Projected Cover Crop Performance in the Midwestern U.S. Improves in Response to Climate Change

Abstract:

Excess nutrient runoff from agricultural areas in the Midwestern U.S. has become a grand challenge of environmental management, with negative impacts to inland and coastal water bodies (e.g., Lake Erie and the Gulf of Mexico) reaching unprecedented levels in recent years. Nutrient runoff is greatest during wet weather and is likely to be exacerbated by climate change, which is projected to bring intense warming and increased precipitation in winter and spring, leading to increased surface runoff. Conservation practices, particularly winter cover crops, can reduce nutrient loss from Midwestern agricultural watersheds, as demonstrated with short-term observed data. But performance of cover crops in response to long-term climate variability and climate change projections has been unclear. Using calibrated SWAT simulations for two small (< 2600 ha) agricultural watersheds in Indiana, long-term meteorological driving data sets from 1915-2013, and long-range climate change projections from the Indiana Climate Change Impacts Assessment, our results show that the effectiveness of cover crops increases under climate change scenarios, producing greater percent reductions in nitrate and soluble reactive phosphorus export in comparison with retrospective simulations of historical conditions. These results demonstrate that incentives that facilitate increased cover crop coverage will likely reduce nutrient pollution under the current climate, and also in the future, as the Midwest climate warms and becomes wetter in winter and spring. If implemented widely, cover crops may increase the climate resilience of the Midwestern agroecosystem, though further testing is needed at these larger spatial scales.