Soil loss tolerance is the maximum average annual soil removal by erosion that will allow continuous cropping and maintain soil productivity (T). It is occasionally defined as the maximum amount of soil erosion offset by the maximum amount of soil development while maintaining an equilibrium between soil losses and gains. T is usually expressed in terms of tons per acre or tons per hectare. Because T values are difficult to quantify, they are usually inferred by human judgment rather than scientific analysis. In determining T values, the depth of the soil to consolidated material or depth to an unfavorable subsoil is considered. T values are an expression of concern for plant growth but may not adequately reflect environmental concerns.