US Soil Taxonomy (ST)
Developed by United States Department of Agriculture and the National Cooperative Soil Survey.
Soil taxonomy provided by United States Department of Agriculture/Natural Resources Conservation Centre provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.
For a copy of the main Soil Taxonomy document, go to the USDA-NRCS Soil Taxonomy webpage. The latest version is the 2nd edition published in 1999.
There also is a Keys to Soil Taxonomy document providing the taxonomic keys necessary for the classification of soils in a form that can be used easily in the field. It also acquaints users of soil taxonomy with recent changes in the classification system, incorporating all changes approved since 1999.
Horizon Definitions are provided in Chapter 3, and the Identification Key starts in Chapter 4 and then branches to the appropriate chapter for further distinction within each soil order.