1. Dep. of Soil, Water and Climate; Univ. of Minnesota; St. Paul MN 55108
2. USDA-ARS Soil and Water Management Research Unit; 1991 Upper Buford Cir., Rm. 439 St. Paul MN 55108
3. Instituto de Recursos Naturales y Agrobiologia de Sevilla, CSIC; P.O. Box 1052 41080 Seville Spain
4. Bayer Corporation; 17745 South Metcalf Stilwell KS 66085