|Williams, John - USDA-ARS PENDLETON, OR|
Submitted to: Seasonally Frozen Soils Symposium
Publication Type: Proceedings
Publication Acceptance Date: March 1, 1997
Publication Date: N/A
Interpretive Summary: Erosion on cropland on non-irrigated cropland of the Pacific Northwest is caused in large part by low intensity rains and snowmelt when the soil is thawing. The soil is weakened by the thaw, and runoff removes the easily detached soil particles. An eight-year study at the Palouse Conservation Field Station near Pullman, Washington provided data to determine the effect of surface cover on soil erosion under these conditions. The data indicated a given amount of surface cover to have a greater effect on soil erosion under these conditions as compared to high-intensity rainstorms. The results improve the performance of the Revised Universal Soil Loss Equation in the Pacific Northwest, the primary erosion prediction tool of the NRCS used for farm planning and to meet requirements of the Food Security Act. The improvement will help ensure least-cost measures are used to provide the required level of erosion.
Technical Abstract: Erosion on cropland in the Northwestern Wheat and Range Region (NWRR) of the Pacific Northwest is caused in large part by runoff from low intensity rains and snowmelt when the soil is thawing. Under these conditions, crop management elements such as crop residue have different effects on runoff and erosion than they do under nonfrozen conditions with high-intensity rainstorms. The primary differences are that under NWRR conditions, the erosion is caused by flowing water rather than raindrop impact and that the soil is weakened because of dispersion and high moisture content. An eight-year study at the Palouse Conservation Field Station near Pullman, Washington, provided data to isolate the effect of surface cover on erosion and to fit a relationship for use in the Revised Universal Soil Loss Equation. The relationship indicates a greater relative effect of surface cover when compared to high-intensity summer rainstorm conditions.