1. South Dakota State University Box 2207A Brookings SD 57007 USA
2. Universtiy of Minnesota 1991 Upper Buford Circle St. Paul MN 55108 USA
3. Purdue University Lilly 3‐365 West Lafayette IN 47907 USA
4. Agronomist (retired) Clive IA 50325 USA
5. University of Nebraska Keim 367 Lincoln NE 68583 USA
6. North Dakota State Univ. PO Box 6050 Fargo ND 58108 USA
7. USDA‐ARS Cropping Systems and Water Quality Research Unit 243 Agric. Eng. Bldg. Columbia MO 65211 USA
8. University of Wisconsin‐Madison 1525 Observatory Dr. Madison WI 53706 USA
9. University of Illinois W‐301 Turner Hall, 1102 S. Goodwin Urbana IL 61801 USA
10. Iowa State University 3208 Agronomy Hall Ames IA 50011 USA
11. Fortigen 6807 Ridge Rd Lincoln NE 68512 USA