1. Department of Plant Sciences, Loftsgard Hall, North Dakota State University, Fargo, North Dakota 58105
2. Soil and Water Management Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Room 439, 1991 Upper Buford Circle, St. Paul, Minnesota 55108
3. Department of Agronomy and Plant Genetics, 411 Borlaug Hall, University of Minnesota, St. Paul, Minnesota 55108