| In order to clarify the suitable nitrogen application rate under the condition of spring maize densification in northern Sichuan irrigation area,the growth and development of spring maize and the greenhouse gas emission in the field under different nitrogen application levels were further revealed,and the best yield and environment win-win for the central and western regions of Inner Mongolia were selected.Nitrogen levels provide a theoretical basis.This study analyzed 6 nitrogen application rates of 0 kg/hm2,120 kg/hm2,180 kg/hm2,240 kg/hm2,300 kg/hm2,360 kg/hm2（N0,N8,N12,N16,N20,N24）.The effect of horizontal on the main agronomic traits,photosynthetic characteristics,yield and greenhouse gas emission of spring maize.The main findings are as follows:（1）The effects of each treatment on plant height,leaf area index and dry matter accumulation of Guangde 5 seedling stage were not significant.Except for the plant height of the big bell stage,the plant height,leaf area and dry matter accumulation of the other growth stages were the highest with N16 treatment,and the nitrogen application was significantly higher than the control.（2）The effects of nitrogen application on photosynthetic characteristics reached a significant level.During N16 nitrogen application,Guangde 5 had a large net photosynthetic rate,stomatal conductance,transpiration rate and smaller grouting during the silking stage.The period of decline,and maintain a large photosynthetic rate during the filling period.（3）The effects of different nitrogen application rates on yield components showed that there was a positive correlation between panicle length,ear diameter,1000-grain weight,grain number per spike and nitrogen application rate（P<0.05）,and they all reached the maximum at N16 treatment;There was a significant negative correlation between the length of the tip and the amount of nitrogen applied（P<0.05）.The yield of Guangde 5 increased first and then decreased with the increase of nitrogen application rate,and the highest yield was 14538.26 kg/hm2when treated with N16.（4）The emission fluxes of CO2 and N2O increase with the increase of nitrogen application rate,and there is no obvious regularity for the emission and absorption of CH4.The total cumulative emissions of CO2 and N2O and the total amount of accumulated and absorbed CH4 increased with the increase of nitrogen application rate.The greenhouse effect increased with the increase of nitrogen application rate;the greenhouse gas emission intensity decreased first and then increased with the increase of nitrogen application rate.Combined with the yield analysis,it was found that the greenhouse gas emission intensity was the lowest and the yield was the highest when N16 was applied.Therefore,the nitrogen application level of N16（240 kg/hm2）is an ideal nitrogen application level in the northern irrigation area of northern China. |
