Soil erosion policy aiming to remove highly erodible land from production to reduce soil erosion may be dealing with some of the most productive and valuable U.S. cropland. If so, greater incentives for farmers to retire that land may be needed. The land capability classification system and USDA's prime farmland definition, used to measure the suitability of land for agricultural uses, do not provide enough information for decisions on whether highly erodible soils are less or more productive than less erodible soils. As a result, some highly erodible lands that are also highly productive may have higher opportunity costs than commonly thought and thus may need greater incentives for retirement. Opportunity costs measure the earning power of an input, soil in this case, in its best alternative use.