Agricultural best management practices (BMPs) contribute to reducing non-point source pollution to the Great Lakes. The field-scale cost-effectiveness of nutrient management in the 1,430 ha Gully Creek watershed, south-eastern Ontario was assessed, and the effectiveness of BMP targeting schemes at improving outlet water quality was compared. Baseline scenario results showed outlet loading of 22,018 kg/yr for nitrogen and 5,077 kg/yr for phosphorus. Full adoption reduced nitrogen loading to 21,904 kg/yr and phosphorus loading to 5,060 kg/yr while average net returns increased by $13,370 per year. On fields which most improved water quality, average nitrogen and phosphorus abatement cost-effectiveness was -$35 per kg and -$1,271 per kg respectively. Targeting schemes based on farm size, excess nutrient application, edge-of-field abatement, and outlet abatement were compared. The most effective scheme was targeting by outlet abatement, which only required approximately 25% of cropland to achieve 75% of maximum potential nutrient abatement.