| Global warming is one of the most serious challenges that human beings have to face in the history.The main cause of global warming is the increase in greenhouse gas emissions.Nitrous oxide(N2O)is an important greenhouse gas in the atmosphere,and the main source of N2O comes from direct and indirect emissions from agricultural soil.Therefore,effective measures for reducing N2O in farmland soil are needed.Biochar is considered as a potential approach,But for paddy soil N2O emission reduction effect exist difference,at the same time,due to the different types and adding amount of biochar on soil N2O emission show different results,it remains to be further research,and the vast number of denitrifying microorganism communities,widely distributed,complex system,need more research to explore the community structure and diversity.In view of this,this study for 2 h under 500?cracking of rice straw biochar(BC-r)and pig manure biochar(BC-s)as the research object,using pot experiment analysis biochar ecological effects on rice soil N2O emission,and through the analysis of paddy soil environmental factors,soil enzyme activity,denitrification function of microorganisms and soil N2O emission production relations,explore the mechanism of denitrifying microorganism paddy soil N2O emission.In order to provide theoretical basis and data support for biochar to alleviate N2O emission from paddy soil.The main conclusions of this paper are as follows:(1)The basic properties of BCr and BCs are different.Both biochar are alkaline and have more functional groups.BCr has more pore structure,larger specific surface area,indicating smoother,less aromatic,and relatively more polar,hydrophilic,showing a large number of Si signals.BCs showed more ash elements(49.93±1.61>47.91±1.52)and higher CEC content.The surface of BCs was obviously rough and showed less pore structure,showing more signals of mineral elements such as P,K,Ca,Mg,Fe,Mn and more C-O-C structures.(2)Two kinds of biochar can be used to reduce the N2O emission of paddy field soil,and the BCs shows a better effect,with 5%additive amount being better than 1%additive amount.During paddy soil culture,N2O emission flux showed a trend of decreasing with the increase of culture time,while the peak N2O emission flux showed irregular changes.The N2O gas emissions of soil added with higher biochar concentration were all at a low level.Biochar input can reduce soil N2O cumulative emissions by 45.14%-73.96%,and 5%biochar added shows lower N2O cumulative emissions.(3)The results of two-factor variance analysis indicated that the type and dose of biochar had certain effects on the concentration of soil environmental factors and the activity of soil enzymes.With the input of biochar,the soil p H value,total N concentration,organic carbon concentration increased by 0.40-1.78 units,7.7%-59.8%,1.04-22.17 mg·g-1,the ammonia nitrogen concentration decreased by 2.5%-36.8%,the nitrate nitrogen(NO3-)concentration,nitrite nitrogen concentration,the microbial nitrogen concentration decreased by 6.27-0.49?g·g-1,13.16-37.72 mg·kg-1,and the soil urease activity increased by 0.01-0.156 mg·NH3-N·g-1·d-1,the activity of nitrate reductase decreased by 1%-80.3%,and the activity of soil protease(PR)changed between 1.41-2.39 mg·glycine g-1·soil·d-1.(4)The effects of biochar on the community structure of two denitrifying microorganisms showed different trends,and the effects of biochar on the relative abundance of different genera were different,The mechanism of denitrification of biochar on N2O emission is closely related to the change of environmental factors and enzyme activity.After biochar input,the relative abundance of Sinorhizobium,Bradyrhizobium,and Rhodoferax had the highest correlation with the N2O cumulative emission flux and reached the significance level(F=0.780,p<0.05),(F=0.517,p<0.05),and(F=0.813,p<0.05).Biochar by influencing the soil NO3-concentration,PR activity makes Sinorhizobium belongs to the relative abundance of change,by influencing the soil TN concentration,NO3-concentration makes Bradyrhizobium belongs to the relative abundance of change,by influencing the p H value,concentration of NO3-,PR activity influence Rhodoferax changes in relative abundance,combined impact paddy soil N2O emissions. |
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