The symbiotic relationship between cover crops and soil microorganisms is closely linked to nutrient cycling and crop growth within agroecosystems. However, how cover crops with different root functional traits influence soil microbial communities, soil properties, and crop yields has remained understudied. This study assessed the root traits of hairy vetch (HV) and rapeseed (RP), along with soil properties, sweet potato yield, and microbial enzyme activity under red soil dryland conditions. High-throughput sequencing was also employed to characterize the diversity, composition, and network structure of soil bacterial and fungal communities. According to the plant economic spectrum theory and our research results on plant root traits, HV can be identified as a resource-acquisitive cover crop, and RP treatment can be identified as a resource-conservative cover crop. Although RP treatment did not significantly increase the sweet potato yield, the increase rate reached 8.49%. Resource-conservative cover crops were associated with increased pH, SOC, and TP, which enhanced bacterial species diversity and boosted the populations of Chloroflexi and Alphaproteobacteria. In contrast, resource-acquisitive cover crops promoted the proliferation of Gammaproteobacteria. Network analysis indicated that resource-conservative cover crops facilitated network complexity through intensified intra-community competition. Resource-acquisitive cover crops enhanced the stability of microbial communities. Collectively, these findings underscore the distinct advantages of cover crops with varying root functional traits in shaping soil microbial communities. Appropriate cover crop rotations can effectively regulate microbial communities and hold the potential to enhance crop yield.

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.

In the past ten years, in paddy rice systems in southern China, the co-incorporation of Chinese milk vetch (MV) and rice straw (RS) has become a new and effective practice in which the advantages of the two species are combined to improve rice yields. However, more studies are needed to better understand the mechanisms by which rice productivity is improved through this practice. In this study, a pot experiment was performed to investigate the effects of different residue management treatments on rice productivity and soil properties. Five treatments were tested: (i) CK (no residue and no chemical fertilizer); (ii) CF (chemical fertilizer); (iii) FM (CF with MV returning); (iv) FR (CF with RS returning); and (v) FMR (CF with a mixture of MV and RS returning). The results showed that the application of MV and/or RS returning improved grain yields by between 13.7% and 31.5%, compared with CF treatment alone. In addition, the application of MV significantly improved rice yield relative to RS returning. However, co-incorporation of MV and RS resulted in the highest yield productivity of all. FMR treatment significantly increased shoot biomass and shoot N, P, and K uptake, compared with FR treatment, at all three growth stages, and compared with FM treatment at the jointing and maturity stages. Moreover, FMR treatment significantly improved grain N, P, and K uptake, relative to FM and FR treatments. These results clearly demonstrated that co-incorporation management promotes nitrogen and phosphorus nutrient uptake at jointing and maturity stages of the rice growth process, compared to application of single residues alone, resulting in higher rice yields. Because incorporation of MV and/or RS increases the available nutrients in the soil and enhances nutrient uptake by the crop, wide-scale adoption of the co-incorporation of residues would significantly increase rice yields and improve soil fertility.

Understanding how functional microorganisms influence soil nutrient availability and microbial communities during fertilization is important for improving crop productivity. However, whether bio-organic fertilizers provide additional ecological benefits beyond those of conventional organic fertilizers, and the mechanisms underlying such effects, remain unclear. In this study, we combined plant growth measurements, soil nutrient analyses, high-throughput sequencing, and microbial co-occurrence network analysis to evaluate peanut responses to organic fertilizer (OF) and Bacillus subtilis-amended bio-organic fertilizer (BOF). Both OF and BOF significantly increased soil organic carbon content compared with the unfertilized control (CK) (p < 0.05). BOF further increased soil ammonium nitrogen availability and significantly enhanced root length and root dry weight compared with both CK and OF (p < 0.05). Although bacterial α-diversity did not differ significantly among treatments, fungal richness was significantly reduced under OF and partially restored under BOF (p < 0.05). Both bacterial and fungal community compositions differed significantly among treatments (p = 0.001 for both). BOF was also associated with the enrichment of potentially beneficial microbial taxa, including Azospirillum, Glomeromycetes, and Glomus, as well as distinct changes in microbial co-occurrence patterns. Overall, these findings indicate that the effects of B. subtilis-amended bio-organic fertilizer on peanut growth are associated not only with improved soil nutrient conditions but also with changes in microbial community composition and potential microbial association patterns, providing further insight into the microbiome-related effects of functional microbial fertilization.