The tiers of Organic soils are also considered as layers. Unconforming layers below the control section that do not appear to have been affected by pedogenic processes are considered as layers. Thus the following are considered as horizons: C(IC), any unconforming layer within the control section, and any unconforming layer below the control section that has been affected by pedogenic processes (e.g., IIBc, IIIBtj). In practice, it is usually difficult to determine the lower boundary of soil material affected by soil-forming processes. Theoretically a IIC affected by soil-forming processes is a horizon for example a IICca is a horizon. below the control section that are unaffected by soil-forming processes.

The layers defined are R, rock W, water and IIC or other nonconforming, unconsolidated mineral layers, IIIC, etc. Some other methods pertaining to organic horizons are outlined near the end of this chapter. Many of the laboratory methods required are outlined in a publication sponsored by the Canadian Society of Soil Science (Carter 1993). However, in cases of weak expression or of borderline properties, as between Ah and H, laboratory determinations are necessary before horizons can be designated positively. Well-developed horizons are readily identified in the field. Subdivisions of horizons are labeled by adding lower-case suffixes to some of the major horizon symbols as with Ah or Ae. The major organic horizons are L, F, and H, which are mainly forest litter at various stages of decomposition, and O, which is derived mainly from wetland vegetation. The major mineral horizons are A, B, and C. In previous editions of this publication and in the Glossary of Terms in Soil Science (Canada Department of Agriculture 1976) organic materials are designated as layers and not horizons. For the sake of brevity these other layers are referred to simply as layers but it is recognized that soil horizons are also layers.

The other layers are either nonsoil layers such as rock and water or layers of unconsolidated material considered to be unaffected by soil-forming processes. It differs from adjacent horizons in properties such as color, structure, texture, and consistence and in chemical, biological, or mineralogical composition. A soil horizon is a layer of mineral or organic soil material approximately parallel to the land surface that has characteristics altered by processes of soil formation. Therefore, the clear definition and designation of soil horizons and other layers are basic to soil classification. The definitions of taxa in the Canadian system are based mainly on the kinds, degree of development, and the sequence of soil horizons and other layers in pedons. Previous | Table of Contents | Next Soil Horizons and Other Layers

Canadian System of Soil Classification, 3rd editionĬhapter 2: Soil, Pedon, Control Section, and Soil Horizons (continued).

Soil profile and soil horizon definition