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Organosols [OR]


This class caters for most soils dominated by organic materials. Although they are found from the wet tropics to the alpine regions, areas are mostly small except in south west Tasmania. There have been few previous attempts to subdivide these soils and data are limited in Australia.

Distribution of Organosols in Australia.
Soil Profile (View type example photo of Hemic Organosol).


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.


The above definition is similar to definitions of organic soils in Soil Taxonomy (1975) and in Canada (Canada Soil Survey Committee 1978).



These suborders are essentially the same as in Soil Taxonomy. The terms fibric, hemic and sapric correspond to fibrous, mesic (semifibrous) and humic as used in Canada and England and Wales. In some north Queensland seasonal swamps, thick peats can have 0.3-0.4 m of sapric over hemic and/or fibric peat. When more data are available it may be necessary to modify the suborder definitions to cater for soils where the type of peat changes with depth.

Great Groups

It is likely that not all of the great groups below will be applicable to each suborder. It is also likely that other great groups will be required as knowledge increases.


The following subgroups may not be relevant to all great groups of each suborder, and future investigations may reveal additional subgroups.

Possible Family Criteria

Nature of uppermost organic materials

The term granular [P] is applied if there is a surface layer at least 0.2 m thick which has a distinct granular or subangular blocky structure. This condition occurs in peat soils that have been either drained or drained and cultivated, and is also known as earthy or ripened peat. In Australia it is known to occur with sapric peats, but it is uncertain if it occurs with hemic or fibric peats.

Cumulative thickness of organic materials1

Very thin [T] : < 0.25 m
Thin [U] : 0.25 - < 0.5 m
Moderate [V] : 0.5 - < 1.0 m
Thick [W] : 1.0 - < 1.5 m
Very thick [X] : 1.5 - 5 m
Giant [Y] : > 5 m

1 These codes are the same as those used for soil depth, which have the same class limits, in the other orders.

[ AN ] [ OR ] [ PO ] [ VE ] [ HY ] [ KU ] [ SO ] [ CH ] [ CA ] [ FE ] [ DE ] [ KA ] [ RU ] [ TE ]