DIAGNOSTIC SOIL HORIZONS IN SOIL TAXONOMY

This paper discusses the major kinds of soil horizons, their use in Soil Taxonomy, and their significance in engineering soil behavior. The characteristics of the soil in any place are a result of the combined influence of climate and living organisms on a specific kind of parent soil material, conditioned by relief, over a period of time. The combined effect of these factors is reflected in most soils as soil horizons of unique kinds. The presence or absence of kinds of soil horizons is an important criterion in the definition of classes in Soil Taxonomy. Each key soil horizon has a unique morphology that reflects its genesis and composition and a unique behavior due to its properties. Some soil horizons have accumulated clays, organic matter, or iron and other minerals. Other soil horizons have lost such materials. In the classification and mapping of soils the pedologist studies the properties of each soil horizon in situ and, on the basis of this study, selects sites for obtaining samples of soils for characterization in the laboratory. /Author/