K, Kf, Kr, and I factors are for the surface layer. Use K in the USLE equation, and do NOT count rock fragments as part of the mulch cover. Kr is Kf adjusted for seasonal variation in weather and soil surface properties. I indicates susceptibility to wind erosion. I ranges from 0 to 310.
Higher numbers mean higher susceptibility to erosion.
Used to estimate runoff from precipitation. Groups are A, B, C, and D. Group A has the least runoff and D the most. See the hydric soils list for more information. See HEL list for more information.