Runoff from low intensity rains and snowmelt when the soil is thawing is a major if not primary cause of erosion on cropland in the Northwestern Wheat and Range Region (NWRR) of the Pacific Northwest. Under these conditions, crop management elements such as crop residue have different effects on runoff and erosion than under non-frozen conditions with high-intensity rain storms; the eroding force is flowing water and the soil is weakened because of high moisture content. A thirteen-year runoff plot study at the Palouse Conservation Field Station near Pullman, WA and a similar study at the Columbia Plateau Conservation Research Center near Pendleton, OR provided data to isolate the effect of crop residue on runoff and erosion and to fit a relationship for use in RUSLE. This paper will provide procedures, analysis and results of this study.

D.K. McCool
Agricultural Engineer
USDA-ARS
Biological Systems Engineering Department
Washington State University
Pullman, WA  99164-6120
Phone:  509-335-1347
FAX:  509-335-7786
E-mail:  dkmccool@wsu.edu