1. USDA-ARS; Agroecosystem Management Research Unit; Rm. 118 Keim Hall Univ. of Nebraska-East Campus Lincoln NE 68583
2. Dep. of Soil, Water, and Climate; Univ. of Minnesota; 439 Borlaug Hall 1991 Upper Buford Cir. St. Paul MN 55108
3. Dep. of Agronomy and Plant Genetics; Univ. of Minnesota; 411 Borlaug Hall 1991 Upper Buford Cir. St. Paul MN 55108