1. USDA-ARS; National Soil Tilth Lab.; 2150 Pammel Dr. Ames IA 50011
2. USDA-NRCS; Soil Quality Inst.; 2150 Pammel Dr. Ames IA 50011
3. USDA-ARS, Soil and Water Research Unit; Univ. of Nebraska; Lincoln NE 68583
4. USDA-Forest Service; Washington DC 20090-6090
5. Dep. of Soil Science, 1525 Observatory Dr.; Univ. of Wisconsin; Madison WI 53706
6. USDA-ARS, High Plains Grasslands Research Station; 8408 Hildreth Rd. Cheyenne WY 82009