Discuss the types of tropical soils

a) Laterite
In hot wet regions leaching helps to produce a brown soil, which is known a laterite, also referred to as murram in Kenya. In humid tropical regions soil water contains very little organic matter, and such water does not dissolve iron and aluminium hydroxides. Most other minerals however dissolve and these are carried in solution to B-horizon where they are deposited. Ultimately a soil may be formed which is composed mainly of iron and aluminium compounds. This is called laterite. This is usually red in colour and becomes extremely sticky when wet. It is useful material for making bricks since it sets hard on drying. Because it is the end product in the process of weathering, it is almost completely resistant to further weathering and buildings made of it last a very long time. Some laterites are very rich in aluminium compounds and are called bauxite. Bauxite deposits are usually white or grey in colour. Hardpans also occur in laterites. Laterite can form from any type of rock.
In hot deserts and semi-desert regions there is an upward movement of water in the soil. This results in the deposition of mineral matter in the A-horizon. The soils of the dry Savannah are low in humus and generally shallow. They are usually heavily leached, that is the soluble organic nutrients have been washed out of the soil. They may be high in sand, derived from the insoluble quartz component of the underlying rock. The soils of woodland and wooded grassland are moderately high in humus and of medium depth. They are often rich in iron and aluminium oxides, which may form a surface crust or a layer of nodules below the surface known as laterite or murram.

b) Tropical Red Soils/ Highland Soils
The natural vegetation in most of these areas was forest though much of it has now been cleared for cultivation. The soils are relatively high in humus and rather deep except on very steep slopes where they are shallow and rocky. They vary also according to altitude, above about 2000 m; there are brown soils, rather shallow. Between 1500 and 2000 the soils are deeper and more fertile. Especially fertile soils are formed on areas of young volcanic lavas, for example, the red clay loam soils of Central Kenya and the
highlands of northern Tanzania. The red colour is due to a high content of oxidised iron and the soils are also rich in minerals such as magnesium, calcium and potassium. These soils support the growing of coffee, tea and other cash and food crops.

c) Tropical Desert Soils
These are “skeletal” soils, which are very shallow and low in organic material. These are common in north eastern Kenya. Depending on parent material (the underlying rock) they may be stony or sandy. In Marsabit District there are stony soils formed on young volcanic lava plateau, in Wajir and Garissa there are sandy soils. These soils may contain layers or nodules (lumps) of calcrete which is calcium carbonate deposited by
the evaporation of ground water. This is particularly common in areas of limestone rock such as in Mandera District.

d) Tropical Black Soils
This type of soil develops in humid tropical regions, which have volcanic rocks. The soil is rich in calcium carbonate and other minerals, and it is usually very sticky. The black clays are known as ‘vertisols’ or black cotton soils and are particularly formed in areas of poor drainage, i.e. on plains and plateaus. They are quite rich in nutrients and humus but are difficult to cultivate because of their texture. During the dry season, they became very hard and deep cracks form and during the rainy season they become very muddy
and sticky.

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francis1897 answered the question on October 11, 2022 at 08:20