Crop Diversification Enhances Peanut Productivity Through Soil Fertility Improvement and Key Taxa Enrichment in Red Soil

Continuous monocropping and inappropriate fertilization have contributed to nutrient depletion and soil degradation, limiting peanut productivity in subtropical red soil agroecosystems. Although diversified cropping may help alleviate these constraints, the reasons why it improves peanut productivity remain unclear. In this study, we conducted a long-term field experiment in Jiangxi, China, to compare four cropping systems, assess soil nutrients, peanut productivity, and bacterial communities, and further evaluate the role of key taxa through inoculation assays and structural equation modeling. Results showed that diversified cropping improved peanut growth and yield, with the green manure integrated system performing best overall. Diversified cropping also increased soil organic carbon, total nitrogen, and available phosphorus, while reshaping bacterial communities. Several taxa, including Bradyrhizobium, Mycobacterium, Dormibacter, and Ardenticatena, were positively associated with soil nutrients. Inoculation assays further showed that a synthetic consortium assembled from representative strains affiliated with key taxa produced stronger effects on plant growth than a single-strain inoculation. Structural equation modeling identified key taxa as the factor most strongly associated with crop productivity. These findings suggest that higher peanut productivity under diversified cropping was closely associated with concurrent improvements in soil fertility and the enrichment of key taxa.