Replacement of Corn by Perennial Cellulosic Bioenergy Crops on Sloping Farmland: Implications for Water Quality and Economic Benefits

Perennial cellulosic bioenergy crops have the potential to control nutrient losses from agriculture while providing biomass for biofuel production. This study employed a rigorously calibrated Soil and Water Assessment Tool (SWAT) model to assess the effects of replacing conventional corn ( Zea mays L.) with Miscanthus × giganteus and Alamo switchgrass ( Panicum virgatum L.) on nitrogen (N) and phosphorus (P) losses across three slope categories (<2%, 2%–4%, and >4%) within the Upper Mississippi River Basin (UMRB), a typical Mollisol region with intensive agricultural production. Model results indicated that N and P losses were effectively reduced by replacing corn with two bioenergy crops in 1984–2018. Organic P loss, dissolved inorganic P loss, and nitrate N (NO 3 ‐N) loss by runoff were reduced by an average of over 93%, with more significant reductions occurring at higher slopes. NO 3 ‐N leaching was reduced in most zones. Notably, replacing corn with Miscanthus and switchgrass achieved economic benefits from biofuel production of 3,000–6,000 US$/ha and environmental benefits from savings in pollution‐control costs of approximately 2,700 US$/ha. By a trade‐off analysis between environmental and economic benefits, Miscanthus was suitably planted in the western and downstream zones of the basin with single and double harvesting, and switchgrass was suitably planted in the northeastern zones with single harvesting, achieving a total attainable economic benefit of 24.2 billion US$. These findings emphasize that replacing corn with perennial bioenergy crops on sloping farmland with high risk of nutrient loss and low productivity can provide a win‐win situation for environmental protection and agricultural sustainability.