Effects of different mixed forage species and ratios in legume-grass mixtures on promoting soil organic carbon accumulation in the western mountain of Sichuan

To establish artificial grasslands by intercropping Trifolium repens or T. pratense with Dactylis glomerata and Lolium perenne with the three sowing ratios L₅G₅ (5 ꞉ 5), L₄G₆ (4 ꞉ 6), L₃G₇ (3 ꞉ 7) this study investigated the impact of intercropping legumes and grasses on soil organic carbon and its components in the mountains of southwest Sichuan. The study compared and analyzed the variations in soil organic cabon (SOC) and its components in soils under different legume-grass species and ratios, to identify optimal combinations for promoting soil organic carbon accumulation. Compared with the mixture of T. repens, the mixture with T. pratense demonstrated a close relationship with SOC and recalcitrant organic carbon. The soil mixture containing T. pratense in 0 – 30 cm had higher heavy fraction organic carbon (HFOC) content and β-glucosidase (BG) activity (P < 0.05). Additionally, the 15 – 30 cm layer of the soil containing T. pratense showed higher polyphenol oxidase (PPO) activity (P < 0.05). The highest levels of SOC and its components, and BG and PPO activities, were observed at the intercropping ratio of 4 ꞉ 6. Therefore, for the accumulation of soil organic carbon it is beneficial to select T. pratense mixed sowing with L. perenne and D. glomerata at 2 ꞉ 2 ꞉ 1 in the southwest mountain of Sichuan.