Frederick R. Troeh, PhD, is Professor Emeritus, Agronomy, Iowa State University, Ames, where he taught for over 30 years. Dr. Troeh has numerous years of experience in the field of soil science with an emphasis on soil conservation and has worked abroad in Uruguay, Argentina, and Morocco. The late Roy L. Donahue, PhD, was Professor in the field of soil ... Read morescience at Michigan State University, East Lansing, as well as educator in India and Africa. He assembled much of the background material for this dictionaryFrederick R. Troeh, PhD, is Professor Emeritus, Agronomy, Iowa State University. He has taught for over 32 years at Iowa State University and has numerous years of experience in the field of soil science. Roy L. Donahue, PhD, was a great teacher and instigator of textbooks and other writing projects (he sadly died in 1999). He assembled most of the background material for this dictionary over a period of approximately ten years. Show Less