Alternate strips of grass or legumes between Buffer Strip Cropping: other crops (normally in rotation). Often plant buffer strips on steep unfarmable portions of fields. MAJOR WEAKNESSES OF THE USLE Empirically based equation which uses variables that are to a • degree indices of factors that affect soil erosion. Erosion processes are not explicitly represented as physical • processes in the USLE. Poor representation of erosion, infiltration, slope, slope length, and especially contouring. USLE is a regression equation developed from a limited data • base. When the equation is applied to new situations, new experimental data are usually required. Most of the USLE data are from cropland. Extension of the • USLE to range land, forest land, and construction sites without an extensive data base has been highly controversial. Not designed for individual storm analysis. Does not predict • particle size distributions required for water quality work. Problems with contour tillage accurately representing field • slopes. Problems with individual USLE factors: EI - Does not accurately reflect rainfall characteristics in all • regions. K - The more we study it, the less we seem to know (Romkens). • S - Too large on steep slopes. The relationship is more linear • on steep slopes. C - Canopy and soil roughness effects are not represented well. • P - For contouring should vary with ridge height and EI of 10 • year storm.
Buffer Strip Cropping: Alternate strips of grass or legumes between other crops (normally in rotation). Often plant buffer strips on steep unfarmable portions of fields. MAJOR WEAKNESSES OF THE USLE • Empirically based equation which uses variables that are to a degree indices of factors that affect soil erosion. • Erosion processes are not explicitly represented as physical processes in the USLE. Poor representation of erosion, infiltration, slope, slope length, and especially contouring. • USLE is a regression equation developed from a limited data base. When the equation is applied to new situations, new experimental data are usually required. • Most of the USLE data are from cropland. Extension of the USLE to range land, forest land, and construction sites without an extensive data base has been highly controversial. • Not designed for individual storm analysis. Does not predict particle size distributions required for water quality work. • Problems with contour tillage accurately representing field slopes. Problems with individual USLE factors: • EI - Does not accurately reflect rainfall characteristics in all regions. • K - The more we study it, the less we seem to know (Romkens). • S - Too large on steep slopes. The relationship is more linear on steep slopes. • C - Canopy and soil roughness effects are not represented well. • P - For contouring should vary with ridge height and EI of 10 year storm.
Erosion%20and%20Sedimentation.docx