1. Univ. of Arkansas Dep. of Crop, Soil, and Environ. Sci. 1366 W. Altheimer Drive, Fayetteville AR 72704
2. USDA‐ARS, Univ. of Florida, Agron. Physiol. and Genet. Lab. IFAS Bldg. no. 350, 2005 SW 23rd St., P.O. Box 110965 Gainesville FL 32611‐0965
3. Agric. Stat. Lab., Agriculture Annex 101, Univ. of Arkansas Fayetteville AR 72704