The primary mechanism through which organic amendments enhance the nodulation ability of leguminous crops involves increasing the content of available phosphorus (AP) in the soil. Despite this, the role of plant rhizosphere microbial communities has not been fully appreciated. This study investigated the impact of different fertilization treatments, including a no-fertilizer control group (CK), a chemical nitrogen–phosphorus–potassium treatment group (NPK), and a group treated with both organic manure and chemical NPK (NPKM), on the structure of microbial communities in the peanut rhizosphere and their nodulation ability using high-throughput sequencing technology, co-occurrence network analysis, and structural equation modeling. The peanut nodule count increased significantly on organic manure plus NPK application, ranging from 2.26 to 2.50 times that of the CK treatment group. Under NPKM treatment, the diversity of bacterial and rhizobial communities in the peanut rhizosphere significantly improved. Co-occurrence network analysis showed that the peanut rhizosphere microbial co-occurrence network under NPKM treatment was more complex. Additionally, the ecological importance of rhizobial groups within the network significantly increased. Further analysis of the interaction patterns between different microbial groups revealed that under NPKM treatment, the positive correlation ratio between arbuscular mycorrhizal fungi (AMF) and rhizobia (RPAR) was significantly higher than that in the CK and NPK treatment groups. Structural equation modeling (SEM) analysis demonstrated that the RPAR significantly enhanced peanut nodulation ability, an effect that was positively modulated by AP. In summary, this study highlights the potential key role of the synergistic action between rhizobia and AMF in influencing the nodulation process of leguminous plants and provides a scientific basis for the effective management of plant microbial communities.

Soil fungi play a pivotal role in maintaining ecosystem functions and regulating plant health. Although plant root traits can significantly impact the abundance and diversity of different fungal groups, the mechanism by which plant root strategies drive the assembly of soil fungal guilds remains limited. Utilizing Root Economics Space theory, this study investigates how four green manures (hairy vetch, rye, radish, and rapeseed) with contrasting root functional strategies (along the ‘fast–slow’ and ‘outsourcing–DIY’ axes) regulate the composition and functional structure of soil fungal communities. Community characteristics of three functional guilds (plant pathogens, saprophytes, and arbuscular mycorrhizal fungi), as well as relationships between these communities and plant root traits, were evaluated using a combination of Illumina high-throughput sequencing, functional annotation, and multivariate statistical analysis. Overall, different root strategies were associated with distinct fungal community patterns, potentially related to differences in root-derived resource inputs and soil properties. The ‘slow’ and ‘DIY’ strategies were associated with lower relative abundance of plant pathogenic fungi and higher relative abundance of saprotrophic fungi, whereas the ‘fast’ and ‘outsourcing’ strategies were associated with higher relative abundance of plant pathogens and AMF. These findings suggest that root functional strategies may help explain variation in fungal guild composition under different green manure species. From a practical perspective, the results provide a basis for selecting green manure species to help manage soil-borne disease risk, regulate beneficial soil microbial communities, and support more sustainable soil management in agricultural production.