Stanley W. Buol, Ph.D., is William Neal Reynolds Distinguished Professor of Soil Science and Alumni Distinguished Graduate Professor at North Carolina State University, Raleigh. Randal J. Southard, Ph.D., is Professor of Soil Genesis and Morphology and Associate Dean of the College of Agricultural and Environmental Sciences at the University of California, Davis. Robert C. Graham, Ph.D., is Professor of Soil Mineralogy and Pedology at the University of California, Riverside. Paul A. McDaniel, Ph.D., is Associate Professor of Soil Genesis and Morphology at the University of Idaho, Moscow.