Horizon Master Code

Attribute definition
Attribute Label HZN_MAS
Title Horizon Master Code
Description

Identifies the master horizon, as per Chapter 2 of the Canadian System of Soil Classification, third edition.

Classes Horizon Master Code: 21 classes.


Mineral
Code Class Description
A Surface mineral horizon

This mineral horizon forms at or near the surface in the zone of leaching or eluviation of materials in solution or suspension, or of maximum in situ accumulation of organic matter or both. The accumulated organic matter is usually expressed morphologically by a darkening of the surface soil (Ah). Conversely, the removal of organic matter is usually expressed by a lightening of the soil color usually in the upper part of the solum (Ae). The removal of clay from the upper part of the solum (Ae) is expressed by a coarser soil texture relative to the underlying subsoil layers. The removal of iron is indicated usually by a paler or less red soil color in the upper part of the solum (Ae) relative to the lower part of the subsoil.

AB Surface transitional horizon

Gradual transition. The dominance of horizons in the transitional zone may be shown by order, AB or BA, etc. Lower case suffixes may also be added in some instances, e.g., ABg, ABgj, etc.

AC Surface transitional horizon

Gradual transition. The dominance of horizons in the transitional zone may be shown by order, AC or BC, etc. Lower case suffixes may also be added in some instances, e.g., ACg, ACgj, etc.

B Subsurface mineral horizon

This mineral horizon is characterized by enrichment in organic matter, sesquioxides, or clay; or by the development of soil structure; or by a change of color denoting hydrolysis, reduction, or oxidation. In B horizons, accumulated organic matter (Bh) is evidenced usually by dark colors relative to the C horizon. Clay accumulation is indicated by finer soil textures and by clay cutans coating peds and lining pores (Bt). Soil structure developed in B horizons includes prismatic or columnar units with coatings or stainings and significant amounts of exchangeable sodium (Bn) and other changes of structure (Bm) from that of the parent material. Color changes include relatively uniform browning due to oxidation of iron (Bm), and mottling and gleying of structurally altered material associated with periodic reduction (Bg).

BA Subsurface Transitional Horizon

Gradual transition. The dominance of horizons in the transitional zone may be shown by order, AB or BA, etc. Lower case suffixes may also be added in some instances, e.g., BAg, BAgj, etc.

BC Subsurface Transitional Horizon

Gradual transition. The dominance of horizons in the transitional zone may be shown by order, AC or BC, etc. Lower case suffixes may also be added in some instances, e.g., BCg, BCgj, etc.

C Parent mineral horizon

This mineral horizon is comparatively unaffected by the pedogenic processes operating in A and B horizons, except the process of gleying (Cg), and the accumulation of calcium and magnesium carbonates (Cca) and more soluble salts (Cs, Csa). Marl, diatomaceous earth, and rock with a hardness ≤3 on Mohs' scale are considered to be C horizons.

CA
CB


Organic
Code Class Description
F Organic horizon partially decomposed

This organic horizon is characterized by an accumulation of partly decomposed organic matter. Some of the original structures are difficult to recognize. The material may be partly comminuted by soil fauna as in moder, or it may be a partly decomposed mat permeated by fungal hyphae as in mor.

FH
H Organic horizon of indiscernible origin

This organic horizon is characterized by an accumulation of decomposed organic matter in which the original structures are indiscernible. This horizon differs from the F by having greater humification due chiefly to the action of organisms. It is frequently intermixed with mineral grains, especially near the junction with a mineral horizon.

L Organic horizon poorly decomposed

This organic horizon is characterized by an accumulation of organic matter in which the original structures are easily discernible.

LF
LFH
LH
O Organic horizon from mosses, rushes and woody materials

This organic horizon is developed mainly from mosses, rushes, and woody materials.



Other
Code Class Description
R Rock

This consolidated bedrock layer is too hard to break with the hands (>3 on Mohs' scale) or to dig with a spade when moist. It does not meet the requirements of a C horizon. The boundary between the R layer and any overlying unconsolidated material is called a lithic contact.

W Water

This layer of water may occur in Gleysolic, Organic, or Cryosolic soils. Hydric layers in Organic soils are a kind of W layer as is segregated ice formation in Cryosolic soils.

- Not applicable