The Impact of Organic Fertilizer Substitution on Microbial Community Structure, Greenhouse Gas Emissions, and Enzyme Activity in Soils with Different Cultivation Durations

To address soil degradation risk caused by the long-term application of organic and nitrogen fertilizers in facility vegetable fields, this study selected soils with cumulative cultivation durations of 1, 3, 6, and 9 years to investigate the impact of organic and nitrogen fertilizer (OFN) application ratios on soil microbial community structure, greenhouse gas emissions, and enzyme activities. The results show that SOC content increases with soil cultivation duration and the proportion of organic fertilizer applied. Organic fertilizer stimulates urease and catalase activities; however, NH 4 + -N in the soil inhibits enzyme activities. Organic fertilizer increases the abundance of Proteobacteria and Bacteroidota, enhancing its potential carbon sequestration capacity and also resulting in higher CH 4 and CO 2 emissions. The microbial community structure is influenced by both fertilizer ratios and soil cultivation duration. As the taxonomic level becomes finer, the number of differential species at the phylum (3), class (3), order (6), family (8), and genus (8) levels increases. The highest Chao1 index in soils of 1, 3, 6, and 9 years was observed at 0%, 25%, 50%, and 75% organic fertilizer substitution ratios, respectively. The 25% organic fertilizer substitution ratio showed better microbial diversity and evenness in 3-, 6-, and 9-year-old soils.