The Twelve Soil Orders

January 26, 2012 Print Friendly and PDF

Soils are the foundation of rangeland and impact the plant community and dependant animal and human communities.  The need to better understand soils, how they are formed and their physical properties led the United States Department of Agriculture's Soil Survey staff to publish Soil Taxonomy in 1975. This system for classifying soils has undergone numerous changes since that time, and the second edition was published in 1999. Soil Taxonomy remains one of the most widely used soil classification systems in the world. 

The links below take you to the 12 Soil Orders, a site developed by the University of Idaho that provides detailed information on the distribution, properties, ecological significance and use of the following 12 soil orders:

Soil Orders
  1. Gelisols - Learn more about Gelisols,  the unique soils found in the coldest regions of the earth.
  2. Histosols -Learn more about these soils that contain so much organic matter they can be burned for fuel!
  3. Spodosols - Learn more about these acidic soils found in moist climates that often support large, dense forests.
  4. Andisols - Learn more about these soils born from the ash of volcanoes.
  5. Oxisols - Discover more about the red soils found in tropical regions of the world.
  6. Vertisols - Did you know that soils can move? Learn about the soil that shrinks and swells in response to moisture.
  7. Aridisols - As their name suggests these soils are found in arid regions and are important supporters of rangelands.
  8. Ultisols - Learn more about the clay soils that occupy much of the southeastern United States and other regions of the world.
  9. Mollisols - Often referred to as the "grassland soil", mollisols are among the most important and productive agriculture soils of the world.
  10. Alfisols - Learn more about these highly productive soils found in termperate and humid regions of the world.
  11. Inceptisols - Learn more about these thin soils found on steep slopes and mountain ranges.
  12. Entisols - The most extensive of the soil orders, entisols are relatively young soils found in steep, rocky settings.

Soil Orders Poster from USDA NRCS


Connect with us

  • Twitter
  • Facebook
  • YouTube
  • Pinterest
  • Google+


This is where you can find research-based information from America's land-grant universities enabled by




This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.