1. USDA‐ARS, Cent. Great Plains Res. Stn. 40335 County Rd. GG Akron CO 80720
2. USDA‐ARS Conserv. and Prod. Res. Lab. P.O. Drawer 10 Bushland TX 79012
3. Dep. of Land Resour. and Environ. Sci. Montana State Univ. P.O. Box 173120 Bozeman MT 59717‐3120