Effects of Pueraria montana and Melastoma dodecandrum Intercropping on Soil and Tea Plant Growth in Terraced Tea Gardens: A Sustainable Agricultural Practice

Tea, a predominant economic crop in China, often thrives on terraced fields, but the long-term monoculture practiced in these terraced tea gardens has led to soil degradation, adversely affecting tea tree growth. Intercropping offers a sustainable solution, but its specific effects on soil and tea trees remain unclear. This study investigated the complex interactions between soil microorganisms, soil, and tea trees in two intercropping systems: tea/ Pueraria montana var. culaishanensis (HWT) and tea/ Melastoma dodecandrum Lour. (YP). The results showed that both intercropping modes significantly improved bud density, hundred-bud weight, and yield, thereby promoting tea tree growth. HWT significantly increased soil porosity, organic matter, available N, and available P in tea garden soils, while YP significantly increased soil porosity, organic matter, available P, and available K, all of which improved soil conditions. Both intercropping modes also affected the diversity and richness of bacterial communities and the community structure at the phylum level. Microbial co-occurrence network and topological characteristics analysis further indicated that the soil microbial community structure under intercropping was more intricate and tightly connected. Linear discriminant analysis effect size analysis demonstrated that beneficial microbial groups were significantly higher under both intercropping modes compared with monoculture tea plantations. Moreover, both intercropping modes promoted the C and N cycles in the soil, significantly enhancing microbial functions related to cellulolysis. In conclusion, both intercropping modes can promote tea tree growth, improve soil physical and chemical properties in tea gardens, increase beneficial microbial groups, and positively affect soil microbial community structure and function. However, HWT has a greater impact on functional microorganisms related to C and N cycles, especially N cycling. Therefore, intercropping with suitable slope-protection crops provides a potential solution for the sustainable development of terraced tea gardens, offering strong support for the construction of green and environmentally friendly tea gardens.