Cover cropping and interseeding management practices to improve runoff quality from dairy farms in central Pennsylvania

Intensive agricultural activities are known to increase nutrient and sediment losses, leading to degraded water quality in receiving water bodies. In the Chesapeake Bay watershed, animal operations must reduce farm-level nutrient and sediment losses to meet federally mandated load reduction goals. This work investigated the potential water quality benefits and economic impacts of adopting post-harvest cover cropping or interseeded cover cropping on eight dairy farms representative of common operations in central Pennsylvania. The farms, simulated with the Integrated Farm System Model (IFSM), represented confined, organic, grazing, and Amish farming practices for dairy herds ranging in size from 35 to 150 lactating Holstein cows. Simulations were run for 25 years using observed weather data for Mifflin County, Pennsylvania, and for the dominant agricultural soil series in the county: Hagerstown silt loam. Model output included water balance results, nutrient and sediment loads, and farm-scale economics at an annual scale. Overall, simulation results showed that post-harvest cover cropping reduced N, P, and sediment by 18%, 17%, and 42%, respectively, while interseeding reduced loads by 49%, 41%, and 46%, respectively. Economic impacts of cover cropping and interseeding varied among farm types, but nearly all scenarios resulted in a net loss in profit compared to the baseline. However, annual economic losses were relatively minor: less than $28 ha^-1 for cover cropping and $63 ha^-1 for interseeding. Results suggest that the benefits of interseeding cover crops are greater for farms with larger portions of land in row crops with less perennial grassland. Interseeding necessitates purchasing additional equipment or custom hiring the seeding operation. These results have implications for cost-share incentive structures aimed at promoting adoption of cover crops and interseeding, especially for confined farms, which may otherwise experience financial losses if these practices are adopted.