Synergistic Bacillus-woody peat bio-composting enhances dissolved organic matter transformation and cucumber growth

Woody peat is a valuable soil amendment, with its enhancement primarily relying on physical and chemical methods while biological treatment remains limited. This research investigated the biological compost of woody peat mediated by plant growth-promoting rhizobacteria (PGPR) strain Bacillus velezensis SQR9. The composted woody peat significantly increased cucumber biomass and height by 27-37 %, with dissolved organic carbon increasing 18.9-fold (to 69.61 mg/L) and humic acid content rising 3.7-fold (to 27.40 %). The relative abundance of Bacillus increased from undetectable level to 12.15 %. FT-ICR MS analysis revealed that 51.67 % of initial dissolved organic matters (DOM) underwent decomposition with formation of more bioavailable compounds. Network analysis revealed intricate correlations between microbial community and DOM subcategories, highlighting roles of key bacteria like Bacillus, Streptomyces and Thermosporothrix in DOM transformations. Moreover, sterilized treatment in plant experiments confirmed beneficial substances, rather than PGPR, played the dominant role in plant growth promotion. This study obtained a biofertilizer enriched with beneficial bacteria and humic acids, offering an environmentally sustainable approach to woody peat utilization in sustainable agriculture.