1. Dep. of Crop Sciences; Univ. of Illinois; 1102 S. Goodwin Ave. Urbana IL 61801
2. 1575 Linden Dr., Dep. of Agronomy; Univ. of Wisconsin-Madison; Madison WI 53706
3. This research was partially supported by funding through USDA Cooperative State Research Education and Extension Service (CSREES) Hatch Project WIS04802