Long-term effects of cover crops and no-tillage on soil health in the Virginia Coastal Plain

Abstract

After centuries of conventional tillage practices, sandy loam Coastal Plain soils have been heavily degraded, resulting in severely depleted soil organic carbon (SOC) stocks. This study examined impacts on soil health when transitioning from intensive tillage in vegetable production to no-till (NT) corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production with cover crops (CC). A long-term cropping system experiment, established in 2014, assessed twelve different crop rotations, including a conventionally tilled (CT) fallow control and various CC treatments, ranging from monocultures to a perennial mixture with corn planted every third year. After nine years, CC treatments increased near-surface SOC concentrations (8.4–10.5 g kg⁻¹ at 0–5 cm) and SOC stocks (4.6–7.3 Mg ha⁻¹) compared to fallow controls (6.4–6.9 g kg⁻¹; 4.6–5.2 Mg ha⁻¹). Soil organic carbon gains were most pronounced in the surface 5 cm and had a positive relationship with cumulative C inputs (R² = 0.38). Cover crops reduced bulk density by up to 11 %, and SOC stocks were still significantly greater than fallow treatments as SOC concentration gains offset the lower bulk density. Treatments with hairy vetch (Vicia villosa Roth L.) or legume-dominant CC mixes lowered soil pH compared to fallow or grass-based CC treatments, potentially increasing the need for lime applications. Adoption of NT alone, without CCs, did not deliver similar soil health benefits. These results highlight the importance of integrating CCs into crop rotations to enhance SOC and improve soil physical properties in degraded Coastal Plain soils.