High-Residue and Reduced Tillage Enhances Soil Fertility, Weed Suppression, and Crop Yield in Organic Vegetable Systems

Organic annual vegetable farming systems often rely on intensive tillage for weed management due to the prohibition of synthetic herbicides. Regenerative organic agriculture aims to improve soil health and reduce the frequency and intensity of soil tillage by using cover crops as high-residue mulches to suppress weeds. In southern coastal California, the moderate climate supports year-round vegetable production, discouraging many growers from integrating cover crops into their operation and leaving sustainability-minded growers with few strategies to produce organic vegetables outside of reliance on tillage. This study evaluates standard organic tillage practices versus high-residue cover-crop mulch system on squash, peppers, and eggplant over two seasons. We assessed treatment effects on soil health indicators, weed pressure, and crop production. Soil under the cover-crop system improved soil organic matter, organic carbon and nitrogen, microbially active carbon, and water infiltration compared to bare soil. Weed biomass was substantially lower under the high-residue mulch due to persistent surface cover. Crop yield was 82%, 169%, and 189% higher in the cover-crop plots for squash, pepper, and eggplant, respectively. These findings demonstrate that high-residue cover-crop systems can enhance soil health, reduce weed pressure, and substantially increase yields, providing evidence-based strategies for implementing regenerative organic practices in vegetable systems.