1. Department of Plants, Soils, and Biometeorology, Utah State University, Logan, Utah 84322-4820, Department of Agronomy, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803-2110, Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware 19717-1303, USDA-ARS, U.S. Salinity Laboratory, 450 Big Springs Road, Riverside, California 92507, and Battelle, Pacific Northwest Laboratory, Richland, Washington 99352