Intercropping With Green Manure Regulates Microbial Community Structure and Improves Tea Quality by Changing Soil Available Nutrients Under Organic Management

Intercropping with green manure is recognized as a sustainable and ecological agricultural practice that regulates soil microbial activity and promotes plant growth. Despite its potential benefits, the impact of tea plants intercropping green manure on organic plantations remains largely unexplored. This study primarily evaluated the effects of intercropping summer green manure and winter green manure (TSR: tea intercropping soybean + ryegrass; TMR: tea intercropping mung bean + radish; TSC: tea intercropping soybean + common vetch; TM: tea plant monoculture, consider as control) on soil microbial community composition, tea quality, and bacterial function in an organic tea plantation. Relative to TM, TMR improved soil physical structure by decreasing the soil penetration resistance and bulk density by 30.4% and 9.30% (p < 0.05), thus creating a conducive environment for microbial growth and activity. The composition and beta diversity of microbial communities have markedly differed after intercropping, attributed to changes in soil available nutrients, enzyme activities, and soil compaction. Intercropping increased the relative abundance of key microbial phyla, including Acidobacteriota, Firmicutes, Chytridiomycota, and Rozellomycota. Notably, TSR and TSC enhanced nitrogen fixation function by enriching beneficial microorganisms, such as Bradyrhizobium and Clostridium_beijerinckii, which were mediated by soil available potassium. The content of amino acids in tea leaves was increased by 20.2% under TMR. The partial least squares path model further revealed that intercropping with green manure improved tea quality by decreasing soil penetration resistance and increasing soil available phosphorus. Overall, intercropping with green manure can effectively reshape the microbial community and improve tea quality by affecting the soil environment, underscoring the importance of adopting intercropping strategies in organic plantations.