1. South Dakota State Univ. Dep. of Animal and Range Sciences Box 2170 Brookings SD 57007‐0392
2. Univ. of Nebraska‐Lincoln Agronomy and Horticulture Dep. 279 Plant Sci., P.O. Box 830915 Lincoln NE 68583
3. Univ. of Nebraska‐Lincolon Agronomy and Horticulture Dep., West Central Research and Extension Center 461 West University Drive North Platte NE 69101