Farmers and taxpayers would benefit from more cost-effective agricultural nutrient pollution control measures. The objectives of our study are (1) to assess compliance costs and reductions in phosphorus loadings from implementation of nutrient management and riparian buffers; and (2) to estimate how the spatial scenario, which is the method of representing farms within the watershed, affects estimated compliance costs and reductions in phosphorus deliveries. Estimated compliance costs are quite sensitive to the spatial scenario. Buffers are more cost-effective than nutrient management under one of the two spatial scenarios, whereas nutrient management is more cost-effective under the other scenario. Shifts to more erosive crops reduce the effectiveness of both pollution control measures.