Effects of soybean–tea intercropping on soil-available nutrients and tea quality

Plant intercropping is increasing in popularity, is conducive to plant growth and development and can improve plant quality and yield. In this study, we intercropped tea (Camellia sinensis) cv. ‘Su cha zao’ and soybean (Glycine max) cv. ‘Lamar’ in a tea plantation. The chlorophyll content was higher in intercropped tea leaves than in monoculture, and the different phenotypic characteristics of intercropping and monoculture were correlated with chlorophyll and carotenoid content. Our analyses showed that soybean–tea intercropping not only alleviated cold damage, but also influenced tea plant growth. Furthermore, the soil ammonium nitrogen (N) in intercropping mode increased during soybean flowering and mature periods and was highest in the soybean flowering and podding period. Catechin levels in tea leaves significantly decreased, and the amino acid and soluble sugars increased, for intercropped compared with monoculture tea leaves. The analysis of soil fertility and tea leaf physiological indices also indicated that N fertiliser was significantly positively correlated with free amino acids in tea leaves. In conclusion, soybean–tea intercropping affected the effective N content in soil, especially ammonium N, and the formation of the main physicochemical composition of tea leaves, as well as tea taste and aroma. Thus, intercropping can sustainably improve nutrient management and increase crop yield and quality.