Effects Of Biochar Application On Ecological Stoichiometry And Microbial Community Characteristics Of Black Soil

Black soil is one of the most fertile soils in the world with good physicochemical properties and high organic content.However,the quality of black soil in Northeast China deteriorated seriously due to unreasonable cultivation for a long time.Biochar has the properties of high specific surface area,high porosity,high p H value and high C/N,which can restore soil ecology and sequester carbon,and is considered to be an effective conditioner to improve soil quality.To study the effects of biochar on soil physicochemical properties,the activities of C,N and P cycle ecological enzymes and microbial communities,and to understand the effects of biochar on physicochemical properties and various enzyme activities of black soil with the participation of microorganisms,can provide theoretical and practical basis for controlling fertility degradation of black soil.The main results are as follows:1.After 2-5 years of biochar application increased maize yield to varying degrees.In addition,compared with B0 treatment,B10,B30 and B50 treatments significantly increased the average maize yield of 5 years by 15.5%,20.2%and 17.2%,respectively,but from the perspective of economic benefit,B10 treatment had better effect.After 5 years of biochar application,compared with B0 treatment,B50 treatment significantly increased soil saturated water conductivity by 78.6%,and significantly decreased soil bulk density by 9.1%.In addition,the value of soil electrical conductivity first decreased and then increased with the increase of biochar application amount,and reached the lowest value in the B10 treatment.After 5 years of biochar application,compared with B0 treatment,B10 treatment significantly increased soil available potassium（AK）content by 16.5%,while B30 treatment significantly decreased soil AK content by 13.8%.2.After 3-5 years of biochar application,compared with B0 treatment,B30 and B50treatments significantly increased soil organic carbon content.After 3 years of biochar application,compared with B0 treatment,B50 treatment significantly increased soil total nitrogen content by 24.9%.In addition,after 5 years of biochar application,compared with B0treatment,B30 and B50 treatments significantly increased the activities ofβ-1,4-glucosidase（βG）,N-1,4-acetylglucosaminidase（NAG）and alkaline phosphatase（ALP）;After 3 years of biochar application,compared with B0 treatment,B10,B30,and B50 treatments increased leucine aminopeptidase（LAP）activity to varying degrees,while LAP activity was significantly decreased after 5 years of biochar application.In addition,after 5 years of biochar application,compared with B0 treatment,B30 and B50 treatment significantly increasedβG/（NAG+LAP）by 18.1%and 40.8%,respectively;while B10 treatment significantly decreasedβG/（NAG+LAP）by 15.8%and increasedβG/ALP and（NAG+LAP）/ALP by 14.5%and 36.6%,respectively.3.In this study,biochar application significantly increased the relative abundances（RAs）of Bacteroidetes and Proteobacteria and significantly decreased the RAs of Actinobacteria,Chloroflexi,Planctomycetes and Verrucomicrobia.Moreover,the trend of Acidobacteria,Nitrospirae and Planctomycetes among different aggregate fractions was mega-aggregates（>2mm,ME）>macroaggregates（0.25–2 mm,MA）>microaggregates（<0.25 mm,MI）;the RAs of Basidiomycota and Glomeromycota in ME were higher than those in MA and MI.The RA of Ascomycota in MI was the highest among the different aggregate fractions.The co-occurrence networks showed that B10 and B30 treatment enhanced microbial interactions in terms of the number of links and average degree,while the B50 treatment reduced these interactions.Additionally,the microbial interaction in ME was enhanced by biochar application.In conclusion,B10 and B30 treatments can better enhance the microbial interactions,especially in the mega-aggregates.In conclusion,biochar application can significantly improve the maize yield,among which B30 treatment has the highest yield,but considering the economic benefit,B10 treatment is better,and B10 treatment can effectively alleviate soil salt and improve soil AK content.However,after application biochar for 5 years,soil microorganisms treated with B10 were more restricted by N,but less restricted by P,soil microorganisms treated with B30 and B50 were less restricted by N.In addition,B10 and B30 treatments can better enhance soil microbial interactions,especially in the mega-aggregates,while B50 treatment can not only increase soil salinity,but also reduce soil microbial interactions.Therefore,the optimal application amount of biochar to improve soil fertility of black soil in northeast China is 10 t hm^-2.