Intercropping reduces soil erosion, improves soil conditions, and increases productivity of a Camellia oleifera plantation

Background and aims Camellia oleifera, a tree species of significant ecological interest and economic value, is widely cultivated in China for its oil production. However, many C. oleifera plantations, particularly in the red soil regions of the Yangtze River Basin and southern China, show low productivity due to soil quality limitations. We hypothesized that intercropping would reduce soil erosion, improve soil conditions, and increase C. oleifera productivity. Methods To test this hypothesis, we intercropped C. oleifera with three herb species, Parthenocissus tricuspidata, Coreopsis lanceolata, and Mentha haplocalyx, in subtropical Hunan. Results Compared with monoculture, intercropping reduced runoff by 33.9–51.4%, soil loss by 72.4–84.3%, total nitrogen loss by 34.4–56.9%, and total phosphorus loss by 48.0–60.1%. Intercropping also modified soil microbial community composition, enhancing alpha diversity and promoting beneficial taxa such as Acidobacteria (31–116%) and Verrucomicrobia (15–820%). Furthermore, intercropping increased soil organic carbon by 7.4–53.8%, soil phosphorus by 2.3–56.4%, and soil urease activity by 40.4–86.0%. Most importantly, intercropping increased C. oleiferaproductivity, with the C. oleifera - Parthenocissus tricuspidata treatment yielding the highest total fruit production (134% greater than the control) and the highest total oil yield (157 kg ha⁻¹). Conclusions These findings support our hypothesis and demonstrate that intercropping is a sustainable land management practice for mitigating soil erosion, enhancing soil health, and boosting productivity in agroforestry systems.