Effects Of The Interaction Of Planting Density And Nitrogen Application Rate On Nitrogen Utilization Efficiency And Yield Of Spring Maize

At present,maize plays an important role in national food production.Reasonable close planting and scientific fertilization are important measures for high yield and high efficiency of maize.In this study,the interaction of planting density and nitrogen application rate on yield and nitrogen utilization efficiency(NUE)was determined in the field trial in the Northeast China.Two maize varieties(Zhengdan958(ZD958)and Jidan66(JD66)),four planting densities including 45,000(M4.5),60,000(M6.0),and 75,000(M7.5),and 90,000plants/hm~2(M9.0),and three nitrogen application rates such as 120(N120),180(N180),and 240 kg-N/hm~2(N240)were carried out.Meanwhile,a treatment without nitrogen applied(N0)was set at the density of 75000 plants/hm~2.The results showed that:(1)Under the experimental conditions,the accumulation and distribution of dry matter was significantly affected by the density and nitrogen application rate.The accumulation dry matter under different treatments gradually increased after the silking stage,and which was positive correlated with plant density.Meanwhile,the accumulative dry matter increased first and then decreased with the increasing of nitrogen application rate,and which was the highest at N180.Before the physiological maturity(R6),the effects of density,nitrogen application rate and their interaction on the dry matter distribution ratio were not significant,while which was opposite on ZD958 at physiological maturity;meanwhile,JD66 was affected by nitrogen application and nitrogen-density interaction.The contribution rate of dry matter transport in vegetative organs of ZD958 to grain yield was lower than that ofJD66.The contribution rate of ZD958 under M9.0 and N240 treatments exceeded20%,and which of JD66 at N0,N240 and N120 exceeded 20%.(2)Density and nitrogen application rate significantly affected the accumulation of nitrogen content per plant and the accumulation population nitrogen.The nitrogen content per plant decreased with the increasing of density,while the nitrogen content of the population was opposite.Density,nitrogen application rate and their interaction significantly affected the agronomic efficiency of applied N(AEN).Density and nitrogen application significantly affected partial factor productivity from applied N(PFPN);density,nitrogen application and their interaction significantly affected PFPN of JD66.At the same density,the PFPN gradually decreased with the increasing of nitrogen concentration.The effects of density,nitrogen application rate and their interaction on nitrogen harvest index(NHI)were not significant.Density and nitrogen-density interaction have significant effects on nitrogen translocation efficiency(NTE).Meanwhile,the nitrogen contribution proportion(NCP)was significantly affected by density while which was not by nitrogen application rate.(3)The yield was affected by the density,fertilization amount and nitrogen-density interaction.The yields of the two varieties(ZD958 and JD66)increased firstly and then decreased with the increasing of density and nitrogen application rate.Under the same nitrogen level,the yield at M9.0 treatment was lower than that of other densities.Under the same density treatment,the yield at N0 were lower more than 20% than that of other treatments.The yield of ZD958 reached the maximum at M6.0 and N180 treatment,and the yield of JD66 reached the maximum at M7.5 and N240 treatment.Under the same nitrogen application rate,the yield at M9.0 treatment was lower than that under of other densities treatments,the yield at N120 and N180 of M9.0 were lower more than 10% than that of other treatments.Under the same density treatment,the yield at N0 treatment were lower more than 20% than that of other treatments.Meanwhile,the maize ears were not growing well at M9.0 and N0 treatments,the length and thickness of the ear were smaller,while the bald length was longer than that of other treatments.The yield washigher and the yield components were good at the density of 60,000 and 75,000plants/hm~2,and at 120-180 kg/hm~2 of N.The results indicated that the yield and the ear growth would be enhanced through the increasing of planting density and the reduction of nitrogen input appropriately.(4)Density and nitrogen application rate significantly affected stem diameter,ear height coefficient(EHE),leaf area index(LAI),and light use efficiency of spring maize.Plant height was significantly affected by nitrogen application rate.At the same density,the plant height at N180 treatment was the highest,which at N0 treatment was lowest;at the same nitrogen application rate,the trend of different densities was not obvious.The stem diameter at M9.0 was significantly lower than that at M4.5 treatment,and which was slimmer at M9.0,N0 or N240.The EHE was positively correlated with the density;with the increase of nitrogen application rate,the EHE showed an increasing-lowering-increasing trend.LAI was positively correlated with density.At the same density,the trend of different nitrogen application rates was not obvious;which decreased faster while the leaf senescence speed increased after the silking stage at M9.0 and N0.(5)There was a difference in net photosynthetic rate(Pn)between different varieties.Pn of ZD958 was significantly higher than that of JD66.There was no significant difference on Pn under different densities and nitrogen application rates.Density and nitrogen application significantly affected the light use efficiency of spring maize.The light use efficiency increased first and then decreased with the increasing of density at the same N level.The light use efficiency of ZD958 and JD66 reached the maximum at M7.5 treatment.The light use efficiency increased first and then decreased with the increasing of nitrogen concentration at the same density.The light use efficiency of both varieties was the lowest at N0,and the application of nitrogen fertilizer could significantly improve the light use efficiency of spring maize.