Study On The Effect Of Straw Addition On The Physical And Chemical Properties And Microbial Diversity Of High Organic Matter Acid Soil

In some parts of southern my country,such as Tengchong,Yunnan,due to the high rainfall,relatively low temperature,and large amounts of chemical fertilizers,the current situation of the local soil environment is high organic matter content,serious acidification,unreasonable humus composition,and the microenvironment suffers damage.There is a close relationship between the addition of organic materials,the content of humus components,soil pH and soil microorganisms,and they affect each other.In view of the current ecological environment of high-organic acid soils,it is necessary to optimize the extraction method of humic acid,and to study the effects of adding different types of straw(fresh,decomposed)on soil pH,organic carbon components,and microbial communities.To this end,this study took the high-organic acid soil in Tengchong,Yunnan as the research object,and optimized the extraction method of humic acid based on response surface methodology.Using indoor cultivation experiments,it analyzed the effects of different types of straw on the pH and organic carbon components of the high-organic acid soil.The impact of microbial structure and composition changes based on high-throughput sequencing analysis.Through the test,the results show that:(1)Humic acid is an active substance in soil humus,and its change is closely related to soil microorganisms and pH.Extracting humic acid from the soil as much as possible is the basis for correct evaluation of the environmental quality of high organic matter acid soil.In response to this situation,this paper carried out an optimized extraction experiment of humic acid,using Box-Behnken response surface method to obtain the optimal extraction plan for humic acid in acid soil with high organic matter: Na OH concentration 0.16mol/L,alkaline extraction time 15.00 h,The solid-liquid ratio is 0.08,and the alkali extraction temperature is40°C.The regression model equation has a determination coefficient of R2 = 0.9911 and a coefficient of variation of 2.05.The test is reliable and can be used for the optimization analysis of the humic acid extraction scheme.The optimized method has complete extraction and good stability,and has little effect on the properties of humic acid.(2)The effect of straw addition on the pH and organic carbon components of high organic matter acidic soils showed that compared with CK treatment,the addition of decomposed rape straw treatment had the best effect on increasing the soil organic matter content,increasing by 52.52%～101.23%;adding decomposed rice Straw treatment has the best effect on increasing soil pH and extractable humus.pH increased by 24.23%～30.96%,humic acid increased by 44.30%～189.34%,and fulvic acid increased by 0.24%～127.22%;at the end of the cultivation,the pH increased by 24.23%～30.96%,humic acid(HA)increased by 44.30%～189.34%,and fulvic acid(FA)increased by 0.24%～127.22%.After adding straw,the molecular complexity is lower,the aromatic nucleus group is less,and the degree of condensation is lower.(3)By studying the effect of adding straw on the diversity of soil bacteria and fungi,the results show that the dominant bacteria phyla are Proteobacteria,Actinobacteria,Bacteroidetes,and their relative abundance.The ranges were 28.89%-69.95%,5.81%-54.07%,4.91%-26.59%.The dominant phyla of fungal communities are Ascomycota,Basidiomycota,and Zygomycota.Their relative abundance ranges from 21.76%-86.56%,5.20%-48.88%,0.48%,respectively.-43.29%.Based on the OTU dilution curve,it was shown that compared with the CK treatment,the bacterial species richness of the treatment with decomposed straws reached the highest at 30 days of culture,while the treatment with straws reduced the fungal richness.At the end of 90 days of culture,the Chao1 index and Shannon index of the bacteria and fungi in the samples showed no significant difference between the treatment groups.Principal component and cluster analysis showed that the bacterial community structure of adding fresh straw or decomposed straw was similar at 0-7days.At 30-90 days,the same treatment group gathered together or on a branch over time.The community composition is similar and gradually reaches a stable state.The treatment of adding decomposed rape straw has been far away from other samples,indicating that the fungal community structure is obviously different from other straw treatments.Redundancy analysis(RDA)results show that pH and organic carbon components(without HA)are negatively correlated with the bacteria in most treatment groups,which are related to Enterobacter and Pseudarthrobacter.)The degree of correlation is relatively high,and there is no significant correlation with other bacterial genera.The pH and organic carbon components are highly correlated with fungal community composition,and highly correlated with the addition of decomposed rape straw.From the results of this study,the return of decomposed rice straw to the field has a better effect on increasing bacterial diversity,and the return of decomposed rape straw to the field has a certain effect on the fungal community structure.In summary,the optimized extraction method of humic acid in this article is completely and stable,and can replace the traditional IHSS method for extracting humic acid from acid soils with high organic matter.Adding decomposed rice and rape stalks can improve the composition and ratio of humus,increase the diversity of bacteria and microorganisms in a short period of time,without destroying the original micro-ecological environment,and increase the pH value of acidic soils with high organic matter.Therefore,the return of 4%decomposed rice and rape straw to the field can replace the direct return to the field for the improvement of high organic matter acidic soil,which has the value of promotion and application.