Consideration of Suffix Symbol on Soil Taxonomy and World Reference Base for Soil Resources Classification

There is a difference between ST and WRB in distinguishing the master horizon. When a pedologists investigate a soil profile, it is difficult to determine which classification method to choose including the master horizon, add a prefix, suffix, etc. to the horizon name. The suffix symbol for groundwater level uses ‘g’ for ST and ‘l’ or ‘r’ for WRB. The suffix symbol ‘r’ represents a strong reduction state, and ‘l’ is used in a state where oxidation is much progressed. However, in the real agricultural field, the groundwater level is lowered so that the oxidized part of the profile is classified based on < 2%, 2 - 20%, > 20%. In addition, there are soils with a mottle quantity of 20 to 49%. ST classifies this as one like ‘g’, and WRB distinguishes it. However, since only the presence of a mottle is determined, a refinement is required. The proposals of mottle amounts 'r' in ST & WRB. Present Proposals Mottle quantity ST WRB Mottle quantity ST WRB few (< 2%) g l few (< 2%) g l common (2 - 20%) r common (2 - 20%) r many (≥ 20%) many (≥ 20%, < 50%)