Bacillus subtilis-Amended Bio-Organic Fertilizer Promotes Peanut Growth by Reshaping Soil Microbiome

Understanding how functional microorganisms influence soil nutrient availability and microbial communities during fertilization is important for improving crop productivity. However, whether bio-organic fertilizers provide additional ecological benefits beyond those of conventional organic fertilizers, and the mechanisms underlying such effects, remain unclear. In this study, we combined plant growth measurements, soil nutrient analyses, high-throughput sequencing, and microbial co-occurrence network analysis to evaluate peanut responses to organic fertilizer (OF) and Bacillus subtilis-amended bio-organic fertilizer (BOF). Both OF and BOF significantly increased soil organic carbon content compared with the unfertilized control (CK) (p < 0.05). BOF further increased soil ammonium nitrogen availability and significantly enhanced root length and root dry weight compared with both CK and OF (p < 0.05). Although bacterial α-diversity did not differ significantly among treatments, fungal richness was significantly reduced under OF and partially restored under BOF (p < 0.05). Both bacterial and fungal community compositions differed significantly among treatments (p = 0.001 for both). BOF was also associated with the enrichment of potentially beneficial microbial taxa, including Azospirillum, Glomeromycetes, and Glomus, as well as distinct changes in microbial co-occurrence patterns. Overall, these findings indicate that the effects of B. subtilis-amended bio-organic fertilizer on peanut growth are associated not only with improved soil nutrient conditions but also with changes in microbial community composition and potential microbial association patterns, providing further insight into the microbiome-related effects of functional microbial fertilization.