This study investigates the dual impacts of biochar amendment on the physicochemical properties and microbial community of saline-alkali soils, and delves into the underlying mechanisms. Field plots were established in a representative saline-alkali region, with treatments varying in biochar feedstock and application rate. Soil pH, organic matter content, electrical conductivity, and soluble salt concentration were monitored, while high-throughput sequencing was used to assess shifts in microbial community structure and functional gene abundance. Results showed that biochar significantly reduced soil pH, increased organic matter, improved aggregate stability, and curtailed soluble salt migration. On the microbial level, biochar enhanced bacterial diversity and the abundance of key functional taxa, enriching genes related to nitrogen and phosphorus cycling. Mechanistic analysis indicates that biochar’s porous structure and surface functional groups regulate soil moisture retention and nutrient adsorption, while providing a stable habitat for microbes. These synergistic effects collectively elevate saline-alkali soil quality. The findings enrich the theoretical framework for biochar-based soil remediation and offer scientific guidance for the efficient utilization and sustainable management of saline-alkali lands
