An overview of soil classification

Soil Taxonomy is composed of six levels: order, suborder, great group, subgroup, family, and series (figure 5–4). The system has been designed to classify any soil in the world and can be complex. The taxonomic name of a soil contains a great deal of information about the nature and properties of that specific soil. For the purposes of this book we will focus only on the highest (order) and lowest (series) levels.
Soil orders are the most general level of classification in soil taxonomy. Orders are similar to kingdoms in the Linnaeus system of classifying organisms. Each order is based on one important diagnostic feature such as permafrost for Gelisols or shrink–swell clays for Vertisols. The taxonomy follows a strict dichotomous sequence, so that once a soil is placed in an order it cannot be moved to another order. The key diagnostic feature for a given order is based on its significant effect on the land use or management of all soils in that order. The orders also represent different weathering intensities or degrees of formation.