Bulletin #1087, Soil pH (PDF) By Steven B. Johnson, Ph.D., Extension Crops Specialist, and John Jemison, Extension Professor, Soil and Water Quality, University of Maine Cooperative Extension For information about UMaine Extension programs and resources, visit extension.umaine.edu.Find more of our publications and books at extension.umaine.edu/publications/. Soil pH is the measurement of “potential of hydrogen.” It