1. USDA-ARS, Soil and Water Management Research Unit; 439 Borlaug Hall, 1991 Upper Buford Cir. St. Paul MN 55108
2. International Center for Tropical Agriculture (CIAT); Av. La Molina 1581 La Molina Lima Perú
3. USDA-ARS, Grassland, Soil and Water Research Lab.; 808 E. Blackland Rd. Temple TX 76502
4. USDA-ARS, North Central Agricultural Research Lab.; 2923 Medary Ave. Brookings SD 57006
5. Dep. of Plant and Soil Sciences; Oklahoma State Univ.; 368 Agricultural Hall Stillwater OK 74078-6028
6. North Central Soil Conservation Research Lab.; 803 Iowa Ave. Morris MN 56267