Chapter 16: Correlation of Canadian Soil Taxonomy with Other Systems
The approximate equivalents of the soil horizons and taxa in the Canadian system are given for the U.S. system (Soil Survey Staff 1994) and in the terminology of the FAD-UNESCO soil map of the world (Food and Agriculture Organization of the United Nations 1985). The horizon designations and terms are rarely exactly equivalent. The definitions of soil horizons and soil taxa differ from one system to another.
The U.S. system includes a category named suborder that is not in the Canadian system, and the FAO soil units are arranged into only two categories. Thus the categorical levels of the related taxa are generally not equivalent. The closest approximation to equivalence of taxa is in the case of Organic soils (Canadian) and Histosols (U.S.). Great groups and subgroups of Organic soils are nearly equivalent to the corresponding suborder and great groups of Histosols. This correspondence resulted from United States and Canadian pedologists working together to develop taxonomy for Organic soils. However, even in this case there are differences. For example, the organic matter content required for Histosols differs somewhat from that required for soils of the Organic order.
In other orders, differences in the approximately equivalent taxa are greater. For example, most Chernozemic soils are Mollisols, but some are Aridisols. Many Mollisols are Chernozemic soils, but some are Gleysolic soils, others are Solonetzs, and still others are Melanic Brunisols. There are also basic differences between Podzolic soils and Spodosols. Most Podzolic soils are Spodosols, but a significant proportion are Inceptisols because a spodic horizon must be dominated more by amorphous material than a Podzolic B horizon. Conversely, a few Podzolic Luvisols are Spodosols. All Vertisolic soils would qualify as Vertisols. However, all Vertisols would not be Vertisolic because Vertisolic soils must have a layer affected by argillipedoturbation as well as slickensides and cracks. At lower levels in the systems, differences become progressively greater.
Tables 6, 7, and 8 provide some idea of how soil horizon designations and soil taxa are related at the upper levels in the three systems. The tables have been revised from those prepared by J.S. Clayton for previous editions of the Canadian System of Soil Classification. Revisions were required because of some changes in horizon designations and in the definitions of horizons and taxa in both the Canadian and U.S. systems. Correlation at the subgroup level is not presented.
The tables are not adequate for correlating either the horizon designations or the taxonomy of a given pedon as expressed in one system with those of another system. Adequate correlation requires knowing the criteria and definitions in the systems involved.
1. Canadian | 2. U.S. | 3. FAO | Comments |
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* 17% organic C equals about 30% organic matter. ** Fep: Fe extractible in pyrophosphate |
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O | O | H | 1 (Can. Limit): organic horizon (O) >17% organic C. * 2 & 3 (U.S. and FAO limits): lower limit of organic horizons ranges proportionately from 20% OM with 0% clay to 30% OM with >50% clay |
Of | Oi | H | 1 (Can. Limit): organic horizon (O) >17% organic C. * 2 & 3 (U.S. and FAO limits): lower limit of organic horizons ranges proportionately from 20% OM with 0% clay to 30% OM with >50% clay |
Om | Oe | H | 1 (Can. Limit): organic horizon (O) >17% organic C. * 2 & 3 (U.S. and FAO limits): lower limit of organic horizons ranges proportionately from 20% OM with 0% clay to 30% OM with >50% clay |
Oh | Oa | H | 1 (Can. Limit): organic horizon (O) >17% organic C. * 2 & 3 (U.S. and FAO limits): lower limit of organic horizons ranges proportionately from 20% OM with 0% clay to 30% OM with >50% clay |
Oco | Oa | H | Coprogenous limnic material |
L-F | Oi-Oe | O | Generally not saturated with water for prolonged periods |
L-H | Oi-Oa | O | --- |
F-H | Oe-Oa | O | --- |
A | A | A | 1: ≤17% organic C; 2 & 3: upper limit of OM ranges proportionately from 20% OM with 0% clay to 30% OM with clay >50% |
Ah | A | Ah | 1: ≤17% organic C; 2 & 3: upper limit of OM ranges proportionately from 20% OM with 0% clay to 30% OM with clay >50% |
Ahe | AE | (Ah-E) | 1: ≤17% organic C; 2 & 3: upper limit of OM ranges proportionately from 20% OM with 0% clay to 30% OM with clay >50% |
Ae | E | E | --- |
Ap | Ap | Ap | --- |
AB | AB or EB | AB or EB | Transitional horizons |
BA | BA or BE | BA or BE | --- |
A & B | A & B | A/B | Interfingered horizons |
AC | AC | A/C | --- |
B | B | B | --- |
Bt | Bt | Bt | --- |
Bf | Bs | Bs | 1: specific limits; 2 & 3: no specific limit |
Bhf | Bhs | Bhs | 1: >5% organic C |
Bgf | Bgs | Bgs | --- |
Bh | Bh | Bh | 1: Specific C to Fep ratio; 2&3: no specific C to Fep ratio |
Bn | Bn | Bn | --- |
Bm | Bw | Bw | --- |
C | C | C | --- |
IIC | 2C | IIC | --- |
R | R | R | --- |
W | --- | --- | Water |
other suffixes | May be used with A, B, or C horizons | ||
b | b | b | 1 & 2: buried; 3: buried or bisequa |
c | m | m | --- |
ca | k | k | Accumulation of carbonates |
--- | y | y | Accumulation of gypsum |
cc | m | c | --- |
g | g | g or r | 3: g - mottling, - strong reduction |
j | --- | --- | --- |
k | --- | --- | Indicates presence of carbonate |
--- | v | --- | Plinthite |
--- | q | q | Silica accumulation |
s | z | z | Visible salts |
ss | ss | --- | Indicates presence of slickensides |
sa | y or z | y or z | 1: includes gypsum; 2 & 3: y - gypsum, z - other more soluble salts |
--- | o | --- | Residual sequioxide concentration |
u | --- | --- | Turbic |
--- | --- | u | Unspecified |
v | --- | --- | Vertic Horizon |
x | x | x | Fragipan |
y | --- | --- | Cryoturbation |
z | f | I | Permafrost layer |
1. U.S. | 2. FAO | 3. Canadian | Comments |
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Mollic Epipedon | Mollic A | Chernozemic A | With high base status |
Anthropic Epipedon | Mollic A | Cultivated Chernozemic A | --- |
Umbric Epipedon | Umbric A | Ah | With low base status |
Histic Epipedon | Histic H | Of, Om, Oh | --- |
Ochric Epipedon | Ochric A | light-colored A | --- |
Plaggen Epipedon | --- | Ap | --- |
Albic horizon | Albic E | Ae | --- |
Argillic horizon | Argillic B | Bt | --- |
Agric horizon | Argillic B | Illuvial B | Formed under cultivation |
Natric horizon | Natric B | Bn or Bnt | --- |
Spodic horizon | Spodic B | podzolic B | --- |
Cambic horizon | Cambic B | Bm, Bg, Btj | --- |
Oxic horizon | Oxic B | --- | --- |
Duripan | m | c | --- |
Durinodes | --- | cc | --- |
Fragipan | x | Fragipan | --- |
Calcic horizon | Calcic horizon | Bca or Cca | --- |
Petrocalcic | Bkm | Bcac or Ccac | --- |
Gypsic | Gypsic | Asa, Bsa, Csa | 3. Only if sa horizon is dominantly CaSO4 |
Salic | --- | Asa, Bsa, Csa | --- |
Placic | Thin iron pan | Placic | --- |
Plinthite | Plinthite | --- | --- |
Lithic contact | --- | Lithic contact | --- |
Paralithic contact | --- | IICc | --- |
g | Gleyic horizon | g | --- |
--- | sulfuric horizon | --- | Low pH, jarosite mottles |
Canadian System | U.S. Soil Taxonomy | WRB(FAO) [2] System |
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[1] Only the nearest equivalents are indicated [2] World Reference Base for Soil Resources (Deckers et al. 1998) |
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Chernozemic | Borolls | Kastanozem, Chernozem, Greyzem, Phaeozem |
Brown Chernozem | Aridic Boroll subgroups | Kastanozem (aridic) |
Dark Brown Chernozem | Typic Boroll subgroups | Kastanozem (Haplic) |
Black Chernozem | Udic Boroll subgroups | Chernozem |
Dark Grey Chernozem | Boralfic Boroll subgroups, Albolls | Greyzem |
Solonetzic | Natric great groups, Mollisols & Alfisols | Solonetz |
Solonetz | Natric great groups, Mollisols & Alfisols | Mollic, Haplic, or Gleyic Solonetz |
Solodized Solonetz | Natric great groups, Mollisols & Alfisols | Mollic, Haplic, or Gleyic Solonetz |
Solod | Glossic Natriborolls, Natralbolls | Solodic Planosol |
Vertic Solonetz | Haplocryerts | Sodic Vertisol |
Luvisolic | Boralfs & Udalfs | Luvisol |
Gray Brown Luvisol | Hapludalfs or Glossudalfs | Albic Luvisol, Haplic Luvisol |
Gray Luvisol | Boralfs | Albic Luvisol, Gleyed Luvisol |
Podzolic | Spodosols, some Inceptisols | Podzol |
Humic Podzol | Cryaquods, Humods | Humic Podzol |
Ferro-Humic Podzol | Humic Cryorthods, Humic Haplorthods | Orthic Podzol |
Humo-Ferric Podzol | Cryorthods, Haplorthods | Orthic Podzol |
Brunisolic | Inceptisols, some Psamments | Cambisol |
Melanic Brunisol | Cryochrepts, Eutrochrepts, Hapludolls | Cambisol, Eutric Cambisol |
Eutric Brunisol | Cryochrepts, Eutrochrepts | Eutric Cambisol, Calcic Cambisol |
Sombric Brunisol | Humbric Dystrochrepts | Dystric Cambisol, Umbric Cambisol |
Dystric Brunisol | Dystrochrepts, Cryochrepts | Dystric Cambisol |
Regosolic | Entisols | Fluvisol, Regosol |
Regosol | Entisols | Regosol |
Humic Regosol | Entisols | Fluvisol, Regosol |
Gleysolic | Aqu-suborders | Gleysol, Planosol |
Humic Gleysol | Aquolls, Humaquepts | Mollic, Umbric, Calcic Gleysol |
Gleysol | Aquents, Fluvents, Aquepts | Eutric, Dystric Gleysol |
Luvic Gleysol | Argialbolls, Argiaquolls, Aqualfs | Planosol |
Organic | Histosols | Histosol |
Fibrisol | Fibrists | Histosol |
Mesisol | Hemists | Histosol |
Humisol | Saprists | Histosol |
Folisol | Folists | Histosol |
Cryosolic | Gelisols | Cryosol |
Turbic Cryosol | Turbels | Cryosol |
Static Cryosol | Orthels | Cryosol |
Organic Cryosol | Histels | Cryic Histosol |
Vertisolic | Cryerts | Vertisol |
Vertisol | Haplocryerts | Calcic Vertisol, Eutric Vertisol |
Humic Vertisol | Humicryerts | Dystric Vertisol |
Source: The Canadian System of Soil Classification (Third Edition)