Leguminous Cover Crops Promote Microbial Community Diversity in the Rhizosphere Soil of Tea Plants: Insights from 16S rRNA Microbiome Analysis

The integration of leguminous cover cropping systems (LCR), particularly soybean (LC-S) and cowpea (LC-C), into tea agroecosystem provides a sustainable strategy to enhance soil ecosystem services by promoting beneficial soil microbial communities through the modulation of the rhizosphere microbiome in the tea rhizosphere soil. This study employs 16S rRNA gene sequencing to assess how these leguminous cover crops, when incorporated as green manure within the tea row spaces, influence the microbial community diversity in the rhizosphere soil of tea plants. Compared to conventional monoculture tea plantations (CK), the introduction of LC-S and LC-C significantly reshape the microbial communities in the tea rhizosphere soil. They promote the abundance of copiotrophic and specialized taxa such as Proteobacteria, Actinobacteria, and Mycobacterium, which are crucial for nutrient cycling and organic matter decomposition. Additionally, LC-S and LC-C enrich beneficial microbes including Chloroflexi, Bradyrhizobium, Acidothermus, and Cyanobacteria, supporting processes like nitrogen fixation and pathogen suppression. The metagenomic analysis confirms that leguminous cover crops consistently increase bacterial diversity and enrich beneficial phyla vital for soil nutrient dynamics, organic matter breakdown, and environmental stress resilience. Furthermore, microbial genera linked to nitrogen mobilization and complex organic matter degradation are promoted, underpinning the synthesis of nitrogenous compounds (such as theanine, amino acids), polyphenolic secondary metabolites (like flavonoids), and volatile organic compounds essential for tea quality. Functional pathway analyses revealed that LC-S enhances degradation pathways involved in carbohydrate and aromatic compound metabolism, augmenting precursors for key bioactive constituents such as theanine and catechins. Conversely, LC-C favors glycan biosynthesis and degradation pathways, likely improving root–microbe interactions and micronutrient uptake, both critical for polyphenol biosynthesis. Collectively, these microbiome-driven changes improve tea’s sensory qualities, including flavor, aroma, and antioxidant capacity, by enriching bioactive compounds. This microbiome-mediated agro-ecological approach offers a sustainable alternative to conventional monoculture, enhancing soil functionality, ecological resilience, and the economic viability of tea production systems.