1. Dep. of Crop, Soil and Environmental Sciences, 115 Plant Sciences Building; Univ. of Arkansas; Fayetteville AR 72701
2. USDA-ARS; Pasture Systems and Watershed Management Research Unit; Building 3702, Curtin Road University Park PA 16802-3702
3. Centre for Sustainable Water Management, Lancaster Environment Centre; Lancaster Univ.; Lancaster LA1 4YQ UK