ERM Introduction to Soils and Soil Resources
The Canadian Soil Classification System


Principles of Scientific Soil Classification

In any science a system of classification is used to organize information about similar entities within a logical and easily remembered framework. Classification also allows us to discover relationships between these entities and to apply our knowledge towards the solution of practical problems. Classification schemes arrange objects in an orderly fashion by placing them into groups or "classes" or "taxa" according to their similarity to each other. Objects to be classified are arranged in such a way that they succeed or accompany each other. Application of this principle results in a hierarchical classification scheme. At the highest level, classes are based on broad generalizations which are further divided and defined through subsequent lower levels. Classification categories are thus most general at the highest level and most specific at the lowest level.


Canadian System of Soil Classification

Many different classification systems can be developed for the same group of objects. The Canadian System of Soil Classification is a scientific classification based on the natural relationships between soils and on characteristics that are important and precise. Five taxa are recognized in the hierarchical scheme used for the Canadian System of Soil Classification:

Orders differentiated on the basis of characteristics of the soils that reflect the nature of the total soil environment and the effects of the dominant soil forming processes
Great Groups differentiated on the basis of characteristics that reflect the differences in the strengths of the dominant processes or a major contribution of an additional process
Subgroups differentiated on the basis of the kind and arrangement of horizons that reflect a conformity to the central concept of the Great Group, a gradation towards another soil Order, or the presence of a special horizon
Family differentiated on the basis of the parent geologic material characteristics such as texture, mineralogy, depth, and/or reaction and on differences in soil climatic factors
Series groupings of pedons with similar arrangements of horizons whose color, texture, structure, consistence, thickness, reaction, and composition fall within relatively narrow and well defined ranges


The Ten Soil Orders of the Canadian System of Soil Classification

Regosolic: Soils having insufficient A or B horizon development to meet the requirements of other orders, perhaps on young parent materials. The order is divided into the Regosol and the Humic Regosol Great Groups.

Chernozemic: Soils that have developed under xerophytic or mesophytic grasses and forbs, or under grassland-forest transition vegetation, in cool to cold, subarid to subhumid climates. These soils have a dark-colored surface (Ah, Ahe, Ap) horizon and a B or C horizon or both, of high base saturation. The order consists of the Brown, Dark Brown, Black, and Dark Gray Great Groups.

Brunisolic: Soils whose horizons are developed sufficiently to exclude the soils from the Regosolic order, but that lack the degrees or kinds of horizon development specified for soils of other orders. These soils, which occur under a wide variety of climatic and vegetative conditions, all have brownish Bm or Btj horizons. The four Great Groups - Melanic Brunisol, Eutric Brunisol, Sombric Brunisol, and Dystric Brunisol - are separated on basis of thickness of Ah horizons and soil reaction.

Gleysolic: Soils developed under wet conditions and permanent or periodic reduction. These soils have low chromas, or prominent mottling, or both, in some horizons. The Gleysol, Humic Gleysol, and Luvic Gleysol are the three Great Groups.

Luvisolic: Soils that may have eluvial (Ae) horizons, and must have illuvial (Bt) horizons in which silicate clay is the main accumulation product. These soils develop under deciduous or mixed forest or forest-grassland transition in a moderate to cool climate. The order is divided into the Gray Luvisol and the Gray Brown Luvisol Great Groups.

Podzolic: Soils of coniferous forests having podzolic B horizons (Bh, Bhf, or Bf) in which combinations of amorphous Al, Fe, and organic matter have accumulated. The sola are acid and the ion exchange capacity of the B horizons is characterized by pH dependent charge. Three Great Groups are Humic Podzol, Ferro-Humic Podzol, and Humo-Ferric Podzol.

Solonetzic: Soils developed mainly under grass or grass-forest vegetative cover in semiarid to subhumid climates. The soils have a stained brownish solonetzic B (Bn or Bnt) horizon and a saline C horizon. The surface may be an Ap, Ah, Ahe, and/or Ae horizon. The order includes the Solonetz, Solodized Solonetz, and Solod Great Groups.

Organic: Soils that have developed in organic deposits. The majority of organic soils are saturated for most of the year. They contain more than 17% organic carbon. The four Great Groups are the Fibrisol, Mesisol, Humisol, and Folisol.

Cryosolic: Mineral or organic soils of sub-arctic and arctic regions that have permafrost within 1 m of the surface (2 m of the surface if more than one-third of the pedon has been strongly cryoturbated, as indicated by disrupted, mixed, or broken horizons). There are three Great Groups - Turbic Cryosol, Static Cryosol, and Organic Cryosol.

Vertisolic: (A newly introduced soil Order) Clay soils that lack the degree of development necessary for other Orders and that have deep, wide cracks at some time during the year and have high bulk density between the cracks. These soils have marked shrink-swell tendencies with changes in soil water content resulting in wedge-shaped aggregates and/or evidence of severe disruption of horizons in the solum.


Simplified Key to Soil Orders

1. Is the Bf, Bhf, or Bh at least 10 cm thick? If this is true, then the soil belongs to Podzolic Order. If false, go to the next step.
2. Is the Bg or Cg within 50 cm of surface? If this is true, then the soil belongs to Gleysolic Order. If false, go to the next step.
3. Is Bn or Bnt horizon present? If this is true, then the soil belongs to Solonetzic Order. If false, go to the next step.
4. Is Chernozemic Ah or Ap present? If this is true, then the soil belongs to Chernozemic Order. . If false, go to the next step.
5. Is Bt horizon present? If this is true, then the soil belongs to Luvisolic Order. If false, go to the next step.
6. Is the Bm at least 5 cm thick? If this is true, then the soil belongs to Brunisolic Order. If false, go to the next step.
7. As all the other possibilities have been eliminated, this soil belongs to the Regosolic Order

Other classification systems can also be applied to soil. For example, the Soil Capability for Agriculture Classification is an example of an interpretive or technical classification. Soil areas are placed into classes (from Class 1 to Class 7) based on the degree of limitation to the production of common agricultural crops. A similar kind of classification exists for forestry.


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Format for citing this page:

Crown, P. H., Palylyk, C. L., and Juma, N. G. Principles, structure and a simplified key of the Canadian Soil Classification System [Online]. (2000, January 5). Available HTTP: http://www.soils.rr.ualberta.ca/SoilsERM/class.html [cite the date you accessed this page].


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