Abstract: We examined the impacts of intercropping of tea trees with green manure on soil aggregates and organic carbon content (SOC) in tea garden with a two-year field experiment. Three treatments of tea tree intercropping with ryegrass (T1), rape (T2) and alfalfa (T3) were established, with the traditionally managed clean tea garden as the control (CK). We investigated the percentage of soil water-stable aggregates, SOC content in aggregates of different particle sizes and the stability indexes of soil aggregates (R_0.25, MWD and GMD) under different treatments. We analyzed the relationship between SOC and soil aggregate stability using the structural equation model (SEM), aiming to provide a scientific basis for improving soil quality. The results showed the proportion of aggregates with > 0.25 mm particle size and SOC content within them increased after two years of planting green manure. As soil depth increased, the SOC content of soil aggregates across various particle sizes exhibited a decreasing trend. Intercropping with green manure effectively increased the SOC content of soil aggregates with different particle sizes. In the 0-15 cm soil layer, the SOC content of 0.25-0.5 mm and 2-3 mm aggregates in T3 treatment was significantly increased by 15.56% and 26.77%, respectively (P<0.05). In the 15-30 cm soil layer, the SOC content of soil aggregates across each particle size in T1 and T3 treatments significantly differed from that in CK (P<0.05). In the 30-45 cm soil layer, the SOC content of soil aggregates across each particle size of T3 treatment were significantly increased by 4.30%-37.44% (P<0.05). The SEM analysis revealed that SOC could positively influence both formation and stability of soil aggregates. The application of leguminous green manure had stronger positive effects on the stability of soil aggregates and the enhancement of SOC content in aggregates. The intercropping mode of tea tree with green manure effectively improved the percentage content and stability of water-stable aggregates in tea garden soil, and increased the SOC content in aggregates of each particle size. These findings provide a theoretical basis for the application and promotion of tea garden intercropping green manure technology to improve soil quality.

Key words: tea tree, green manure, intercropping, soil aggregate, organic carbon