Effect Of Plant Density And Nitrogen Application Rate On GHGS Of Maize Field In Northeast China

Rational planting density and appropriate nitrogen application are effective measures to ensure high quality,high yield and high efficiency of crops.At present,the grain system accounts for more than one third of the global greenhouse gas emissions.In order to find out the greenhouse gas emission status and its influencing factors,we monitored the greenhouse gas emission using the static chamber-gas chromatography method to find out effects of density,nitrogen application rate and their interaction on greenhouse gas emissions and the correlation between greenhouse gas emissions and temperature,precipitation and soil properties was analyzed from maize fields in Northeast China.Four kinds of nitrogen application were set up,including m4.5（45000 plants/ha）,M6（60000 plants/ha）,M7.5（75000 plants/ha）and M9（90000 plants/ha）,and three nitrogen application amounts N120（120kg-N/ha）,N180（180kg-N/ha）and N240（240kg-N/ha）.The results are as follows:（1）At different densities,N₂O emission flux is M4.5（453.8μg/m²）<M7.5（528.2μg/m²）<M9（687.5μg/m²）<M6（689.3μg/m²）;CH₄emission flux is M6（9.24μg/m²）<M7.5（11.40μg/m²）<M4.5（14.60μg/m²）<M9（15.35μg/m²）;CO₂ emission flux is M4.5（27.16 mg/m²）<M7.5（35.79 mg/m²）<M6（40.03 mg/m²）<M9（44.44 mg/m²）（2）At different nitrogen application rates,N₂O emission flux is N180（293.7μg/m²）<N120（677.3μg/m²）<N240（929.6μg/m²）;CH₄emission flux is N120（4.09μg/m²）<N240（8.32μg/m²）<N180（13.60μg/m²）;CO₂ emission flux is N120（29.86mg/m²）<N180（32.55 mg/m²）<N240（40.73 mg/m²）（3）The interaction between nitrogen application rate and density significantly affected the greenhouse gas flux and GWP.The GWP is only 415 kg/ha,at the lowest in the treatment of M6+N120,which is about one eighth of the treatment of M9+N240.In the interaction,N₂O,CO₂ and GWP were dominant in density,while CH₄ and GHGI were dominant in nitrogen application.（4）Air temperature,accumulated temperature,atmospheric humidity and precipitation significantly affect the emission of greenhouse gases;soil temperature and humidity significantly affect the emission of greenhouse gases;surface soil microbial biomass nitrogen was significantly correlated with carbon dioxide,and microbial biomass phosphorus was significantly correlated with methane.In this experiment,the diversity and abundance of soil microorganisms（bacteria and fungi）had no correlation with greenhouse gas emissions,while methane had significant correlation with the dominant communities of Acidobacteria in bacteria,Ascomycetes and Mortierellomycota in fungi.