Microbial inoculants enhance walnut yield and soil health

The walnut industry faces sustainability challenges from declining yield and quality, exacerbated by environmental stressors and soil microbial imbalances. Microbial inoculants can boost crop growth, quality, and stress resistance, but their mechanisms—such as soil modification, pathogen suppression, and microbial community regulation—for enhancing yields require further clarification. In this study, we utilized Illumina MiSeq high-throughput sequencing technology to investigate the effects of conventional chemical fertilizers and microbial agents (Bacillus amyloliquefaciens SDTB009) on disease suppression, soil parameters, microbial communities, as well as walnut yield and quality. The results showed that the implementation of SDTB009 agent as a rhizosphere soil treatment led to notable enhancements in various soil parameters. These included increased levels of soil organic matter, total nitrogen, available potassium, soil microbial biomass carbon and nitrogen, as well as heightened activity of soil urease, alkaline phosphatase, catalase, and sucrase enzymes. Furthermore, the application of SDTB009 promoted the enrichment of Bacillus spp. and Sphingomonas spp., and significantly reduced the abundance of Alternaria spp. and Fusarium spp., concomitantly enhancing walnut yield, quality (the oil content increased by 1.33 %, the total amino acid content increased by 3.58 %, and the total protein content increased by 0.57 %) and fatty acids content. At the same time, it shows that beneficial microorganisms could positively regulate plant growth by improving nutrients and inducing disease resistance signals. This work highlighted the potential of microbial biofertilizers to simultaneously enhance soil health and agroecosystem productivity.