1. USDA‐ARS Southern Regional Research Center 1100 Robert E Lee Blvd. New Orleans LA 70124
2. Pontotoc Ridge‐Flatwoods Branch Experiment Station Mississippi State Univ. Pontotoc MS 38863
3. Dep. of Plant and Soil Sciences Oklahoma State University Stillwater OK 74078
4. USDA‐ARS National Soil Dynamics Laboratory Auburn AL 36832
5. USDA‐ARS Crop Science Research Laboratory Mississippi State MS 39762