Soil Classification
Soils are classified into twelve orders that are distributed around the world and broken down into suborder, great group, subgroup, family, and series1. The soils are differentiated based on climate, horizons, and presence of organic material1.

The 12 soil orders are*:
1. Gelisols- has permafrost within 2 meters of the surface
2. Histosols- contains significant organic material
3. Spodosols- subsurface of metal-humus complexes, characteristic of acid forest soils
4. Andisols- formed in volcanic ash
5. Oxisols- heavily weathered soils, characteristic of the tropics and subtropics
6. Vertisols- clayey with high capacity to shrink and swell
7. Aridisols- contains Calcium Carbonate, characteristic of arid environments
8. Ultisols- leached soils with a subsurface zone of clay accumulation <35% base saturation
9. Mollisols- grassland soils with high base status
10. Alfisols- moderately leached soils with a subsurface zone of clay accumulation and >35% base saturation
11. Inceptisols- soils with weakly developed subsurface horizons
12. Entisols- soils with little of no morphological development

Soils are also rated on their agriculture potential on a scale from I-VIII, where Class I is best suited for agriculture use with the least limitation to use2.

(*Soil orders composed by Lowes & Chambers, 2008 based on USDA, NRCS data1)

Soil Classification Translation Needed

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1. McDaniel, P. (2008) The twelve soil orders. Available at (accessed June 2008).
2. Enright, C., Hulse, D., & Richey, D. (no date) Soils: Willamette River Basin Atlas, 2nd Edition. Available at (accessed July 2009).

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