Bryan G. Hopkins is a Professor at Brigham Young University and a Certified Professional Soil Scientist. He is the Coordinator for the Soil Science Society of America--North American Proficiency Testing Program. He has degrees from Ricks College, Brigham Young University, and Kansas State University in Agronomy & Horticulture with specialties in soil biophysical chemistry and plant nutrition. He has published dozens of peer reviewed manuscripts and book chapters and hundreds of research reports and given countless presentations. Dr Asher Bar-Tal is a Senior Researcher at the Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization (ARO, the Volcani Center) of Israel. In 1987 he earned Ph.D. from The Hebrew University of Jerusalem. From 2011 to 2013 he served as the Chairman of the Department of Soil Chemistry, Plant Nutrition and Microbiology, Institute of Soil, Water and Environmental Sciences, The Volcani Center, ARO. Dr Bar-Tal currently serves as the president of the Israeli Society of Soil Science. His research interests focus on soil chemistry, plant nutrition and fertilization of crops.