Haymaker, Joseph R.2024-11-122024-11-122024-11-11vt_gsexam:41567https://hdl.handle.net/10919/121586This research investigated the long-term effects of transitioning from intensive tillage to no-till (NT) practices with cover crop (CC) incorporation on soil quality, agronomic performance, and economic returns in Virginia's Coastal Plain. Nine years after integrating NT practices and CCs, improvements in soil physical and chemical properties were observed, including a 22% to 65% increase in soil organic matter (SOM) in the top 5 cm, a 4% reduction in bulk density, and enhanced soil moisture retention in corn production. Timing of CC termination played a crucial role in optimizing biomass production and nutrient accumulation. Overall accumulation rates were 44.4 kg dry biomass ha-1 d-1, 1.22 kg N ha-1 d-1, 0.16 kg P ha-1 d-1, 1.36 kg K ha-1 d-1, and 0.08 kg S ha-1 d-1 of delayed termination between March 15 and April 30. Each additional day of cover crop growth contributed to a fertilizer value of $3.91 ha-1, highlighting the economic advantage of extending CC growth during this critical period. In 2023, CC effects on corn N fertilizer demand and yields were assessed by applying variable N rates of 0, 56, 112, and 168 kg N ha-1 at sidedressing. Greatest corn yields at each N rate were observed following hairy vetch and a vetch-dominant CC mix, which had low C:N ratios (≤12:1) and accumulated 134 to 186 kg N ha-1 in their aboveground biomass. Corn yields after these CCs were 8.5 to 9.3 Mg ha-1 at the zero N sidedressing rate, increasing to 10.8 to 11.3 Mg ha-1 at the 168 kg N ha-1 rate. However, increasing the N rate yielded minimal economic benefits for these treatments. Vetch treatments produced the highest net returns, with greater returns at lower N rates, as vetch generated an additional US$1,012 ha-1 at the zero N sidedressing rate compared to the no CC control. Conversely, cereal rye produced a negative net return across all N rates, with positive returns achievable only with state cost-share payments. The findings underscore the importance of adaptive N management strategies and policy adjustments to support environmentally and economically sustainable cover crop practices in corn production.ETDenIn CopyrightSoil Organic MatterNutrient CyclingCoastal Plain SoilsSoil QualityAdaptive Nitrogen ManagementDissertation