1. Eastern Nebraska Research, Extension and Education Center Univ. of Nebraska–Lincoln 1701 CR G Ithaca NE 68033 USA
2. Dep. of Agronomy and Horticulture Univ. of Nebraska–Lincoln 202 Keim Hall Lincoln NE 68583 USA
3. Dep. of Agricultural and Biological Engineering Penn State Univ. 105A Agricultural Engineering Building, Shortlidge Rd. University PA 16082 USA
4. Biological Systems Engineering Dep. Univ. of Nebraska–Lincoln 223 L.W. Chase Hall Lincoln NE 68583 USA