Soils of the subtropics: classification and specifics, is there any application in Russia

On the planet, some climatic zones replace others. They differ not only in temperature conditions and humidity levels, but also in the quality, composition and even color of the soil. Due to the complex geographical location and the specifics of vegetation, the soils of the tropics and subtropics have been poorly studied until recently. They are characterized by low fertility and characteristic yellowish, orange and reddish hues.

Specifics

Soils of the subtropics and humid tropics occupy only 23% of the total land area on the globe. On the territory of the Russian Federation, soils of this kind are practically not found. The subtropics occupy smaller areas than the tropics.

The following factors influence the formation of these types of soils:

• Climate. There are long summers with high temperatures and high rainfall, short and warm winters. The ground never freezes, and the tropics never freeze.
• Soil-forming rocks. All local rocks have undergone strong weathering. Igneous rocks predominate in mountainous areas, alluvial and deluvial-proluvial rocks predominate in lowlands.
• Relief. Basically, the elevations here do not exceed 600 meters. Elevation differences provide pronounced erosion processes on the slopes and significant waterlogging of soils at the foot and in the valleys.
• Vegetation. In these zones, due to the large amount of heat and moisture, plants grow rapidly, actively and in large quantities. The green mass grows during the wet season, and then the plants suffer from drought. This leads to the death of the vegetation layer, the fall of foliage, which forms a layer of humus.

The soils of these zones are characterized by reddish and yellowish tints, the formation of yellow, orange and red colors based on rocks, not too much humus with a poorly formed horizon. As wet and dry seasons alternate, a layer of organic deposits forms quickly.

Classification of subtropical and tropical soils

All varieties of soils in tropical and subtropical regions are divided into the following types:

Krasnozems

Red soils are formed on the basis of rocks of volcanic origin, which contain a significant amount of magnesium, iron and alumina, which determines their specific shades. The bedrock layer can reach a thickness of 10-12 meters.

In most cases, krasnozems differ in density and clay composition.They can contain up to 12% humus, but phosphorus is not enough to form a large crop. The characteristics of the red lands can vary greatly, but they all quickly lose their properties after the start of agricultural processing.

Zholtozems

They are typical for the subtropics with a humid and warm climate, based on a thin layer of weathered bark of 2-3 meters. Soils are clayey or loamy.

There is little humus in such soils, on average, 4-5%, in some places - up to 10%. It has a compacted lumpy structure and a grayish tint. Nitrogen here is up to 0.4%, and in the underlying horizons, the amount of humus and nitrogen is significantly reduced.

Zholtozems have lower physical characteristics than red soils.

Yellow soils are divided into the following varieties:

1. Gley.
2. Podzolic yellow soils.
3. Podzolic yellow earth gley.

Such soils have low acidity.

Brown soils

Such soils occur when there is a long summer with high temperatures and dryness, and a short winter without severe frosts. They are characteristic of subtropical areas with carbonate soils, often located at the foot of mountain ranges, contain a significant amount of iron and magnesium, which affects the color. They are also distinguished by the presence of clay, alkaline and slightly alkaline reaction.

Humus in the ground is 2-7%, it is rapidly lost due to leaching after plowing the land. Brown soils have a granular structure with lumps, grow vineyards and melons on them when irrigated.

Grey-brown soils

This variety is typical for the dry steppes of the subtropics, as well as plains, foothills and low mountain areas. Gray-brown soils are a transitional stage from desert gray soils to brown soils. They form in subtropical climates with long, dry summers and short, wet winters.

The humus layer here does not exceed 4.5%, alkaline or slightly alkaline reaction, the earth is lumpy.

You can grow grapes, cotton, subtropical fruit plants such as pomegranate, fig or walnut on gray-brown soils, but only with regular application of mineral fertilizers and established watering.

Black soils

Such soils can be easily confused with chernozems, but, unlike them, black soils contain only 1-2% humus, although the horizon can reach 1 meter. They form on weathered rocks rich in carbonates and iron.

Black soils differ from true chernozems by a significant content of clay particles. Because of this, during the rainy period, the earth strongly absorbs moisture, and when it dries out in the heat and drought, it cracks deeply. The soil reaction can be slightly acidic or slightly alkaline.

Compared to other varieties, black soils are more fertile if mineral fertilizers are applied and irrigation is available.

Sierozems

Gray soils are formed on loess and loess-like loams, which are on pebbles as a substrate. They are porous, loose, permeable, with some clay content.

There is little humus in gray soils, no more than 1-3%, and the layer itself barely reaches 15 centimeters. They have a very high content of carbonates, which causes an alkaline reaction. Such soils are good for agriculture, and regular improvement, fertilization and watering only improve their quality.

Red-yellow earths

The place of formation of such lands is densely overgrown tropical forests. They are found on sedimentary and igneous rocks subject to significant weathering. The change of seasons is hardly noticeable here, the vegetation is formed in a hot and humid climate. The soils are acidic, with a humus content of not more than 4%. They are poorly suited for agriculture, require constant fertilization, but after uprooting trees and plowing, they still quickly lose their useful qualities.

Red ferralite soils

Such soils are typical for savannas with high herbage, variable forests with a dry season of up to 4 months. They contain a lot of iron, which causes their characteristic color and are similar in properties to red-yellow earths, but differ from them in that they dry out to a considerable depth during drought.

Soils of this type are suitable for growing crops, but require liming and the addition of phosphate fertilizers.

Red-brown soils

The place of occurrence of such soils is savannas with a drought duration of up to 6 months. Vegetation dies, leaves fall off, but mineralize in the upper layer due to lack of moisture and rapid drying of organic matter.

Soils are characterized by a fairly large humus horizon - up to 20-30 centimeters, but the humus itself in it is not more than 2%. The reaction of the soil is different, from slightly acidic to slightly alkaline. Contains a high percentage of iron.

Red-brown soils

Their habitat is mountainous areas, formed on rocks subject to strong weathering with a loose structure - loess, loam and clay. The color is due to the influence of iron oxides.

Humus in the ground - up to 3-6%, its amount decreases as it sinks into the horizon. The upper layers give a neutral reaction, but when they occur above carbonate rocks, the reaction becomes alkaline.

These soils grow drought and heat resistant plants.

Applying subtropical and tropical soils

The climate in these zones is excellent for growing a number of crops, especially in need of the conditions characteristic of such areas: high temperatures and an abundance of moisture, both in the soil and in the air.

Although it is believed that local soils have poor fertility, regular application of significant doses of mineral and organic fertilizers can significantly improve it. Oil and essential oil crops, tea, coffee, citrus fruits and many other exotic plants for other areas are cultivated here.

The main problem is water erosion. During the wet season, an abundance of precipitation leads to floods, during which water flows wash away the already meager layer of humus.

Improving agricultural practices and improving fertility can expand the range of plants and increase yields.

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