Bio-fertilizer and rotten straw amendments alter the rhizosphere bacterial community and increase oat productivity in a saline-alkaline environment

Saline-alkaline conditions constrain crop productivity and microbial nutrient cycling in arid and semi-arid regions. This field study in a semi-arid saline-alkaline soil of Northern China evaluated how organic amendments (bio-fertilizer, rotten straw, and their combination) and oat cultivar (tolerant Baiyan2 vs. sensitive Caoyou1) affect oat yield, soil physicochemical properties, and rhizosphere bacterial communities. The combined bio-fertilizer plus rotten straw treatment produced the highest oat yields, reduced soil pH, and increased soil salt content for both cultivars. Baiyan2 exhibited higher bacterial α-diversity, greater relative abundance of Proteobacteria and Acidobacteria, and lower Firmicutes compared to Caoyou1. Rotten straw and the combined treatment decreased bacterial α-diversity and Proteobacteria while increasing Firmicutes; these shifts were positively correlated with soil salt and available N, P, and K. The findings suggest pairing tolerant oat cultivars with combined rotten straw and bio-fertilizer to remediate saline-alkaline soils and improve productivity.