"Biochar-microbe interaction promotes soybean growth in Saline-alkali land by improving soil nutrients and regulating the rhizosphere microbial Community".

Saline-alkaline land serves as a crucial reserve resource for cultivated land, the improvement and fertility enhancement are essential for mitigating farmland pressure and ensuring food security. This study employed two plant growth-promoting bacteria (PGPB), Sutcliffiella horikoshii and Bacillus subtilis, using individual applications and co-application with biochar in a pot experiment to investigate effects on soybean growth, soil physicochemical properties, and microbial community under saline-alkaline conditions. Five treatments were established, including root irrigation with Bacillus subtilis (Bs), root irrigation with Sutcliffiella horikoshii (Sh), biochar combined with Bacillus subtilis (B-Bs), biochar combined with Sutcliffiella horikoshii (B-Sh), and CK. All treatments significantly improved soybean growth compared to CK, with plant height, fresh weight, and chlorophyll content increasing by 11.00%-57.83%, 10.16%-29.84% and 14.92%-19.81%, respectively. The B-Sh and B-Bs enhanced superoxide dismutase (SOD) and catalase (CAT) activities while reducing Malondialdehyde (MDA) accumulation compared to Sh and Bs, particularly in the B-Bs where MDA content decreased significantly by 57.52%. Furthermore, the B-Sh and B-Bs significantly increased soil nutrient content by 21.77%-199.86% and reduced pH by 0.19 and 0.20 units, salt content decreased by 10.64% -26.24%. High-throughput sequencing revealed that biochar amendment increased the abundance of rhizosphere beneficial genera such as Ensifer, Microvirga, Nonomuraea, and Lysobacter, while maintaining rhizosphere bacterial community stability. In conclusion, PGPB co-application with biochar represents an effective strategy for sustaining soybean production in saline-alkali land.