Response Of Farmland Soil Microbial Community To Long-term Corn Straw Returning To The Field

Crop straw is rich in elements such as C,N,P and K,as well as organic matter,and it can improve soil particle structure,affect soil permeability,fertility retention and plasticity,improve soil fertility,and play an important role in agricultural resource utilization,soil nutrient cycling and crop growth after being decomposed by microbes.At present,the research on long-term straw-return mainly focuses on its impact on soil physical and chemical properties and enzyme activities,while the research on its impact on soil microbial community is relatively insufficient.In order to explore the effects of long-term maize straw-return on the structure and function of soil microbial communities,the soils of the long-term maize straw-return for 8 years(EY group),14years(FY group)and 16 years(SY group)test field at Liangping Test Base of the Three Gorges Academy of Agricultural Sciences in Chongqing were sampled,and analyzed chemical and chemical properties,enzyme activity and microbial communit y structure for the purpose of exploring the response mechanism of soil microbial community structure and function to long-term maize straw-return.The main conclusions are as follows:(1)Effects of long-term maize straw-return on soil physical and chemical properties and enzyme activitiesWith the increase of the time of maize straw-return,the composition of soil particles did not change significantly;and the content of soil available potassium(AK),microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),organic matter(SOM),total phosphorus(TP)and p H in soils,etc.increased significa ntly(p<0.05),among which AK,MBC and MBN in the SY group increased by 1.19,0.98 and 2.64 times respectively compared with the EY group.The activity of phosphatase(ACP),N-acetylglucosaminidase(NAG),?-glucose Glucosidase(?-GC),cellobiosidase(CBH),leucine aminopeptidase(LAP),?-glucosidase(?-GC)and ?-xylosidase(?-XYS)in soils were significantly up-regulated,and the activity of ACP,CBH and LAP of the SY group increased by 1.19,0.47 and 2.83 times respectively than that of the EY group.Correlation analysis showed that p H,AK,MBC and MBN were the main factors affecting soil enzyme activity.Redundancy analysis showed that AK,MBN and MBC had a great influence on the activity of soil enzymes,of which AK was the main significant influence factor(p<0.05).(2)Effects of long-term maize straw-return on the structure and function of soil bacterial communitiesLong-term maize straw-return increased the richness and diversity of soil bacteria.The dominant phyla of soil bacterial communities were pr oteobacteria,acidobacteria and gemmatimonadetes,etc.,and the results of ?-diversity showed that there were extremely significant differences in the bacterial community structure between different groups(p<0.01).LEf Se analysis revealed that there were 22 species of bacterial populations with significant differences among the three groups.RDA analysis found that TP and AK were the main significant factors affecting the dominant population of bacteria(TOP10).in farmland soil(p<0.05),and their contribut ion rates were 20.8% and 15.2%,respectively.The results of Bug Base analysis showed that long-term maize straw-return increased the relative abundance of Grady's negative bacteria,and the results of KEGG functional analysis showed that long-term maize straw-return had significantly accumulated a number of bacterial populations,whose functions were mainly related to translation,metabolism of terpenoids and polyketides and glycan biosynthesis and metabolism(p<05).The results of FAPROTAX functional prediction showed that the abundance of bacterial population associated with the heterotrophic function of chemical energy were highest in the long-term maize straw-return soil,and the relative abundance of population associated with nitrate breathing and nitrogen respiration increased with the increase of straw-return time.(3)Effects of long-term maize straw-return on the structure and function of soil fungal communitieslong-term maize straw-return also increased the richness and diversity of soil fungal,and the dominant phyla of soil fungi were ascomycota,basidiomycota,mortierellomycota,etc.The results of ?-diversity analysis showed that there were extremely significant differences in fungal communities among the groups(p<0.01).Through LEf Se analysis,it was found that there were 17 species of fungal communities with significant differences among the three groups.RDA analysis found that AP and AN were significant factors(p<0.05)affecting the dominant fungal population(TOP10),and their contribution rates were 15.7% and 13.7 % respectively.The predicted results of fungal nutrition function showed that the fungal communit y composition of the three groups of cropland soils was mostly saprophytic by FUNGuild,and their function were mainly related to the degradation of lignin an d cellulose.In conclusion,long-term maize straw-return had a positive effect on soil chemical nutrients,soil enzyme activities,diversity and function of soil microbial community,with the increase of returning years,soil enzyme activit y,microbial communit y structure and function show a certain saturation effect,which could provide reference for straw-return practice.