Abstract: 【Objective】To explore the effects of different in-situ returning methods of pepper straw on the structure and diversity of bacterial and fungal communities in soil.【Methods】Taking pepper straw as test materials,a field experiment was performed on the four treatments：non-straw returning（CK）,in-situ straw returning（C1）,in-situ straw returning+straw decomposition agent（C2）,and in-situ straw returning+lime-nitrogen（C3）. The Illumina MiSeq sequencing platform was used to conduct 16S rRNA and ITS high-throughput sequencing of soil bacteria and fungi.【Results】All the three in-situ straw returning methods significantly reduced the soil available phosphorus content（P<0.05） and significantly increased the soil pH value（P<0.05）. C1 and C2 treatments significantly reduced soil total nitrogen,alkaline hydrolysis nitrogen content and electrical conductivity（P<0.05）. C1 treatment significantly increased soil total phosphorus,and available potassium content（P<0.05）. C2 treatment significantly reduced soil available potassium content（P<0.05） and significantly increased soil organic matter content（P<0.05）. C3 treatment significantly increased soil total nitrogen,total phosphorus,available potassium, organic matter content and electrical conductivity（P<0.05）. The dominant bacterial genera（relative abundance≥5%） identified by different treatments were Sphingomonas,S0134_terrestrial_group,Longimicrobiaceae,and C3 treatment significantly increased the relative abundance of Longimicrobiaceae（P<0.05）. The dominant fungal genera（relative abundance≥5%） identified by different treatments were Mortierella,Conocybe,Chaetomium,Myriococcum,Clitopilus,Panaeolus and Humicola. C1 treatment increased the relative abundance of Chaetomium,Myriococcum and Clitopilus,and decreased the relative abundance of Mortierella,Conocybe and Humicola. C2 treatment increased the relative abundance of Mortierella,Chaetomium and Panaeolus,and reduced the relative abundance of Conocybe,Myriococcum and Humicola. C3 treatment increased the relative abundance of Conocybe,Chaetomium and reduced the relative abundance of Mortierella,Myriococcum and Humicola.【Conclusion】Different in-situ returning methods of pepper straw affected soil microbial community structure and physicochemical properties to varying degrees. The effects of in-situ straw returning+straw decomposition agent and in-situ straw returning +lime-nitrogen treatment were better than that of direct in-situ straw returning treatment.

Key words: Pepper straw, In-situ returning, Soil, Bacteria, Fungi, Community structure, Community diversity