Chapter 15: Soil Phase

Class W1, slightly eroded phase

As much as 25% of the original A horizon may have been removed from most of the area. In most cases the soils eroded to this degree are not significantly different in use capabilities and management requirements from noneroded soils.

Class W2, moderately eroded phase

Between 25 and 75% of the original A horizon may have been lost from most of the area. The present Ap horizon consists of a mixture of the underlying soil and the original A horizon. Shallow gullies may be present.

Class W3, severely eroded phase

More than 75% of the original A horizon and commonly part of the next underlying horizon have been lost from most of the area. Shallow gullies are common and a few deep ones may occur.

Class W4, gullied land phase

The land is dissected by moderately deep to deep gullies with small areas of intact soil between the gullies. The area is unsuitable for crop production without reclamation.

Class D1, slightly wind-eroded phase

Wind has removed between 25 and 75% of the original A horizon and tillage results in mixing of subsurface material with remnants of the original surface layer.

Class D2, severely wind-eroded phase

Wind has removed more than 75% of the original A horizon and commomly part of the underlying horizon.

Class D3, blown-out land phase

Wind has removed most of the solum and numerous blowout holes are carved into the parent material. Some areas between blowouts are deeply burried by soil material from the blowouts. The area is unsuitable for crop production without extensive reclamation.

Overblown phase

Deposits of wind-eroded materials on the soil surface are great enough to influence management but are not great enough to destroy the essential characteristics of the soil series.

Overwash phase

Deposits of water-eroded materials on the soil surface are thick enough to influence management requirements significantly but are not deep enough to destroy the essential characteristics of the soil series.

Class S0, nonstony phase

No stones or too few are present to interfere with cultivation (<0.01% of surface, stones more than 25 m apart).

Class S1, slightly stony phase

Some stones are present that hinder cultivation slightly or not at all (0.01-0.1% of surface, stones 8-25 m apart).

Class S2, moderately stony phase

Enough stones are present to cause some interference with cultivation (0.1-3% of surface, stones 1-8 m apart).

Class S3, very stony phase

There are sufficient stones to handicap cultivation seriously; some clearing is required (3-15% of surface, stones 0.5-1 m apart).

Class S4, exceedingly stony phase

The stones prevent cultivation until considerable clearing is done (15-50% of surface, stones 0.1-0.5 m apart).

Class S5, excessively stony phase

The land surface is too stony to permit cultivation; it is boulder or stone pavement (more than 50% of surface, stones less than 0.1 m apart).

Class R0, nonrocky phase

Bedrock exposures do not interfere seriously with tillage. Exposures, if present, are generally more than 100 m apart and cover less than 2% of the surface.

Class R1, slightly rocky phase

The bedrock exposures interfere with tillage but not enough to make intertilled crops impracticable. Depending on the pattern and how it affects tillage, rock exposures are roughly 35-100 m apart and cover 2-10% of the surface.

Class R2, moderately rocky phase

The bedrock exposures make tillage of intertilled crops impracticable, but the soil can be worked for hay crops or improved pasture if other soil characteristics are favorable. Rock exposures are roughly 10-35 m apart and cover about 10-25% of the surface depending on the pattern.

Class R3, very rocky phase

The rock outcrops make all use of machinery impracticable, except for small machinery. Where other soil characteristics are favorable the land may have some use for native pasture or forests. Rock exposures or patches of soil too thin over rock for use are roughly 3.5-10 m apart and cover 25-50% of the surface depending on the pattern.

Class R4, exceedingly rocky phase

Sufficient rock outcrop or insufficient depth of soil over rock makes all use of machinery impracticable. The land may have some value for poor pasture or forestry. Rock outcrops are less than 3.5 m apart and cover 50-90% of the area.

Class R5, excessively rocky phase

More than 90% of the land surface is exposed bedrock (rock outcrop).

Family criteria

Definitions are given in Chapter 14.

Particle size e.g., Humo-Ferric Podzols, fragmental phase. The textural class of the mineral surface layer of a soil series may also be indicated as a phase, e.g., Breton silt loam.

Substitute classes (particle size) e.g., Dystric Brunisols, cindery phase.

Mineralogy e.g., Black, smectitic phase.

Depth e.g., Regosols, shallow lithic phase (lithic contact 50-100 cm from the mineral surface); Organic Cryosols, very shallow cryic phase (permafrost layer at 40-100 cm).

Reaction e.g., Regosols, alkaline phase.

Calcareous e.g., Rego Dark Brown Chernozem, extremely calcareous phase.

Soil climate e.g., Podzolic, cold, perhumid phase.

Other family criteria for Organic soils that may be used as phases of higher categories are characteristics of the surface tier, e.g., Mesisols, fine loamy phase; reaction, e.g., Typic Fibrisols, dysic phase; and kind of limnic material, e.g., Limnic Mesisol, diatomaceous phase.

Series criteria

Physical disruption e.g., Humo-Ferric Podzol, turbic phase.

Salinity e.g., Orthic Brown Chernozem, saline phase.

Influence of volcanic ash e.g., Orthic Dystric Brunisol, andic phase.

Secondary carbonates in the A horizon e.g., Orthic Brown Chernozem, carbonated phase.

Other series differentiae may also be named as phases of higher categories.

Also, subgroup differentiae may be used to indicate phases of classes at the order level, e.g., Podzolic soils, gleyed phase.

Source: The Canadian System of Soil Classification (Third Edition)