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horizons: Mineral horizons in which the main feature is loss of silicate clay, iron aluminum, or some combination of these, leaving a concentration of sand and silt particles of quartz or other resistant minerals.
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Our section is designed to be used in conjunction with a field guide for describing soil morphology such as Section 3 of this Field Handbook, Soils Illustrated by Kent Watson, The Field Guide for Describing Soils in Ontario, or the CanSIS Manual for Describing Soils in the Field (available on-‐lin...
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A soil profile contains three main horizons. They are named as horizon A, horizon B and horizon C. . The surface soil or that layer of soil at the top which is liable to leaching and from which some soil constituents have been removed is known as horizon A or the horizon of eluviation.
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The description of mottled soil horizons needs to include the color of the matrix and the color, or colors, of the principal mottles plus a description of the pattern of mottling.
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- O Horizon –
- A Horizon –
- E Horizon –
- B Horizon –
- C Horizon –
- R Horizon –
‘O’ is for organic. This layer is the uppermost layer of the soil rich in organic matter, such as the remains of plants and dead animals. Due to high organic content, this layer is typically black brown or dark brown. The O horizon is thin in some soil, thick in some others, or absent in the rest.
Found below the O horizon, it has a dark brown color as it contains the maximum organic matter of the soil. The A horizon or topsoil is thus also called the humus layer. The topsoil is the region of intense biological activity and has the most nutrients. Insects, earthworms, centipedes, bacteria, fungi, and other animals are found inside this layer...
This layer consists of nutrients leached from O and A horizons and is thus called the eluviations layer. Leaching of clay, minerals, and organic matter leavesthis layer with a high concentration of sand, slit particles, quartz, and other resistant materials. E horizon is absent in most soils but is more common in forested areas.
Mostly found below the topsoil is another layer called the subsoil or horizon B. It is lighter in color than the topsoil due to lower humus content. However, it is comparatively more rigid and compact than the topsoil. This layer has less organic content but is rich in minerals that are leached down from the topsoil. The subsoil is the region of de...
Also known as regolith or saprolite, it lies just below the subsoil. It is called the parent rock because all the upper layers developed from this layer. C horizon is devoid of any organic matter and is made of broken-up bedrocks, making it hard. Plantroots do not penetrate this layer. This layer is a transition between the inner layer of earth and...
Found beneath all the layers, it consists of un-weathered igneous, sedimentary, and metamorphic rocks. It is highly compact. Granite, basalt, quartzite, sandstone, and limestone make up the bedrock.
Soil horizons are the layers in a soil profile used to classify soil types. Horizons based on color, texture, roots, structure, rock fragments, and any unique characteristic worth noting. Master Soil Horizons are depicted by a capital letter in the order (from top down): O, A, E, B, C, and R.
SOIL HORIZONS There are three primary soil horizons, called master horizons. They are A, B, and C. These are part of a system for naming soil horizons in which each layer is identified by a code: O, A, E, B, C, and R. The O horizon is an organic layer made up of partially decayed plant and animal debris. It
