| Global warming has become one of the major environmental problems,and greenhouse gas emission is the main cause of global warming.As one of the important greenhouse gases,The global warming potential of nitrous oxide（N2O）is 298 times of carbon dioxide（CO2）.Agricultural soil has been confirmed to be the largest anthropogenic source of atmospheric N2O emissions in the world.At present,a number of mitigation measures have been proposed for N2O.Biochar and chemical nitrification inhibitors have also been widely recognized for reducing N2O emissions.In this paper,we collected soil samples from vegetable field,tea plantation,peach orchard（one year）,peach orchard（seven years）to explore the effect of biochar and chemical nitrification inhibitor and their combined application on N2O emission a incubation experiment.In this study,five treatments including control（CK）,urea application alone（U）,combined application of biochar and urea（U+BC）,combined application of chemical nitrification inhibitor DMPP and urea（U+DMPP）,combined application of biochar and chemical nitrification inhibitor DMPP and urea（U+BC+DMPP）were established for four agricultural soils.After 40 days of incubation,The N2O emission flux was measured during the incubation period,the physicochemical properties and the abundance of nitrifying/denitrifying microbial functional genes of soil samples were analyzed.The effects of biochar and chemical nitrification inhibitor DMPP on N2O emission and the underlying microbial mechanism were investigated by repeated measurement analysis of variance,correlation analysis and stepwise regression analysis.The results of this study are presented as follows:1.The addition of DMPP significantly reduced the N2O emissions of the four agricultural soils（57%-74%）.However,biochar had different effects on N2O emission from different soils.It reduced N2O emission from vegetable soil and tea plantation soil（56%,13%）,but increased N2O emission from peach orchard soil.The combined use of biochar and biochar had a further reduction effect（80%）on N2O emission in vegetable soil,but reduced the effect of DMPP in other soils.2.There was a significant positive correlation between N2O flux and NH4+-N content in vegetable soil（P<0.001）.The N2O emission flux of tea plantation soil was positively correlated with the contents of NH4+-N and DOC in the soil and soil p H value（P<0.05）.The N2O emission flux of peach orchard soil was positively correlated with the content of NH4+-N and soil p H value,and negatively correlated with the content of NO3--N in soil（P<0.05）.There was a significant positive correlation between the N2O flux and the content of NH4+-N in the soil and the p H value of the soil（P<0.05）.By quantitative analysis of functional genes related to nitrogen cycle,it was found that N2O flux of vegetable soil was negatively correlated with nir S and nir K（P<0.01）,and N2O emission of tea plantation soil and peach orchard soil was positively correlated with AOB（P<0.05）.3.According to the stepwise regression model,when physicochemical factors were considered separately,the explanatory degrees of physicochemical factors on N2O emission in agricultural soils were 36%,22%,32%and 17%respectively（vegetable field,tea plantation,one-year peach orchard and seven-years peach orchard）,the physicochemical factor with the highest explanatory degree was NH4+-N.After further consideration of microbial factors,the interpretation degree of the model is improved.NH4+-N was the highest physicochemical explanatory factor,AOB（15%）and nir K（15%）were the highest explanatory microbial factors in vegetable soil,and AOB（16%,17%,39%）were the highest explanatory microbial factors in tea plantation soil and peach orchard soil（one-year,seven-year）.The explanation degree of physicochemical factors for N2O emission in vegetable soil,tea plantation soil and one-year peach garden soil were 45%,48%and 49%,respectively,which were higher than that of microbial factors（33%,23%and 21%）.Microbial factors（53%）explained more N2O emission than physicochemical factors（23%）.Firstly,in conclusion,the response of N2O emission of agricultural soil to the addition of biochar and chemical nitrification inhibitor DMPP and its underlying mechanism were affected by different agricultural soil types.Secondly,when biochar and DMPP are applied together,biochar not only antagonizes DMPP,reduces the effect of DMPP on N2O emission.It is also possible to synergise with DMPP to achieve further N2O reduction.This is mainly affected by the adsorption of biochar on DMPP and the main pathway of N2O emission from soil.Thirdly,soil physicochemical factors are the dominant factors driving N2O emissions,but with years of crop cultivation increasing,the contribution of microbial factors to soil N2O emissions will increase. |
