Effect Of Biochar On Soil N₂O Emissions And Nitrification And Denitrification Functional Genes Abundance

In recent years,the global warming caused by greenhouse gas emissions has become more and more serious.Mitigating greenhouse gas emissions has become an urgent problem to be solved.Because of its long residence time in the atmosphere,high temperature increasing potential and its cumulative growth trend,N₂O has become a hot spot of widespread concern,and soil is an important source of N₂O emissions.The research found that the special physical and chemical properties of biochar make it have a non-negligible role in nitrogen fixation and emission reduction.It is of great significance to study the effect of adding biochar on soil properties and the conversion and utilization of soil nitrogen or to promote sustainable agriculture.This paper studies the effects of biochar types,additions,and soil moisture on soil N₂O gas emissions and related microorganisms.By setting different water contents(40%WHC and100%WHC),research the different added species(corn straw biochar,rice husk biochar)and different added levels(0%,1%and 4%w/w)of biochar effects on soil N₂O gas emissions and abundance of microbial functional genes(AOB amo A,AOA amo A,nir S,and nos Z)related to soil nitrogen cycling.The main research conclusions are as follows:(1)When the soil water content is 100%WHC,the addition of 4%rice husk biochar increases the soil nitrification rate,and the addition of 4%corn stover biochar reduces the soil nitrification rate,and as the amount of corn stalk biochar added increased,the soil nitrification rate decreased more,this kind of soil water content is conducive to the progress of denitrification reaction with NO₃^--N as the reaction substrate,resulting in a significant reduction of NO₃^--N content in the soil.Adding 4%corn stover biochar to the soil,the nitrification rate is inversely proportional to the soil water content,NH₄⁺-N concentration is proportional to the water content,40%WHC is more conducive to the nitrification reaction.In this experiment,the water content is 100%WHC treatment is beneficial to soil denitrification.In this experiment,the treatment with water content of 100%WHC is conducive to soil denitrification.(2)When the soil moisture content is 100%WHC,the addition of corn straw biochar promotes the emission of soil N₂O.Among them,the addition of 1%corn straw biochar for the treatment of N₂O emissions is significantly higher than that of the 4%corn straw biochar treatment.4%rice husk biochar inhibits soil N₂O emissions.The effect of biochar on N₂O emissions varies depending on the biochar raw materials.When 4%corn straw biochar was added to the soil,soil N₂O emissions increased with increasing water content.When the water content was 40%WHC,it inhibited soil N₂O emissions,and when the water content was40%WHC,it promoted.(3)When the soil moisture content is 100%WHC,the addition of corn straw biochar will increase the copy number of nir S gene in the soil,and the nos Z gene copy number will decrease.The amount of corn straw biochar added will be the same as the number of AOA amo A and AOB amo A genes in the soil.In any proportion,the addition of 4%rice husk biochar increased the number of AOA amo A,AOB amo A,nir S,and nos Z genes in the soil;with the addition of 4%corn stover biochar,the AOB amo A and nir S gene copy numbers decreased in the soil with 40%WHC soil moisture,the nos Z gene copy number increased,and the AOA amo A gene copy number was greater than 100%WHC soil moisture.When the amount of water is 40%WHC and the addition of 4%corn stover biochar,the soil N₂O emission is the lowest.