We use parametric and nonparametric methods to estimate correlations between average control cost and three field-level characteristics—field size and delivered phosphorous per field and per acre—as proxies for economies of scale in controlling nonpoint pollution. We combine load and delivery-ratio estimates for more than 12,000 fields in the Bear River Basin, Utah, with estimates of control costs and effectiveness of management practices from the literature. Results suggest a negative relationship between control cost and delivered phosphorous per field and per acre. Ranking fields by phosphorous load therefore prioritizes management-practice subsidies by economies of scale.