Synergistic effects of Bacillus spp. and graphene oxide on nutrient cycling and soil health in peach tree rhizospheres

Introduction Peach trees are often threatened by various diseases during cultivation. Methods This study took the roots and rhizosphere soil of diseased peach trees as the research objects and investigated the effects of single and combined treatments of Bacillus (including Bacillus velezensis and Bacillus subtilis ) and graphene oxide (GO) on peach trees. Results The results showed that compared with the diseased control group, the single treatments of Bacillus velezensis (Group V) and Bacillus subtilis (Group S) significantly reduced soil pH (to 8.55 and 8.35, respectively) as well as the contents of calcium (Ca) and zinc (Zn), enhanced organic carbon accumulation (up to 26.43 g/kg), bringing these key indicators close to the rhizosphere levels of healthy peach trees (CK1: pH 8.42, organic carbon (OC) 24.10 g/kg). Additionally, these treatments restored nutrient cycling functions by increasing microbial diversity. The effect of GO treatment showed a concentration dependence: high-concentration GO increased the microbial Shannon index and available phosphorus content, while low-concentration GO inhibited the accumulation of available nitrogen. Among the combined treatments, the combination of Bacillus velezensis and GO, by synergistically regulating the contents of Ca and available nitrogen, restored rhizosphere microecological homeostasis more significantly than the combination involving Bacillus subtilis . Discussion This study reveals the mechanism by which the “microbe-GO” combination achieves rhizosphere ecological remediation through the “element balance - microbial community function” linkage and provides a theoretical basis and technical strategies based on healthy microecological targets for the prevention and control of soil-borne diseases in peach trees.