the grain yield of grain maize(YuDan30,ZhongDan808),fresh maize(YuNuo7,JingKenuo2000),silage maize(YuQingyu3,YaYu 8)showed that yield response to N application fitted to quadratic curve.Under the optimization of nitrogen fertilizer management,the grain yield of silage maize(average 12.6 t/hm~2)was higher than that of grain maize(average 10.3 t/hm~2)and fresh maize(7.53 t/hm~2).Meanwhile,the accumulation of dry matter of the total plant and different organs were highest for grain maize but the accumulation of dry matter for fresh maize was the lowest.The plant height,stem diameter and the chlorophyll content in the three maize types partly explained the difference of yield formation.Under the condition of high yield,the nitrogen application of silage maize was 381.8kg/hm~2 which was higher than grain maize(367.1 kg/hm~2)and fresh maize(357.8kg/hm~2).Nitrogen fertilization significantly increased the shoot nitrogen uptake and the nitrogen uptake of silage maize(174.1 kg/hm~2)higher than that of grain maize(159.6 kg/hm~2),fresh maize(48.68 kg/hm~2).The physiological utilization efficiency,nitrogen partial factor productivity(PFP_N),agronomic efficiency of maize decreased with increasing N application.Under the condition of optimized N application,physiological utilization efficiency of three types of maize was grain maize(69.3kg/kg)>fresh maize(61.9 kg/kg)>silage maize(37.6 kg/kg)and the agronomy efficiency was grain maize(26.05 kg/kg)>silage maize(16.45 kg/kg)>fresh maize(9.3 kg/kg).Increasing nitrogen application significantly improves silage maize grain starch concentration but had no effect on grain maize and fresh maize.The grain protein concentration was increasing with increased N application.In terms of maize varieties,the protein concentration in silage maize(8.1%)was higher than that in grain maize(7.21%),and fresh maize(3.8%).The interaction between planting density(40500,48000,55500,63000/hm~2)and N application showed that the optimal planting density for maxmum grain yield was55500 plants/hm~2 under the optimal N levels(270 kg/hm~2).In the optimal planting density,The orders of grain yield of the three maize types under the optimal planting sensity was silage maize(average 12.72 t/hm~2)>grain maize(average 10.76 t/hm~2)>fresh maize(average 7.55 t/hm~2).At the same time,the accumulation of dry matter of the total plant and organs for grain maize was the highest while the fresh maize was the lowest.Enhancing planting density significantly increased the nitrogen uptake by plant.In terms of N uptake in the different types of maize,N uptake of silage maize(175.7kg/hm~2)was higher than that of grain maize(162.8 kg/hm~2)and fresh maize(54.2kg/hm~2).The increase of planting density had no effect on maize starch content,protein concentration,and soluble sugar concentration.Under the optimal planting density,the starch concentration in fresh maize(73.16%)was higher than that in silage maize(73%)and grain maize(71.27%).In conclusion,an optimal N application(270 kg/hm~2)and planting density(55500/hm~2)could achieve high grain yield,high nitrogen utilization efficiency,and grain quality in this research.Meanwhile,the grain yield and N uptake of silage maize was higher than that in grain maize and fresh maize,which provided an important guidance for maize selection in southwest of China.