University of Idaho College of Agricultural and Life Sciences Plant, Soil & Entomological Sciences Soil & Land Resources
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The Twelve Soil Orders
The 12 soil orders are listed below in the sequence in which they key out in Soil Taxonomy.
Click on the order name for more information and to view images of example soils and landscapes.
Gelisols - soils with permafrost within 2 m of the surface
Histosols - organic soils
Spodosols - acid forest soils with a subsurface accumulation of metal-humus complexes
Andisols - soils formed in volcanic ash
Oxisols - intensely weathered soils of tropical and subtropical environments
Vertisols - clayey soils with high shrink/swell capacity
Aridisols - CaCO3-containing soils of arid environments with subsurface horizon development
Ultisols - strongly leached soils with a subsurface zone of clay accumulation and <35% base saturation
Mollisols - grassland soils with high base status
Alfisols - moderately leached soils with a subsurface zone of clay accumulation and >35% base saturation
Inceptisols - soils with weakly developed subsurface horizons
Entisols - soils with little or no morphological development
     


If you have any comments, suggestions, or questions about the 12 Soil Orders web site,
please contact Dr. Paul McDaniellat the Soil and Land Resources Division,
University of Idaho, Moscow, ID 83844-2339.