1. USDA-ARS; Crop Production Systems Research Unit; PO Box 350 Stoneville MS 38776
2. Agricultural and Environ. Serv. Lab.; Univ. of Georgia; 2400 College Station Road Athens GA 30602-9105
3. Dep. of Crop and Soil Sciences; Univ. of Georgia Miller Plant Sciences; Building 120 Carlton Street Athens GA 30602
4. USDA-ARS Central Great Plains Res. Station; 40335 County Road GG Akron CO 80720
5. Instituto Nacional de Tecnología Agropecuaria; Ruta Nacional N° 5 Km. 580, (6326) Anguil La Pampa Argentina