Response Analysis Of Yield And Nitrogen Efficiency Of Spring Maize Varieties With Different Nitrogen Efficiency To Nitrogen Density Interaction Under The Condition Of Soil Fertility Improvement

In order to clarify the optimal nitrogen application rate and suitable planting density of maize varieties after the improvement of soil basic fertility,the nitrogen-efficient variety Xianyu 335 and the nitrogen-inefficient variety Nonghua 101 were selected as experimental materials under the condition of deep straw returning to improve soil fertility.Three densities D1(6.75×10⁴ plants·hm^-2),D2(8.25×10⁴plants·hm^-2)and D3(9.75×10⁴ plants·hm^-2)were designed.The four nitrogen application levels N0,N1,N2 and N3 were(0,210,255,300kg·hm^-2).The response of agronomic traits,photosynthetic characteristics,nitrogen use efficiency and yield of spring maize with different nitrogen efficiency to different densities and nitrogen application rates under the condition of straw returning to improve soil fertility was studied.By appropriately reducing nitrogen fertilizer on the basis of increasing density to obtain higher maize yield and improve the utilization efficiency of nitrogen fertilizer,the combination of density and nitrogen application rate suitable for local production was found,which provided a theoretical basis for further realizing high yield and high efficiency of maize in Inner Mongolia.The main results are as follows:（1）Under the condition of straw returning to improve soil fertility,the yield and nitrogen efficiency of N-efficient maize variety XY335 were significantly higher than that of N-inefficient maize variety NH101.There was no significant difference between yield of15%nitrogen reduction（255 kg/hm²）and that of normal nitrogen application（300kg/hm²）,but nitrogen partial productivity was significantly increased by 15.19%compared with normal nitrogen application.The planting density had a greater effect on maize.When the planting density increased by 10000 plants/hm²,the yield increased by 78.877 kg/hm²,the number of grains per ear decreased by 38.304 grains and the weight of 100 grains decreased by 12.692 g.（2）Under the condition of straw returning and soil fertility improvement,the plant height,ear height and stem diameter of XY335 were significantly higher than those of NH101,and the leaf inclination angle was significantly lower than that of Nonghua101.There were significant or extremely significant differences in the interaction between nitrogen application rate×variety and nitrogen application rate×planting density.There were significant or extremely significant differences in plant height,stem diameter and leaf inclination angle between nitrogen application rate×variety×planting density.With the increase of planting density,plant height and ear height increased significantly,stem diameter and leaf angle decreased significantly.With the decrease of nitrogen application rate,plant height,ear height and stem diameter decreased,and leaf angle increased,but there was no significant difference between 15%nitrogen reduction（255 kg/hm²）and normal nitrogen application（300 kg/hm²）.（3）Under the condition of straw returning and soil fertility improvement,the SPAD value,net photosynthetic rate,canopy transmittance and leaf area index of XY335 were significantly higher than those of NH101.With the increase of planting density,SPAD value,net photosynthetic rate and canopy transmittance decreased significantly,and leaf area index increased significantly.With the decrease of nitrogen application rate,all photosynthetic indexes decreased.There was no significant difference between 15%nitrogen reduction（255 kg/hm²）and normal nitrogen application（300 kg/hm²）under the same planting density.（4）Under the condition of straw returning and soil fertility improvement,the dry matter accumulation per plant and population,the dry matter accumulation rate before and after anthesis,and the nitrogen accumulation per plant and population of XY335 were significantly higher than those of NH101.Under the same planting density,there was no significant difference in dry matter accumulation of single plant and population and nitrogen accumulation of single plant and population between 15%nitrogen reduction（255 kg/hm²）and normal nitrogen application（300 kg/hm²）,but the dry matter accumulation rate before flowering increased significantly and the dry matter accumulation rate after flowering decreased significantly.（5）Comprehensive analysis of agronomic traits,photosynthesis,nitrogen accumulation,dry matter accumulation,yield and nitrogen efficiency of nitrogen efficient and inefficient varieties,it is suggested that after straw returning to improve soil fertility in production,the planting density increased to 9.75×10⁴ plants·hm^-2,and the nitrogen application rate decreased to 255 kg/hm²,which can achieve the purpose of improving maize yield and nitrogen efficiency.