Oats Intercropping and Biochar Amendment Modify Soil Nutrients and Microbiota Structure to Enhance the Quality of Continuous Cropping Peppers

To promote sustainable cultivation and soil health in agriculture, urgent strategies are needed to address the challenges posed by continuous cropping for high-quality pepper production. This study investigated the impact of oats incorporation and biochar amendment in a 12-year continuous pepper cropping system. Compared with the pepper monoculture system (CK), the combination treatment of intercropping with oats and biochar amendment (T1) significantly increased the soluble solids content by 3.13% and the β-carotene content by 8.83-fold in pepper fruits ( P < 0.05). The soil pH under intercropping with oats or biochar modification was comparable to that of the CK. Notably, lower soil bacterial operational taxonomic units were observed under this treatment, and soil bacterial diversity decreased consistently with pepper development, regardless of the cultivation system. In contrast, fungal diversity exhibited fluctuations under the companion oat/biochar condition, with fungal community patterns modulated throughout the pepper development process ( P < 0.05). Dominant microbes such as Sphingomonas , Pseudomonas , Chrysosporium , Mortierella , and Cladosporium were identified in continuous cropping pepper soils. Kyoto Encyclopedia of Genes and Genomes metabolic profiling revealed significant effects of the cultivation type on the metabolic pathways of functional genes in soil microbial communities. Overall, the practice of planting oats and using biochar in the soils of continuously cropped pepper fields is feasible and sustains the pepper industry as an agroecosystem.