Assessing climate change impacts on winter cover crop nitrate uptake efficiency on the Coastal Plain of the Chesapeake Bay Watershed using SWAT model

Abstract. Climate change is expected to exacerbate water quality degradation in the Chesapeake Bay Watershed (CBW). Winter cover crops (WCCs) have been widely implemented in this region due to their high effectiveness at reducing nitrate loads. However, little is known about climate change impacts on the effectiveness of WCCs for reducing nitrate loads. The objective of this study is to assess climate change impacts on WCC nitrate uptake efficiency on the Coastal Plain of the CBW using Soil and Water Assessment Tool (SWAT) model. We prepared climate change scenarios using General Circulation Models (GCMs) under three greenhouse emission scenarios (e.g., A1B, A2, and B1). Simulation results showed that WCC biomass increased by ~ 58 % under climate change scenarios, due to climate conditions conducive to WCC growth. Prior to WCC implementation, annual nitrate loads increased by ~ 43 % (5.3 kg N·ha^-1) under climate change scenarios compared to the baseline scenario. When WCCs were planted, nitrate loads were substantially reduced and WCC nitrate reduction efficiency increased by ~ 5 % under climate change scenarios relative to the baseline, due to increased WCC biomass. Therefore, the role of WCCs in mitigating nitrate loads should increase in the future given predicted climate change.