1. Assistant Professor, Dept. of Biological Systems Engineering, Univ. of Nebraska-Lincoln, 234 L.W. Chase Hall, Lincoln, NE 68583-0726 (corresponding author).
2. Assistant Professor, Dept. of Biological Systems Eng., Univ. of Nebraska-Lincoln, West Central Research and Extension Center, 461 W. University Drive, North Platte, NE 69101.
3. Professor, Dept. of Biological Systems Engineering, Univ. of Nebraska-Lincoln, 230 L.W. Chase Hall, Lincoln, NE 68583-0726.
4. Research Assistant Professor, Dept. of Biological Systems Engineering, Univ. of Nebraska-Lincoln, 253 L.W. Chase Hall, Lincoln, NE 68583-0726.
5. Supervisory Agricultural Engineer and Research Leader, USDA-ARS Conservation and Production Research Laboratory, P.O. Drawer 10, Bushland, TX 79012-0010.