Quantifying the effects of conservation practice implementation on predicted runoff and chemical losses under climate change

The Soil and Water Assessment Tool with downscaled weather data generated using the MarkSim weather file generator was used to evaluate the impact of long-term conservation practice implementation on runoff, sediment, atrazine, nitrogen (N) and phosphorus (P) losses in an agricultural watershed located in northeastern Indiana. As part of the Conservation Effects Assessment Project, evaluation of these conservation practices is required to provide insight on how their implementation is benefiting the environment. The results indicate that individual conservation practices were effective in reducing a particular pollutant load, but combined practices were more effective in reducing multiple pollutant loads simultaneously. Of the individual best management practices (BMPs) assessed, no-till was the most effective in reducing multiple pollutant loads (reduced surface runoff by an average of 25%, sediment by 46%, atrazine by 46%, total N by 9%, soluble P by 16%, and total P by 29%). When BMPs were combined, pollutant load reductions were increased significantly (at α=0.05) for all pollutants, both under baseline and future climate scenarios. The reductions in runoff and pollutant loads for each decade of future climate ranged from 15 to 25% for surface runoff, 32–68% for sediment loss, 37–60% for atrazine loss, 5–13% for soluble N loss, 12–35% for total N loss, 9–41% for soluble P loss, and 33–60% for total P loss.