Discuss the classifications of soil types in Africa

Within the African Continent and also globally soil formation depends on soil
forming agents of:
(a) Parent rocks.
(b) Climatic conditions of a given area
(c) Organic matter
(d) Relief of an area
In this case the parent rock plays an outstanding role in soil formation in any area
on the earth.
Therefore the soil types in Africa are formed and distributed according to the rock
formation or in other words depending on the geological formation in various regions.
In Africa there are about five soil groups (sometime referred as soil types) as
follows:-
(a) Laterite and latosolic soils.
(b) Red loams.
(c) Dark Grey and Black soils.
(d) Desert Soils.
(e) Other types or groups like catenary systems or complexes.
(a) Laterite and Latosolic soils are usually developed in Equatorial and partly
savannah areas of Africa and other similar zones.
More examples occupy the northern parts of Congo Basin, Madagascar and in
patches to the Western coasts of Africa.
These are heavily leached soils containing salts and silica.
Most of their horizons have much aluminium plus iron oxides with reddish colour.
When exposed immediately it is soft but as it is heat by the sun it sets brick-hard
structures.
Aluminium minerals usually dominate other surface minerals.
(b) Red loams – This type is also found mostly in tropics occupying or developing on
rolling and dissected landforms originating granites or sandstones as parent rocks.
This type/group develops in humid savannah areas which are not heavily leached.
The colour is dark-red to brown usually fertile enough rich in ferrous oxides and
silica.
On soil maps this type is identified as reddish-brown, reddish cluesnut, brown
soils.
It occupies or found or develops on high areas as on Ethiopian plateau, high
central parts of South Africa including Orange Range, central part of the Atlas Mountains
(c) Dark Grey and Black Soils – develop on flat plains on dark-coloured igneous
rocks.
These are heavy textured soils with lime content especially in top horizons.
These are heavy textured soils with lime content especially in op horizons.
They dry and crack during dry seasons, and stick easily.
In East Africa and particularly in Kenya they are known as Black clays
(grumosolic soils) or Black cotton soils that classified by UNESCO as Uley soils.
They develop in low-lying plains known sometimes as cotton lands such as Mwea
area in the South of Mount Kenya, Kano plains around Lake Victoria, Athi River plains
East of Nairobi and in places these soils appear in patches in depression-like structures.
(d) Desert Soils – This type has no leaching capacity because the climatic conditions
in such areas.
The upper horizons are usually thin, stony or sandy.
The colour is yellowish – grey to reddish brown having no humus with high lime
content.
These soils originate from Aeolian aerials which don’t relate to any rock as they
are formed or developed within alkaline conditions; especially in places where water has
evaporated in pans and leaves thick accumulations of minerals as those areas of northeastern parts of Kenya.
(e) Other types/groups; as catenary systems or complexes – (Minor soil types)
These are brown earths which are dark brown in colour, loamy to sandy.
In this type there are also the Rendizina and Terra Rossa soils developed on the
northern low slopes of the Atlas Mountains, and other Island-like hills in or within the
Sahara Desert.
They are defined as reddish residual clay soils rich in iron materials that
accumulate in depressions in limestone countries or areas or regions under a semi-arid or
summer drought conditions like in Mediterranean region, Yugoslavia country, Southern
Italy region, and limestone countries in Britain.
(ii) There are other minor soil types called sometimes as mountain soils which are on
various soil maps indicated mainly on the high altitudes or on top peaks.
About ½ of all the land area between the Tropics of Cancer and Capricorn lies in
the continent of Africa/J.D’Hoore, 1964).
Therefore soil classification of Africa should be fairly representative of the intertropical belt.
Several attempts to classify tropical soils have been made:-
Some classification systems were extrapolations (no prove ) based on
generalizations obtained in temperate areas which were of little practical use.
Others originated in the tropics, but could be applied only to limited areas, since plant
production was their main concern and the criteria were agronomic rather than
pedogenetic.
Africa has an area of about 30.3 million Km^2.

Out of this area about 20 million Km^2 contains soil cover – i.e. covered by some
soil layer.
Such a surface layer carries vegetation of some different kinds. Some surfaces are
bare possibly because human activities, such as cultivation and settlements have been
practiced on the Earth’s surface, where possible. The rest of the area is stony desert, bare
rock, broken rock material, open water and at very high altitudes including glacial ice and
perpetual snow totaling to about 1/3 of the continent.
Much of the African area is poor and the growth of natural vegetation and rapid
regeneration of bush or forest following clearing tend to conceal the intrinsic soil
poverty.
A large area of Africa rainfall is so low or so erratic and this makes cultivation a
leading hazardous.
As well this causes heavy teaching as well as loosing soil structure over the
continent.
The soil poverty as well is caused by poor parent materials, i.e. lava boulders,
Rock outcrops, ice or extensive sand-like oceans in a number of deserts of Africa.
Also some soil types are formed out of materials that are derived from old, acid
parent rocks, poor in calcium and nutrients of which the average organic content of
African soils is only 0.2% if compared to 2.0% for the cultivated soils of some parts of
Europe.

---

Titany answered the question on January 17, 2022 at 13:27