Effects Of Abiotic And Biological Factors On The Formation Of Soil Aggregates And Soil Enzyme Activities

Soil aggregates are an important part of the soil and play an important role in the soil.In this paper,different soils were collected from three areas,Hainan banana garden soil,Nanjing yellow brown soil and Qinghai saline soil.The effects of different factors on the formation of soil aggregates were investigated by design of soil culture experiment to control abiotic factors and biological factors.The results are as follows:1.Effects of indoor stress cultivation on soil physical and chemical properties and microbial community structure.(1)The results showed that there were significant differences in the physical and chemical properties of soil samples after treatments,compared with control.Mean values of total carbon and total nitrogen significantly were reduced after treatments,and lower 5.96%-51.33%than the control(except for the brick red soils with wet treatment).The proportion of the macro-aggregates were significantly increased with acidification treatment,in the>2 mm aggregates,the percentage of silt loam(ST)and sandy loam(SD)was 1.42 times,3.15 times that of control,but that was significantly decreased with wet treatment,in the>2 mm aggregates,the percentage of ST and SD were 0.38 times that of control.The activitives of soil invertase,urease,neutral phosphatase and catalase were reduced about19.28%-89.29%after different treatments.the numbers of soil bacteria and fungi population significantly were reduced after different treatments,while the number of Fusarium population significantly was increased with acidification and pathogen invasion treatments.(2)By extracting soil DNA and Miseq sequencing,it was found that the soil microbial community structures changed significantly with dry,wet,acidification and pathogen invasion treatments.In the bacterial community structures,the relative abundance of Acidobacteria,Bacteroidetes and Gemmatimonadetes were significantly reduced,the relative abundance of Firmicutes and Proteobacteria were significantly increased.In the fungal community structures,the relative abundance of Ascomycota(Fusarium with sexual reproduction is the phylum)was significantly increased with dry,wet,acidification and pathogen invasion treatments.By extracting soil DNA and Miseq sequencing of 0.25-2 mm aggregates,it was found that the community structures of bacteria and fungi in soils with 0.25-2 mm soil aggregates changed significantly after different treatments.In the bacterial community structures,the relative abundance of Acidobacteria and Proteobacteria were significantly reduced,the relative abundance of Firmicutes was significantly increased.In the fungal community structure,the relative abundance of Ascomycota was significantly increased with dry and pathogen invasion treatments.There was also a significantly change in the level of the genus.The results showed that Soil aggregates can not stabilize soil microbial community structures.2.Three strains of microbes secreted extracellular polymers were screened,strain R1,G-C and P-C3 were identified as Rhodotorula mucilaginosa,Rhizobium lusitanum and Enterobacteriaceae sp.respectively.The extracellular polymers content of strain R1 and G-C was the highest at 2485 mg/L and 276 mg/L,respectively.P-C3 was cultured after 2 days,the pH value decreased to 3.6,the effective phosphorus concentration was 500 mg/L.The functional microbes were used in culture experiment and cucumber pot experiment.(1)The results showed that inoculation of capsular functional microbiological treatment,inoculation of.antagonistic microbiological treatment and inoculation function of microbial compound treatment in the>2mm particle size aggregates ratio were the control treatment 7,3,7.5 times,which the effect of inoculated with capsule functional microbial treatment to form macro-aggregates(>0.25 mm)was best,the proportion of macro-aggregates up to 22%.The enzyme activity of the mixed microbial treatment was the highest,the invertase,urease and neutral phosphatase were significantly increased,compared with the control.(2)The results of pot experiment showed that the plant height of cucumber plants treatments with inoculated capsular· functional microbes,inoculated antagonisticmicrobiological treatment and inoculated mixed microbes was increased by 20%,15%and 50%,respectively.The treatments of inoculating antagonistic microorganisms had the highest biomass,28.25 g/pot.Compared with the soil culture experiment,the ratio of each treatment macro-aggregates(>0.25 mm)was significantly increased.After the potting,the the>0.053mm aggregates of other treatments was significantly increased.3.The results of saline soil culture experiment showed that the effect of treatment of inoculating indigenous microorganisms and organic fertilizers was better than that treatments of inoculating exogenous microorganisms and organic fertilizers in soil pH,EC value,aggregates formation and microbial quantity.The treatment of inoculation of indigenous microorganisms and the addition of semi-decomposed organic materials were the best.The soil pH was the most obvious,which was 0.6 units lower than that of the control treatment;and the value of EC was 0.4 units lower than that of the control treatment.The formation of soil aggregates(>2 mm)was better than other treatments,while the other treatments have no aggregates in>2 mm,and increased the proportion of 2-0.25 mm aggregates;the treatment also significantly improved soil enzyme activity and soil respiration strength.The experimental results provide a theoretical reference for the improvement of saline soil.