The 10 main types of soil and their characteristics

Soil is the outermost surface of the Earth, made up of organic matter, minerals, water, and air. This combination of materials is what allows or does not allow the growth of terrestrial plants.

Most of the soil is made up of fragmented and chemically degraded rock that includes sand, silt and clay, and generally contains humus, which is partially decomposed organic matter.

The types of soils are frequently classified by the measure of the mineral particles that make it up. The main types of soils that we can get are:

1. Sandy soils
2. Silty soils
3. Clay soils
4. Loamy soils
5. Calcareous soils
6. Flooded organic soils
7. Urban soils
8. Frozen soils
9. Volcanic soils
10. Stony soils

1. Sandy soils

Sands comprise particles with a diameter of 0.05 mm to 2 mm, mainly quartz minerals. Sandy soils have a higher proportion of sand, compared to silt and clay.

Sandy soils are the most widespread in the world. They occupy a large part of arid and semi-arid regions, from cold to hot climates. The vegetation is mainly herbaceous in deserts, but light forests can also be found.

These soils are characterized by:

• Coarse texture: When the soil is rubbed between the fingers it feels rough and thick.
• High permeability to water: Saturates with little amount of water
• Well aerated: dries quickly in the air.
• Good drainage: they drain easily because they have low water retention capacity.
• It's hard to mold: if it is mixed with a little water and kneaded in the hands, it disintegrates and does not stick.
• Easy to carve: when working with cultivation machines it breaks easily.
• Low availability of water: continuous watering is required for growing plants

Within the sandy soils in the world reference classification of soils are the Arenosols, which include residual sand soils, recently deposited sand soils such as dunes in deserts and Beaches.

2. Silty soils

Silt is composed of particles with diameters between 0.002 mm and 0.05 mm. Silty soils present a proportion of 100 to 80% of silt and have intermediate properties between sandy soils and clay soils.

Silty soils are characterized by:

• Intermediate texture: When you squeeze a little wet silt between your fingers, you can feel it roll up when it dries, leaving the skin clean.
• Silky smooth appearance: when the loamy soil is moistened it is soft, but when it dries it has a dusty appearance.
• Little moldable: when manipulated in the hands it is not sticky and difficult to stretch.
• Moderate water retention: does not retain moisture for long periods of time.
• Water availability: water capacity available to plants

3. Clay soils

Clay is made up of silicates smaller than 2 microns (0.002 mm). Clay soils have a proportion of 100 to 40% clay.

Clay soils are characterized by:

• Fine texture: when rubbed between the fingers the appearance is soft, smooth and as it dries it adheres to the skin.
• Soapy appearance- When excess water is added it feels soapy and slippery.
• Easy to mold: when it is kneaded it can form ribbons and rings.
• High water retention: stores a lot of moisture and takes time to dry.
• Difficult to carve- Being more adhesive, cohesive, sticky and plastic than silt, clay soils are more difficult to work with with agricultural machines.
• Poor drainage: clay soils have a high moisture retention capacity.

4. Loamy soils

Loam soil is a combination of sand, silt and clay in proportions such that it improves the properties of the soil for cultivation. These proportions are achieved in the following ranges: 52-23% sand, 50-32% silt, 27 -7% clay. They are fertile soils and suitable for most crops.

Loamy soils are characterized by:

• Medium texture: when rubbed between the fingers the appearance is lumpy.
• Good water retention: it stores moisture well with which it has a greater availability of water for plants.
• Easy to carve: the combination of sand and clay in loamy soils allows tillage with agricultural machines.
• Good drainage: water does not puddle in loamy soils, but neither does it run off as fast as it does in sandy soils.

5. Calcareous soils

Calcareous soils contain calcium carbonate above 15%. We find them in arid areas of the earth. They correspond to Calcisols in the world reference classification of soils

Calcareous soils are light brown in color where calcium carbonates accumulate within 100 cm of the soil surface. They are formed from alluvial, colluvial and aeolian deposits of base-rich calcareous rocks.

They can be found on flat to mountainous lands in arid and semi-arid environments. Natural vegetation is sparse and dominated by xerophilous trees and shrubs and / or ephemeral grasses and grasses. They are used for extensive grazing.

6. Flooded organic soils

Flooded organic soils are soils formed by the accumulation of organic plant material partially decomposed, with or without a mixture of sand, silt and clay, of little agricultural importance. In the world reference classification of soils they are known as Histosols, from the Greek histos, which means "tissue".

We find these soils in poorly drained basins and depressions, such as swamps and peat bogs, in mangroves or in cold and humid mountainous areas. They develop from moss peat in arctic, sub-arctic and boreal regions, reed peat, reeds and forest in temperate regions to mangrove peat and swamp forest peat in the tropics damp.

They are widely located in the US, Canada, Western Europe, northern Scandinavia, and the West Siberian Plain.

You may also be interested in seeing Biome types.

7. Urban soils

Urban floors or technosols are those floors with a technical origin. They are dominated by man-made material, hence their name is derived from the Greek technikos, which means "skillfully done".

They are characterized by a large number of artifacts, technical hard material or geomembranes.

Technosols include roads, mines, waste dumps, oil spills, and construction sites that are primarily located in urban and industrial areas.

You may also be interested in seeing Types of pollution.

8. Frozen soils

Frozen soils are mineral soils affected by ice, formed in a permafrost environment. Layers below the surface are permanently frozen. They are also known as Cryosols, from the Greek kryos which means "cold", "ice".

Frozen soils are found in flat and mountainous areas in Antarctic, Arctic and boreal regions, associated with tundra regions. The present vegetation is represented by coniferous and lichen forests or mixed deciduous forest.

They are found in a natural state in North America and Eurasia and are used for grazing animals such as caribou, reindeer and musk ox.

9. Volcanic soils

Volcanic soils are dark soils that develop from the expulsion of volcanoes, rich in silicates or glass. In the world reference classification of soils they are called Andosols, which comes from the Japanese an which means "dark" and do, which means "ground".

They are found in any climate, from the arctic to the humid tropical regions, in volcanic regions throughout the world, except in very arid regions.

They are generally fertile soils with a great diversity of vegetation types.

10. Stony soils

Stony soils are soils with very thin or extremely stony continuous rock on the surface. In the world reference classification of soils they are known as Leptosols, from the Greek leptos, which means "slim".

These types of soils are mainly found in mountainous areas, from the tropics to the polar regions. They are used as forest land and for grazing in the rainy season.

You may also be interested in seeing Biotic and abiotic factors

References

Blum, W.E.H., Schad, P., Nortcliff, S. (2018) Essentials of soil science: soil formation, functions, use and classification (World reference base). Borntrager Science Publishers. Stuttgart, Germany.

Eash, N.S., Sauer, T.J., O'Dell, D., Odoi, E. (2016) Soil science simplified 6th ed. Wiley Blackwell. New Jersey.