In this investigation, the influence of organic amendment on the structural and functional dynamics of soil microbial communities and its effect on rice productivity were examined. Five fertilization treatments from a 40-year field experiment were selected： no fertilizer （CK）, inorganic NPK fertilizer （NPK）, inorganic NPK combined with green manure （NG）, inorganic NPK combined with green manure and pig manure （NGM）, and inorganic NPK combined with green manure and rice straw （NGS）. The findings revealed that the organic amendment enhanced the soil organic carbon （SOC）, total nitrogen （TN）, and total phosphorus （TP） levels, alongside an increase in rice yield； notably, the most significant improvements were observed with the NGM treatment. High-throughput sequencing highlighted that within the bacterial community, Proteobacteria （22.57%） and Nitrospirota （18.56%） dominated in abundance. The organic amendment led to a substantial shift in microbial community composition, chiefly reflected by an increase in Proteobacteria alongside a decrease in Nitrospirota. Predictive functional analyses through PICRUSt2 revealed a rise in gene abundance linked to the decomposition of organic carbon, specifically genes encoding amylase （amyA）, cellulase （bglX, bglB, and endoglucanase）, and hemicellulose-decomposing enzymes （xylA and xynA）. Additionally, there was an observed increase in the abundance of genes facilitating organic nitrogen mineralization, such as those for urease （ureA, ureB, and ureC）, glutamate dehydrogenase （gdhA）, and glutamine synthetase （aspQ）. The random forest model determined that several soil property indicators, including TP, SOC, pH, TN, and dissolved organic nitrogen, along with the composition of the bacterial community and the abundance of functional genes involved in the decomposition of organic carbon and nitrogen, significantly influenced the rice yields. Furthermore, PLS-PM analysis elucidated that the organic amendment boosted soil SOC and TP levels, which, by modifying the bacterial community's composition, augmented the relative abundance of genes associated with the breakdown of organic carbon and nitrogen. This process facilitated nutrient cycling, culminating in elevated rice production.
Keywords: bacterial community structure; function genes; organic matter amendment; red paddy soil; rice yield.