1. USDA, Agriculture Research Service, National Soil Erosion Research Lab, 275 South Russell St., West Lafayette, Indiana 47907, United States
2. Washington State University, PO Box 646420, Pullman, Washington 99164-6420, United States
3. International Plant Nutrition Institute, 3500 Parkway Lane, Suite 550, Peachtree Corners, Georgia 30092-2844, United States