Bacillus megaterium strain KGA3 increases saline–alkaline tolerance of maize by recruiting keystone taxa in rhizosphere soil

Background and Aims Available phosphorus (AP) deficiency in severely saline–alkaline soil adversely affects crop growth. To increase soil AP and promote crop growth, a phosphorus-solubilizing bacteria (PSB) named KGA3, which is a strain of Bacillus megaterium, was inoculated on maize. Methods A field experiment was conducted with CK and KGA3 treatment. Co-occurrence network (CoNet) was constructed to identify the keystone taxa, and redundancy analysis (RDA) was carried out to explore the relationships between keystone taxa and soil properties under different treatments to reveal the mechanism by which strain KGA3 promotes crop growth. Results Inoculation with KGA3 significantly increased contents of soil available nitrogen and potassium, activities of dehydrogenase and protease enzymes, and contents of the soil ions water-soluble K+, water-soluble Ca2+, and SO42–. According to co-occurrence networks, PSB community structure was stable with KGA3 treatment. In addition, KGA3 recruited beneficial keystone taxa such as Cyanobacteria to increase soil AP and promote maize growth. Conclusion We demonstrated that Bacillus megaterium KGA3 has potential as a biofertilizer to reduce the application of P fertilizers as well as increase crop productivity under severely saline–alkaline soils in semiarid regions.