Improved Criteria for Developing Soil Loss Tolerance Levels for Cropland

The present national objective of erosion control in the USA is to maintain the productivity of the soil resource and still allow for its maximum utilization. for agricultural land use, this objective is applied at the state and regional level as the soil loss tolerance (T) value; it is based on soil interpretation at the series level and ranges from 2 to 11 metric tons/ha/year (1 to 5 tons/acre/year). Used with the Universal Soil Loss Equation (USLE), it serves as a guide to farmers for selecting conservation practices suited to their soil and crop management conditions. The primary criterion currently used for establishing T values is topsoil thickness such that deeper soils can tolerate higher levels of annual erosion than shallower soils. This criterion is examined and several additional factors are considered: soil structure, existing erosion conditions, specific rooting requirements of crops, available erosion control technology, and non-point source pollution control objectives.