Core bacterial communities dominated Purus frumentum biomass under different green manure returning amounts in saline-alkali soil

● P. frumentum biomass could be improved by appropriating returning measures. ● P. frumentum biomass was excellent in 75% alfalfa returning amount. ● Key species of bacteria differed among the alfalfa returning amounts ● The relationship of core bacteria and their potential ecological functions are more close to biomass. The use of green manure returning to field is a common practice in conservation tillage. However, there is limited research on how different amounts of alfalfa can affect saline-alkali soil properties, bacterial community characteristics, and subsequent productivity. In this study, five different amounts of alfalfa return were investigated to understand the biological relationships between rhizospheres soil properties, bacterial communities, potential functions, and the Purus frumentum biomass. The results showed that the biomass was highest when 75% of the alfalfa was returned to the field. This particular amount was associated with relatively low soil pH and electrical conductivity. Additionally, it increased the relative abundance of beneficial bacterial taxa in both core and non-core bacteria. Statistical analysis revealed significant differences in both core (RANOSIM = 0.871, P = 0.001) and non-core (RANOSIM = 0.947, P = 0.001) bacterial communities among the different amounts of alfalfa return based on non-metric multidimensional scaling analysis. Core bacterial taxa and their potential ecological functions were more closely related to plant biomass compared to non-core bacteria based on correlation analysis and multiple regression analysis. Therefore, our results indicate that optimizing the amount of alfalfa return can improve subsequent plant biomass. Regulating soil physicochemical properties and influencing core microbial community structure are of great significance for soil functional stability and crop productivity sustainability.