1. Dep. of Agronomy; 116 ASI Building, Pennsylvania State Univ. University Park PA 16802 USA
2. Dep. of Natural Resources and Environmental Sciences; Univ. of Illinois; 1102 S. Goodwin Ave. Urbana IL 61801 USA
3. Dep. of Crop Sciences; Univ. of Illinois; 1102 S. Goodwin Ave. Urbana IL 61801 USA
4. USDA; 1102 S. Goodwin Ave. Urbana IL USA