Soil is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air and billions of organisms, most of them microscopic decomposers. Soil forms when life-forms decay, when solid rock weathers and crumbles, and when sediments are deposited by erosion.

Mature soils are arranged in a series of zones called soil horizons, each with a distinct texture and composition that vary in different types of soils. A cross-sectional view of the horizon in a soil is called a "soil profile". Most mature soils have at least three horizons.

Colour tells us a lot about how useful a soil is for growing crops. For example, dark brown or black topsoil is nitrogen rich and high in organic matter. Grey, bright yellow or red topsoils are low in organic matter and will need enrichment to support most crops.

The average size of the spaces or pores in a soil determines soil permeability, i.e. the rate at which water and air move from upper to lower soil layers. Soil permeability is also influenced by soil structure: how soil particles are organised and clumped together. Soils vary in their contents of clay (very fine particles), silt (fine particles), sand (medium size particles), and gravel (course to very course particles). The proportion of the different sizes and types of mineral particles determines the soil texture. Loam soils which are comprised of roughly equal mixtures of clay, sand silt and humus, are the best soils for growing most crops.

Calcarious soils are those that contain free calcium carbonate and can also be regarded as alkaline soils. The term "dystrophic" refers to an imbalance in nutrients. Dystrophic soils are therefore soils that are rich in humus, giving them a brown colour. They have variable amounts of nutrients and are sometimes depleted of oxygen owing to the high concentration of humus. Eutrophic soils contain large or excessive supplies of nutrients (mostly nitrates and phosphates). Mesotrophic soils (the term is derived from the Greek word "mesos", meaning middle) are neither nutrient rich nor nutrient poor. The term "leaching" refers to a process whereby various soil components are dissolved by water moving through the upper layers, carrying the dissolved material to lower layers. Highly leached soils are those where most of the nutrients, etc. have been leached from the upper layers.

The following data sets can be viewed:

General soil description
Soil depth classes
Clay classes of the topsoil
Leaching status classes

GENERAL SOIL DESCRIPTION:
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Eastern Cape
Free State
Gauteng
KwaZulu-Natal
Mpumalanga
Northern Cape
Northern Province
North West
Western Cape

SOIL DEPTH CLASSES
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Eastern Cape
Free State
Gauteng
KwaZulu-Natal
Mpumalanga
Northern Cape
Northern Province
North West
Western Cape

 

Population pressure on soil resources High population densities in areas of highly erodible soils have resulted in devastating soil erosion occurring in many areas of South Africa, compromising the ability of this resource to sustain vegetation, animals and people in those areas. The areas of high susceptibility to soil erosion and high population density represent the worst crisis areas. Large areas of average to high soil erosion susceptibility, coinciding with areas of high population densities, exist in both the metropolitan and the rural areas in South Africa.

CLAY CLASSES OF THE TOPSOIL
Choose a province to view map or click on province in image

Eastern Cape
Free State
Gauteng
KwaZulu-Natal
Mpumalanga
Northern Cape
Northern Province
North West
Western Cape

LEACHING STATUS CLASSES:
Choose a province to view map or click on province in image

Eastern Cape
Free State
Gauteng
KwaZulu-Natal
Mpumalanga
Northern Cape
Northern Province
North West
Western Cape