Alfred R. Conklin, Jr., PHD, is a Professor in the Agriculture and Chemistry departments at Wilmington College in Wilmington, Ohio. He has been a Fulbright Professor and Lecturer at Leyte State University and Mariano Marcos State University in the Philippines and at the University of Zimbabwe. Dr. Conklin is the author of several books including Introduction to Soil Chemistry: Analysis and Instrumentation (Wiley). Thomas C. Stilwell, PHD, is a Professor in the Department of Agriculture at Wilmington College. He has also served as an agronomist in Asia, Africa, South America, and North America. Dr. Stilwell has worked with farmers to improve crop production in India, Bolivia, Mexico, Cameroon, Tunisia, Dominican Republic, and Ecuador.