Impact of Organic Fertilizer Substitution on Soil Quality and Microbial Diversity in Maize Ecosystems

This study addresses the global issue of soil degradation and the decline in soil quality caused by excessive fertilizer use. Field experiments were conducted in the Northeast Black Soil Region and the North China Plain to evaluate the potential of organic fertilizer as a substitute for chemical fertilizers. Four treatment groups were established: control with no fertilization (CK), pure chemical fertilizer (T0), 25% organic fertilizer substitution (T25), and 50% organic fertilizer substitution (T50). The study systematically analyzed changes in soil physical and chemical properties, organic carbon fractions, microbial communities, and maize yield. The results showed that organic fertilizer substitution significantly reduced soil bulk density and pH, while increasing available phosphorus, potassium content, and various active organic carbon components (DOC, MBC, POC, ROC) by 28.21%–52.97%. The T25 treatment resulted in a 194.1% and 30.17% increase in carbon pool management index and activity index, respectively, while also promoting microbial diversity and the abundance of functional microbial groups. Nitrogen fertilizer utilization efficiency increased by 17.95%–33.33%, and maize yield traits were significantly optimized. In conclusion, 25% organic fertilizer substitution is the optimal ratio for improving soil quality, microbial activity, and maize yield.