The Twelve Soil Orders
Soil Taxonomy is a soil classification system developed by the United States Department of Agriculture’s soil survey staff. This system is based on measurable and observable soil properties and was designed to facilitate detailed soil survey. Although it is not the only system for classifying soils, Soil Taxonomy is widely used worldwide and many of its features have been adopted into other systems.
At the highest level of classification, Soil Taxonomy places soils into one of 12 categories known as “orders.” Each of these orders represents a grouping of soils with distinct characteristics and ecological significance. To illustrate this, we have put together a collection of images and information to highlight the distribution, properties and land use for each of the 12 soil orders.
A map of the United States showing dominant soil orders.
Sources of all images used on this website are noted. Additional information about the soils is derived from the following sources unless otherwise noted.
- Soil Survey Staff. 1999. Soil Taxonomy, 2nd ed. USDA-NRCS, Washington, DC.
- Soil Survey Staff. 2014. Keys to Soil Taxonomy. 12th ed. USDA-NRCS, Washington, DC.
- USDA. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. USDA-NRCS, Washington, DC.
- USDA-NRCS. 2018. Official soil series descriptions. Accessed at: https://soilseries.sc.egov.usda.gov
The second edition of Soil Taxonomy, A Basic System of Soil Classification for Making and Interpreting Soil Surveys is available for download or order a printed copy through the Natural Resources Conservation Service, United States Department of Agriculture.