Effects Of Interspecific Interactions Between Potato ? Maize Intercropping On Soil Microbial Community

In order to reveal the effect of intercropping interspecific interaction on soil microorganisms,this paper takes the farmland of potato intercropped with maize consecutive intercropping for six years as the research object,and sets up three treatments:monoculture maize(M),monoculture potato(P)and potato intercropped with maize(PM),and evaluates whether the intercropping has yield advantage by land equivalence ratio(LER)and interspecific competitiveness.The microbial biomass in bulk soil and rhizosphere soil was determined by the method of phospholipid fatty acid.The diversity and community composition of functional microorganisms(AM fungi)in rhizosphere of potato intercropped with maize were studied by high-throughput sequencing.Finally,the species classification and metabolic pathway of all microorganisms in rhizosphere soil of potato intercropped with maize were studied by Metagenomic sequencing,so as to reveal the response mechanism of soil microorganisms to intercropping comprehensively.The main conclusions are as follows:(1)After continuous potato intercropped with maize had caused continuous soil nutrients depletion after six years,but compared with monoculture,intercropping significantly increased soil total phosphorus content;The intercropping of potato and maize had yield advantages,and the land equivalent ratio LER ranges from 1.00 to 1.22.The interspecific competitiveness of maize relative to potato changes with planting period,and the competitiveness of maize to resources was stronger than that of potato before two years,and the interspecific competition was greater than mutual benefit;The middle two years,potato was more competitive than maize,but its competitive advantage was weaker.In the last year,the intensity of competition between them gradually decreased with the years of planting,which was close to 0,indicating that the promotion of interspecific mutualism was gradually dominated.(2)The microbial biomass of rhizosphere soil marked by phospholipid fatty acid was higher than the bulk soil.Continuous intercropping of potato and maize significantly increased the biomass of total Arbuscular Mycorrhizal fungi in soil.Compared with monoculture maize rhizosphere,the biomass of bacteria,G+and G-in rhizosphere soil of intercropping maize was significantly higher than that of monoculture by 33.33%,38.14%and 31.13%respectively,the neutral fatty acids,total biomass,neutral lipid/phospholipid of AM fungi and total microbial biomass of intercropping maize rhizosphere soil increased significantly by 2.87%,2.47%,3.29%and 0.94%.(3)Potato intercropped with maize significantly decreased Chaol index of AM fungi in rhizosphere soil,and significantly affected the community structure of AM fungi in rhizosphere soil,however,Glomus,Paraglomus and Claroideoglomus were the dominant AM fungi in each treatment,and the relative abundance of Glomus was significantly higher in maize rhizosphere than in potato rhizosphere.Available phosphorus,water content,pH,microbial biomass carbon,total phosphorus and available nitrogen contents in rhizosphere soil were the main factors affecting AM fungi Chao1 index and community relative abundance.(4)The results of metagenomic sequencing showed that the species of soil microorganisms were bacteria,eukaryotes,archaea and viruses in descending order.Intercropping and crop types cause changes in the composition of rhizosphere soil microbial community,and Proteobacteria and Actinobacteria were the dominant bacteria,accounting for 71.85%-79.28%.At the genus level,the relative abundance from high to low was uc_Proteobacteria,uc_Actinobacteria,Streptomyces,Bradyrhizobium,Sphingomonas,Conexibacter,Burkholderia,and so on.Intercropping had no significant effect on rhizosphere soil microbial alpha diversity.(5)The prediction results of KEGG metabolic pathway showed that,the relative abundance of primary biological metabolic function pathway analysis from high to low was metabolism,genetic information processing,environmental information processing,cellular processes,human diseases and organismal systems.There were 23 secondary functional layers with relative abundance above 1.0%.Among all microorganisms involved in metabolism,the relative abundance of carbohydrate metabolism is the highest,followed by amino acid metabolism and energy metabolism.There were significant differences in the relative abundance of genes in the secondary functional layers.There were significant differences in microbial communities(P=0.022)and functional metabolic pathways(P=0.029)among the four treatments.Microbial communities and metabolic pathways were influenced by soil physical and chemical properties.