Effects of intercropping on tea yield, quality, and soil properties: A meta-analysis

Intercropping is a traditional and sustainable agricultural practice that enhances soil fertility, reduces erosion, and promotes plant growth and metabolism. Despite widespread adoption in tea plantations, intercropping effects on yield, quality, and soil are highly context-dependent, varying with species choice, climate, and site-specific conditions. Using 157 paired observations from 41 articles, we performed a meta-analysis to quantify how intercropping affects tea yield, quality, and soil, and to determine the primary modulating factors. Across all included reports, intercropping significantly increased tea yield by 11.9%. It also elevated the levels of free amino acids (AAs) by 19.08% and reduced the levels of tea polyphenols (TPs) by 7.16%, leading to a notable decrease in the TP/AA ratio, which is associated with tea quality. Additionally, intercropping increased soil nutrient levels and soil pH. Initial organic matter and pH had a significant influence on tea yield and quality outcomes, while the type of plants used for intercropping and climatic factors such as mean annual temperature and mean annual precipitation were closely associated with improvements in soil quality. Overall, intercropping can improve tea yield and quality while enhancing soil conditions in tea plantations, although the magnitude of these benefits depends on companion crop selection, soil status, and climate.