Effect Of Biogas Residues On Microbial Community Structure And Function In Saline Soil

Soil microbes are sensitive to environmental changes.The application of foreign substances not only affects the physicochemical properties of salinized soil,but also profoundly changes the microbial community structure and function of salinized soil,thereby improving soil quality.In this paper,the secondary saline field in Tuoketuo County,Inner Mongolia,was used as a field test for the biogas residue improvement experiment.The microbial bacteria and fungal community structure of salinized soil were studied by using Illumina Miseq high-throughput sequencing technology and Biolog-ECO microplate technology.The effects of the biogas residue on the enzymatic activity,microbial biomass and culturable microbial population of saline-alkali soil were investigated,and the effects of biogas residue on the microbial community of saline-alkali soil were analyzed.The main findings and conclusions are as follow:1.Illumina Miseq high-throughput sequencing technology compares unmodified saline-alkali soil,farmland soil,first-year modified plot soil with 4 kg/m~2 of biogas residue application,and improved second-year plot soil bacterial community structure and fungal community structure.The results of bacterial community structure analysis showed that:1)The composition of bacterial community structure in saline-alkaline soil was adjusted with the application of biogas residue.The heat map and principal component analysis showed that the bacterial microbial community structure of the first-year modified plot soil and farmland soil was similar.The bacterial microbial community structure of the second-year improved plot soil and saline-alkali soil was smilar.The composition of the dominant bacterial flora of saline-alkaline soil was changed.The dominant phylm was changed from Proteobacteria and Actinobacteria to Proteobacteria and Acidobacteria;The dominant order was transformed from Acidimicrobiales,Subgroup-6,Sphingomonadales,Rhizobiales,and Gemmatimonadales to Subgroup-6,Sphingomonadales,Subgroup-4 and Acidimicrobiales;The relative abundance of beneficial bacterial microbial populations in the saline-alkaline soil was significantly increased.Such as the abundance of subgroup-4 belonging to Acidobacteria was significantly improved.The abundance of Bradyrhizobium?Rhizobium?Arthrobacter?Sphingomonas and Nitrosomonadales which were functional bacteria associated with elemental circulation were significantly improved;The relative abundance of salt-tolerant bacteria such as Actinomadura,Paenisporosarcina and Methylohalomonas was significantly reduced with the application of biogas residue.2)The dominant phlym of soil fungal community in four-sample were Ascomycota,Zygomycota and Basidiomycota.The relative abundance of Ascomycete and Basidiomycetes wasincreased with the application of biogas residue.The relative abundance of the zygomycetes was reduceed with the application of biogas residue;The structural composition of the dominant genus of the saline-alkaline soil fungi was changed from Mortierella and Chaetomium to Mortierella and Gibberella,which is consistent with the dominant species of farmland;The relative abundance of phosphate-dissolving microorganisms such as Penicillium was increased with the application of biogas residue;The richness index of fungal communities was increased,the diversity index of fungal communities was reduced with the application of biogas residue on the saline-alkaline soil.2.The Biolog-ECO microplate technique was used to compare and analyze the soil microbial functional diversity of the unmodified saline-alkali land and the improved plot which the applied amount of biogas residue was 2,4,8,and 12 kg/m~2.The results showed that the type of carbon source which was used by salinized soil microorganisms was changed.The utilization of carbohydrates and amine carbon sources by soil microorganisms were increased,the utilization of phenolic carbon sources was reduced;The structural composition of carbon metabolic function was changed.The carbohydrate,amino acid and phenolic carbon source were the main factors;The soil microbial functional diversity index indicates that the Shannon index and the Simpson index of the microbial functional diversity of the saline-alkaline soil were significantly increased when the amount of the biogas residue was more than2kg/m~2.3.Comparative analysis of soil enzyme activity,microbial biomass and culturable microbial population of farmland,saline-alkali land,first-year improved plots with 2,4,8,and 12 kg/m~2 of biogas residue applied and the second year improved plots.The results showed that:1)The application of biogas residue has significant effects on salinized soil enzymes.The effects of biogas residue on soil invertase?urease?peroxidation of hydrogenase and alkaline phosphatase activity was different.The activity of invertase,urease and alkaline phosphatase were significantly increased,the activity of catalase was reduced in the first year.The activity of sucrase,urease and alkaline phosphatase were increased in the second year,the activity of hydrogen peroxide Enzyme activity was reduced.2)The effect of different amount of biogas residue on soil enzyme activity was different.The activity of invertase,urease and alkaline phosphatase were significantly increased in the second year when the application amount of biogas residue was12kg/m~2.3)The application of biogas residue has a significant effect on the microbial biomass of saline-alkaline soil.The effect of the first year of biogas residue on the microbial biomass carbon and nitrogen in saline-alkaline soil was not significant.The microbial biomass carbon was increased in the second year when the amount of biogas residue applied was 8kg/m~2,The soil microbial biomass nitrogen was significantly increased when the application of the biogas residue was 12 kg/m~2.4)The number of culturable bacteria was reduced and the number of culturable fungi was increased with the application of biogas residue.Especially in the second year,the ratio of culturable fungi/bacteria was significantly increased when the application amount of biogas residue was 4kg/m~2.The above results indicate that the biogas residue has an effect on the soil bacterial and fungal community structure,soil enzyme activity,microbial biomass,and culturable microbial population.The changes in soil enzyme activity and soil microbial biomass indicated that the high applied amount of biogas residue showed positive effects on saline-alkali soil microbes as the application time prolonged;high-throughput sequencing showed that when the applied amount was 4 kg/m~2,the biogas residue had a positive impact on the composition of bacteria and fungal communities in saline-alkaline soils,but this effect could not be extended to the second year.In general,the addition of biogas residue has a positive effect on the improvement of salinized soil quality.This study can provide basic data for the improvement of saline-alkali soil,and also has a certain significance for the theoretical study of soil microbial community structure and dynamics in saline-alkali soil.