Subsoil Horizons

Well-Drained Subsoils

Red Apedal B Horizon

This horizon has red colours and a weak, cheese-like structure and underlies a topsoil horizon or a yellow-brown apedal B horizon. It is suitable for intensive utilisation.

Yellow-Brown Apedal B Horizon

This horizon is yellow-brown in colour and underlies diagnostic topsoil or an E horizon. It is high-potential soil.

Red Structured B Horizon

This horizon has red colours, a relatively strong structure and underlies an orthic B horizon. It is a high-potential soil, occurring mainly in low rainfall areas and responds to irrigation.

Neocutanic B Borizon

This horizon occurs in unconsolidated colluvium, underlies diagnostic topsoil or an E horizon and contains non-uniform colours, caused by cutans (clay skins). It is usually deep soil, suitable for irrigation.

Neocarbonate B Horizon

This horizon occurs in unconsolidated material, underlies diagnostic topsoil or an E horizon and contains enough calcium magnesium carbonate to effervesce when treated with hydrochloric acid. It is a suitable arable soil.

Hydromorphic Subsoils

E Horizon

This horizon underlies an A horizon. It is grey or mottled in colour because of leaching due to the impervious nature of the underlying subsoil, causing water to build up and move sideways. It is highly susceptible to erosion.

G Horizon

This horizon underlies a vertic, melanic or orthic A or E horizon. It is saturated with water for long periods. It is often used for winter pastures but is susceptible to erosion if exposed.

Soft Plinthic B Horizon

This horizon has a mottled matrix with concretions and occurs second or third in the sequence of a diagnostic horizon, provided that when it is third, the second horizon is an E, red apedal B or a yellow-brown apedal B horizon. When it underlies yellow-brown soil, it acts as a water reservoir.

Hard Plinthic B Horizon

This horizon consists of mottled concretions that cannot be cut with a spade. It occurs beneath an orthic A, E, or yellow-brown apedal B horizon. It has low cropping potential.

Unspecified Wet Material

This horizon underlies red apedal, yellow-brown apedal, neocutanic or neocarbonate B horizons. It varies from grey unconsolidated soil to partly weathered rock.

Restrictive Cutanic Subsoils

Prismacutanic B Horizon

This horizon has a prismatic or columnar structure and an abrupt transition with an overlying orthic A or E horizon. It is only suitable for natural grazing.

Pedocutanic B Horizon

This horizon has an angular blocky structure, underlying a diagnostic topsoil horizon or an E horizon. It should be used for natural grazing or pastures.

Lithocutanic B Horizon

This horizon has a cutanic character expressed usually as tongues merging into the underlying rock. It underlies a diagnostic topsoil horizon or an E horizon. It has a deep topsoil and is suitable for cropping.

Young Subsoils

Hard Rock

This is a continuous hard layer of rock and occurs beneath a diagnostic melanic or an orthic A horizon.

Stratified Alluvium

This is unconsolidated material, contains stratifications caused by alluvial or colluvial deposits and underlies an orthic A or melanic A horizon or occurs at the surface. It is suitable for irrigation.

Regic Sand

This is a recent sand deposit, usually Aeolian, which shows little pedogenesis, and directly underlies an orthic A horizon.

Man-Made Soil Deposit

This is a man-made deposit of soil material and occurs beneath an orthic A horizon or at the surface.

Material Underlying Pedocutanic B Subsoil’s

Saprolite

This is a horizon of weathering rock underlying a pedocutanic B horizon. It is non-arable and best left as grazing.

Unconsolidated material without signs of wetness

This underlies a pedocutanic B horizon and is not suitable for cultivation. It is best left for natural grazing.

Unconsolidated material with signs of wetness

This underlies a pedocutanic B horizon and is non-arable.

General assessment of some selected soil forms

There are 73 different soil forms in South Africa, derived from 30 soil horizons. Soil ranking, according to decreasing potential and increasing hazards, is shown below.