For example, if spring wheat is grown on one quarter of the total CRAM region's cropland, then the C value for spring wheat is multiplied by 0.25 to produce a weighted spring wheat value. The weighted values for all crops in the region are summed to obtain a weighted C value for the region. Tolerable losses are defined as less than 6 tonnes per hectare per year. Low rates range from 6.0 to 10.9 tonnes per hectare per year and moderate rates range from 11.0 to 21.9 tonnes per hectare per year. High and severe classes comprise rates of 22.0 to 32.9 and greater than 32.9 tonnes per hectare per year respectively.
Soil formation is generally in equilibrium with soil loss.
The other classes of soil erosion represent conditions where the implementation of soil and water conservation practices are required for sustained production of agricultural crops. The conceptual procedure for estimating the risk of wind erosion involves the calculation of inherent risk on bare unprotected soil, which is then modified by an erosion reduction factor. This factor accounts for the effectiveness of the cover or management practices in reducing the inherent risk. Pertinent soil and landscape attributes are recorded for each SLC polygon. Climate and land use parameters are linked to the SLC polygons to provide an integrated land resource digital database to facilitate analysis.