Cost-effectiveness is an important consideration in evaluating choices for meeting environmental quality objectives. Estimated crop yield response functions and the associated groundwater-nitrate pollution production functions were used to evaluate the optimal N fertilization and on-farm abatement costs for alternative cropping systems, with management choices at both the intensive and extensive margins. The cost-effective corn production system, which meets the Health Canada standard for nitrates with the highest returns ($278 ha-1) and lowest on-farm abatement cost ($248 ha-1), was a four-year corn-corn-soybean-wheat rotation under conventional tillage. At contaminant limits above the Health Canada standard, the cost-effective wheat cropping system shifted from a soybean-wheat rotation under no-tillage to a corn-soybean-wheat rotation under no-tillage.