Red-brown soils: composition and characteristics, formation factors

Red-brown soils are the soils of steppe and desert savannahs. They form under short-grass savannas at the transition to tropical deserts. Such soils are often found in Africa, Northern Australia and certain regions of South America. In the upper part of the soil there is 3-1.5% humus. Below lies the illuvial-carbonate layer. Such lands are used as pastures. Under irrigation conditions, they bring good yields.

Composition and specifics of red-brown soils

The main characteristics of such lands are differences in the structure, morphology and properties of horizons. The upper parts of the horizon are usually characterized by a light structure. In the field, the soil is defined as sandy or sandy loam.

The main mass of the soil is pseudosand. It consists of clay and sand particles, which are firmly held together by iron oxides into microaggregates. Considering the physical characteristics of the material, it resembles real sand.

Below is a dense clayey horizon. It is saturated with iron oxides, which make the material micro-aggregated. Then there is a horizon of ferruginous nodules. Even lower is the horizon of ferruginous-calcareous nodules - kankar.

The simultaneous accumulation of iron oxides and lime in the form of nodules is considered a unique phenomenon and occurs exclusively in red-brown soils.

High iron profile makes soil red-orange or brick red. This is considered a characteristic feature of such lands.

Distribution

Such soils are common in the equatorial monsoon belts of the northern and southern hemispheres. The moisture coefficient in these places for 4-6 months a year is 0.6-0.8. The rest of the year it is at the level of 0.3-0.4. Savannas, xerophytic light forests and shrub formations are common in these areas.

Especially widespread red-brown lands are common in Australia, Africa and southeast Asia. They are most commonly found in well-drained high plains. Much less often, such soils can be seen in the mountains.

Shaping factors

For the formation of these types of soil, the following conditions are required:

1. Humid warm to hot climate.
2. Soil-forming rocks - these include products of ferrsiallite-allite or ferrallite composition.
3. Position in terrain that allows for normal drainage and avoids severe erosion.
4. High Biological Cycling Capacity.
5. The age of the relief, which is enough for the formation of ferrallitic weathering products.

Economic use

Red-brown soils today are used as pastures. However, sometimes they are used for the purpose of agriculture. Such soils are suitable for the cultivation of peanuts, corn, cotton.

In the case of poor farming technology and neglect of anti-erosion measures that are typical for countries with such soils, erosion processes are widespread and ecosystem productivity is lost.

In some regions of the world - in particular, in the Sahel region of Africa - these soils are subject to pronounced anthropogenic desertification. Dealing with it is very problematic. This process requires significant capital investments and significant socio-economic transformations.

Red-brown soils are distinguished by a number of significant characteristics and are found only in certain areas of Africa, Australia and Asia. With the right approach, such soils can be used in agriculture.

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