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The Classification

Key to Soil Orders

The material below is arranged to give the simplest way of identifying a particular soil in terms of the Orders, and is not a complete definition of each Order. Work successively through the key until an apparent identification is made, then check the full definition of the Order by clicking on the highlighted name. Words or phrases in italics are defined in the Glossary.

  1. Soils resulting from human activities.
    ANTHROPOSOLS
  2. Soils that are not regularly inundated by saline tidal waters and either:
    1. Have more than 0.4 m of organic materials within the upper 0.8 m. The required thickness may either extend down from the surface or be taken cumulatively within the upper 0.8 m; or
    2. Have organic materials extending from the surface to a minimum depth of 0.1 m; these either directly overlie rock or other hard layers, partially weathered or decomposed rock or saprolite, or overlie fragmental material such as gravel, cobbles or stones in which the interstices are filled or partially filled with organic material. In some soils there may be layers of humose and/or melacic horizon material underlying the organic materials and overlying the substrate.
    ORGANOSOLS
  3. Other soils that have a Bs, Bhs or Bh horizon (see Podosol diagnostic horizons).

    These horizons may occur either singly or in combination. PODOSOLS

  4. Other soils that:
    1. Have a clay field texture or 35% or more clay throughout the solum except for thin, surface crusty horizons 0.03 m or less thick, and
    2. Unless too moist, have open cracks at some time in most years that are at least 5 mm wide and extend upward to the surface or to the base of any plough layer, self-mulching horizon, or thin, surface crusty horizon, and
    3. At some depth in the solum, have slickensides and/or lenticular peds.
    VERTOSOLS
  5. Other soils that are saturated in the major part1 of the solum for at least 2-3 months in most years (ie. includes tidal waters).
    6. HYDROSOLS
  6. Other soils with a clear or abrupt textural B horizon and in which the major part1 of the upper 0.2 m of the B2 horizon (or the major part of the entire B2 horizon if it is less than 0.2 m thick) is strongly acid.
    7. KUROSOLS
  7. Other soils with a clear or abrupt textural B horizon and in which the major part1 of the upper 0.2 m of the B2 horizon (or the major part of the entire B2 horizon if it is less than 0.2 m thick) is sodic and is not strongly subplastic.
    8. SODOSOLS
  8. Other soils with a clear or abrupt textural B horizon and in which the major part1 of the upper 0.2 m of the B2 horizon (or the major part of the entire B2 horizon if it is less than 0.2 m thick) is not strongly acid.
    9. CHROMOSOLS
  9. Other soils that:

    Are either calcareous throughout the solum - or calcareous at least directly below the A1 or Ap horizon, or within a depth of 0.2 m (whichever is shallower). Carbonate accumulations must be judged to be pedogenic, ie. are a result of soil forming processes in situ (either current or relict) in contrast to fragments of calcareous rock such as limestone or shell fragments. See also calcrete. CALCAROSOLS

  10. Other soils with B2 horizons in which the major part1 has a free iron oxide content greater than 5% Fe in the fine earth fraction (<2 mm). Soils with a B2 horizon in which at least 0.3m has vertic properties are excluded (see also Comment and footnote in Ferrosols).
    11. FERROSOLS
  11. Other soils with B2 horizons that have structure more developed than weak2 throughout the major part1 of the horizon.
    12. DERMOSOLS
  12. Other soils that:
    1. Have well-developed B2 horizons in which the major part1 is massive or has only a weak grade of structure, (compare with tenic B horizon and cemented pans), and
    2. Have a maximum clay content in some part of the B2 horizon which exceeds 15% (ie. heavy sandy loam, SL+).
    KANDOSOLS
  13. Other soils with negligible (rudimentary) pedological organisation apart from the minimal development of an A1 horizon or the presence of less than 10% of B horizon material (including pedogenic carbonate) in fissures in the parent rock or saprolite. The soils are apedal or only weakly structured in the A1 horizon and show no pedological colour change apart from darkening of an A1 horizon. There is little or no texture or colour change with depth unless stratified or buried soils are present. Cemented pans may be present as a substrate material.
    14. RUDOSOLS
  14. Other soils.
    15. TENOSOLS

1 The 'major part' means the requirement must be met over more than half the specified thickness. Analyses or estimates should be used from horizons or subhorizons that subdivide the profile, or if the subhorizons are not recognised, then from subsamples of the relevant horizons.

2 It is common experience that pedologists are inclined to use the phrase 'weak to moderate' when they are in doubt as to the grade of the structure. If such a designation is used it will result in the soil being classed as a Dermosol.