Marali, Kalra, Department of Civil & Environmental Engineering, Penn State University, 235 Agricultural Engineering Building, University Park, PA 16802, mmk5750@psu.edu; Cibin, Raj, Department of Civil & Environmental Engineering, Penn State University, 247 Agricultural Engineering Building, University Park, PA 16802, czr58@psu.edu.
The Susquehanna River is one of the main contributors to the ongoing water quality problem in the Chesapeake Bay, making agricultural nutrient pollution a major concern in the Susquehanna River Basin (SRB). Agricultural best management practices such as cover cropping are instrumental in reducing nutrient loads to the Bay. However, cover crop implementation remains low in the SRB. Farmers may not be motivated to bear the cost of downstream water quality improvements if the recommended best management practices seem to have no benefits for their farms and communities. We used the Soil and Water Assessment Tool to model seven scenarios of improved or expanded cover cropping practices in the SRB, evaluating each scenario’s impact on six ecosystem services: water quality, crop yield, hay yield, soil erosion regulation, nutrient cycling, and water cycling. We found that increasing the area under cover crops led to small increases in crop yield, thanks to a “green manure” effect where cover crop biomass decomposed into plant-available nutrients. Increases in cover cropping reduced sediment and nutrient loads at the SRB watershed outlet, but without corrected fertilizer application rates, summertime water quality actually worsened. Leguminous cover crops were more successful at preventing soil loss, while grain cover crops were more effective at reducing nitrogen loss. Harvesting cover crops, known as commodity cover cropping, allowed for the production of a small hay crop in the same year as a cash crop, but neutralized the green manure effect. Extending the cover crop season with early planting and late termination increased the soil and water ecosystem service benefits of cover cropping, but reduced cash crop yield. These results show that expanded cover cropping in the Susquehanna River Basin can improve downstream water quality while reducing soil loss and improving soil fertility in the fields where it is implemented.
cover crop, ecosystem services, Susquehanna River, hydrological modeling