1. Dep. Soil ScienceUniv. of Wisconsin‐MadisonMadisonWI53706‐1299
2. Hydrology Lab.USDA‐ARS, BARC‐WBeltsvilleMD20705‐2350
3. Dep. AgronomyPurdue Univ.West LafayetteIN47907
4. Dep. Biological and Environmental EngineeringCornell Univ.IthacaNY14850
5. National Soil Tilth Lab.USDA‐ARSAmesIA50011