Production and Subsequent Application of Different Biochar-based Organic Fertilizers to Enhance Vegetable Quality and Soil Carbon Stability

This study was to elucidate the dual roles of biochar-based organic fertilizers in enhancing plant growth in intensive vegetable fields. A compost experiment and subsequent field trials were conducted. In the compost experiment, rice straw biochar, rice husk biochar, or grapevine biochar were added to cattle manure (at a 12% ratio) to produce mature compost.An experiment in which biochar-based organic fertilizer (5 t hm^–2 fresh weight) was applied to fields cultivated with leafy vegetables was performed. The findings indicated that the total carbon content, pH, and N+P₂O₅+K₂O content were 29.3–31.2%, 7.4–7.6, and 5.4–7.3%, respectively, in the final compost products. These results conformed to the biochar-based organic fertilizer standard (NY/T 3618-2020), indicating that the products could be classified as biochar-based organic fertilizers. Comparatively high nutrient content was observed in the straw biochar-based organic fertilizer. The addition of straw biochar and husk biochar to the biochar-based organic fertilizers increased the vitamin C content in the plant leaves by 12.8–29.9% and 7.0–26.8%, respectively, and in the petioles by 2.6–9.8% and 3.0–8.1%, respectively. The three types of biochar-based organic fertilizers influenced soil properties by elevating the pH, decreasing the EC by 16.9–31.8%, and reducing the available potassium by 14.6–17.9%. They also enhanced soil organic content and recalcitrant carbon content by 3.3–9.8% and 4.7–6.6%, respectively. The 12% biochar-amended compost proved to be an effective fertilizer, and its subsequent field application was also viable. This study enhances the understanding of biochar-based organic fertilizer applications for improving vegetable quality and soil organic carbon sequestration, providing scientific support for sustainable agricultural practices.