http://www.ctahr.hawaii.edu/mauisoil/c_acidity.aspx http://www.ctahr.hawaii.edu/deenikj/Downloads/Training/SoilFertility_Maui.pdf Like the Mt. Shasta, CA., area, Maui is a volcanic area with a relatively high amount of naturally occurring aluminum in the soil. Unlike Mt. Shasta, many areas in Maui have acid soil, related to the precipitation of 60-120 inches per year. This causes the aluminum to become chemically active, and toxic to some plants. This could easily explain the problems shown in WITWATS. A picture on page 21 from the second reference shows areas of aluminum toxicity in Maui.