Abstract:Paddy soil has many kinds and large quantities of microbes, which will drive soil organic carbon mineralization and hold organic carbon pool. In this study, the paddy fields in Fuzhou Plain were used as test plots, and three kinds of treatments, such as biochar, slag, and biochar+slag, were applied to determine the effects of applied treatments on soil physical and chemical properties, microbial quantity, and organic carbon content in paddy fields, and the microbial role in the stabilization of soil carbon pools. The results showed that:(1) The application of slag and biochar could increase the quantity of microbes in paddy soil and the ratio of fungi/bacteria in soil, which was beneficial to the stability of soil carbon pool, and the effect of mixed treatments was more significant. (2) The three application treatments significantly increased the quantity of fungi and fungi/bacteria ratio in early rice jointing stage, and the fungi/bacteria ratio increased by 0.016, 0.015, and 0.018, respectively. The bacteria quantity was increased significantly. The single application and mixed treatments of biochar increased the quantity of aerobic bacteria in late rice jointing stage. The mixed application treatment significantly increased the quantity of aerobic bacteria in early maturity (p<0.05). (3) The slag application treatment significantly increased the soil DOC content in the early rice maturity stage, and the biochar application treatment significantly increased the soil SOC content in the early rice maturity stage. The mixed application treatment significantly increased the soil SOC content in the early rice jointing stage. Soil DOC significantly increased in the late rice jointing stage (p<0.05).The content of organic carbon in the early and late rice jointing stage was significantly higher than that in the maturitystage. (4) The physical and chemical properties, microbial quantity, and organic carbon content of paddy soils were positively affected. The soil of early paddy soil was significantly negatively correlated with soil MBC content, and it was significantly positively correlated with the quantity of fungi (p<0.01). The soil moisture content of late rice was positively correlated with DOC, aerobic bacteria, facultative anaerobic bacteria, and fungi. There was a significant negative correlation between MBC and anaerobic bacteria (p<0.05).