Microbial community structure and carbon–nitrogen coupling mechanisms in mixed silage of oats and forage peas in corral of the Qinghai-Tibet Plateau

Seasonal forage shortages pose a significant challenge to livestock production on the Qinghai-Tibet Plateau. To address this issue, this study developed an integrated land utilization strategy combining “cultivation + on-site ensiling” using mixed oats and forage peas. The research evaluated how different mixed-cropping ratios and lactic acid bacteria (LAB) inoculation affect silage production in this high-altitude region. In silage grown in corral plots, the 1:1 oat-pea ratio showed clear advantages over monocropped oats, increasing crude protein by 29.43% while reducing acid detergent fiber (ADF) by 14.37% and neutral detergent fiber (NDF) by 11.21%. LAB inoculation improved the fermentation quality of corral-grown silage. In inoculated oat silage, the relative abundance of Lactiplantibacillus increased significantly to 66.54%, which suppressed spoilage bacteria (e.g., Hafnia-Obesumbacterium) and reduced the ammonia nitrogen-to-total nitrogen ratio by 15–20%. When the mixed sowing ratio of oats to peas is 1:1, it minimizes dry matter loss among corral-grown silages. LAB inoculation increased propionic and acetic acid production by 25%. Metabolic prediction indicated that LAB inoculation increased nitrogen compound degradation by 17% and stimulated secondary metabolite synthesis. Bacterial communities correlated with soluble carbohydrate and lactic acid levels, whereas fungal communities regulated fiber breakdown. Redundancy analysis showed that fiber content explained over 50% of fungal community variation in corral silage. The 1:1 oat-pea ratio with LAB inoculation optimizes silage production specifically for corral systems, achieving carbon–nitrogen balance and microbial synergy. This corral-based approach provides a sustainable solution for alpine livestock resilience, transforming underutilized confinement areas into high-quality forage resources.