Abstract: We examined the effects of rotary tillage and straw incorporation approaches on microbial community characteristics of brown soil with a 5-year field experiment in Tieling, Liaoning Province. There were four treatments: (1) whole soil layer rotary tillage without straw incorporation (RT); (2) ridges of rotary tillage without straw incorporation (RR); (3) whole soil layer rotary tillage with straw incorporation (RTS); and (4) ridges of rotary tillage with straw incorporation (RRS). The results showed that compared with no straw incorporation (RT and RR treatments), RTS and RRS treatments significantly increased the relative abundance of Proteobacteria,  Acidobacteria, Chloroflexi, and Ascomycota, and decreased the relative abundance of Actinobacteria, Patescibacteria, Firmicutes, WPS-2, and Basidiomycota. Bacterial and fungal gene copy numbers, Chao1 index and Shannon index under straw incorporation treatments were 130.0%, 15.9%, 14.9% and 185.1%, 31.9%, 28.4% higher than those under no straw incorporation treatments, respectively. Compared with RRS, RTS increased the bacterial and fungal gene copy numbers by 40.9% and 50.1%. Results of the bacterial-fungal co-occurrence network analysis showed that RTS and RRS treatments significantly increased the nodes, links, and average connectivity degree. Moreover, RRS had the highest positive link percentage. Bacterium Ellin 6519 and Knufia were key microorganisms under straw incorporation treatments. There was a significant positive correlation between soil bacterial and fungal gene copy number and community diversity. The structural equation modeling showed that soil organic carbon content and bulk density directly affected bacterial community characteristics, while soil organic carbon content and leucine aminopeptidase activity directly affected fungal community characteristics. The results provide a theoretical basis for analyzing the effects of straw strip incorporation with rotary tillage on microbial community in brown soil.

Key words: strip rotary tillage, straw incorporation, soil bacteria, soil fungi, community structure, community diversity.