1. a Department of Agronomy , University of Georgia , Georgia Experiment Station, Griffin , GA , 30223
2. b Agronomy Department , University of Maryland , College Park , MD , 20742
3. c Department of Crop, Soil, and Environmental Sciences , Virginia Tech , Blacksburg , VA , 24061
4. d Agricultural Services Lab. , University of Georgia , 2400 College Station Road, Athens , GA , 30605
5. e Agricultural Service Laboratory , Clemson University , Clemson , SC , 29634
6. f Department of Plant and Soil Sciences , University of Delaware , Newark , DE , 19711
7. g Agronomic Division, North Carolina Department of Agriculture , Raleigh , NC , 27610