The 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 not the growth of terrestrial plants.
Most soil is made up of fragmented and chemically weathered rock including sand, silt, and clay, and generally contains humus, which is partially decomposed organic matter.
The types of soils are frequently classified by the size of the mineral particles that make them up. The main types of floors that we can get are:
Sandy soils Silty soils Clay soils Loamy soils Calcareous soils Flooded organic soils Urban soils Frozen soils Volcanic soils Stony soils
1. Sandy soils
The sands comprise particles with a diameter of 0.05 mm to 2 mm, mainly of 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 much of the arid and semi-arid regions, from cold to hot climates. The vegetation is mainly herbaceous in the deserts, but light forests can also be found.
These soils are characterized by:
coarse texture: when the soil is rubbed between your fingers it feels rough and thick.
High water permeability: Saturates with a small amount of water
well aerated: dries quickly in the air.
good drainage: they drain easily because they have a low water retention capacity.
It’s hard to shape: if it is mixed with a little water and kneaded in the hands, it disintegrates and does not stick.
easy to till: when working with cultivation machines it breaks easily.
Low water availability: for the cultivation of the plants continuous watering is required
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 beach lands.
2. Silty soils
Silt is composed of particles with diameters between 0.002 mm and 0.05 mm. Silty soils have a proportion of 100 to 80% silt and have intermediate properties between sandy soils and clayey soils.
Silty soils are characterized by:
intermediate texture: When you squeeze a bit of wet slime between your fingers, you can feel it curl up as it dries, leaving the skin clean.
Smooth and silky appearance: When moist, silty soil is soft, but when it dries it has a powdery appearance.
Little moldable: when handling it 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: capacity of water available to plants
3. Clay soils
Clay is made up of silicates smaller than 2 micrometers (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 shape: when kneaded it can form ribbons and rings.
High water retention: Stores a lot of moisture and takes time to dry.
hard to till: being more adhesive, cohesive, sticky and plastic than silt, clayey soils are more difficult to work with agricultural machines.
poor drainage: Clay soils have a high moisture retention capacity.
4. Loam soils
Loam soil is a combination of sand, silt and clay in such proportions 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.
Loam soils are characterized by:
medium texture: when rubbed between fingers the appearance is lumpy.
good water retention: stores moisture well with which it has a greater availability of water for plants.
easy to till: the combination of sand and clay in loamy soils allows tilling with agricultural machines.
good drainage: water does not pool in loamy soils, but neither does it run off as fast as 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 calcareous rocks rich in bases.
They can be found on flat to mountainous lands in arid and semi-arid environments. The natural vegetation is sparse and dominated by xerophytic trees and shrubs and/or grasses and ephemeral herbs. They are used for extensive grazing.
6. Flooded organic soils
Flooded organic soils are soils formed by the accumulation of organic material from partially decomposed plants, 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 historieswhich means “fabric”.
We find these soils in poorly drained basins and depressions, such as swamps and peat bogs, in mangrove swamps, or in cool, humid montaneous areas. They develop from peat moss in arctic, sub arctic and boreal regions, reed, reed and forest peat in temperate regions to mangrove peat and swamp forest peat in the humid tropics.
They are widely found in the US, Canada, Western Europe, northern Scandinavia, and the West Siberian Plain.
You may also be interested in seeing Types of biomes.
7. Urban soils
Urban soils or technosols are those soils with a technical origin. They are dominated by man-made material, hence their name is derived from the Greek technicianswhich means “skillfully made”.
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 in urban and industrial areas.
You may also be interested in seeing Types of contamination.
8. Frozen soils
Frozen soils are mineral soils affected by ice, formed in a permafrost environment. The layers below the surface freeze permanently. 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 naturally in North America and Eurasia and are used for grazing by animals such as caribou, reindeer, and musk ox.
9. Volcanic soils
Volcanic soils are dark soils that are developed by 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 still which means “dark” and dowhich means “ground”.
They are found in any climate, from the arctic to humid tropical regions, in volcanic regions all over the world, except in very arid regions.
They are generally fertile soils with a great diversity of types of vegetation.
10. Stony soils
Stony soils are soils with continuous rock that is very thin or extremely stony on the surface. In the world reference classification of soils they are known as Leptosols, from the Greek leptos, which means “thin”.
These types of soils are found mainly 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, Types of rocks.
References
Blum, WEH, Schad, P., Nortcliff, S. (2018) Essentials of soil science: soil formation, functions, use and classification (World reference base). Borntrager Science Publishers. Stuttgart, Germany.
Eash, NS, Sauer, TJ, O’Dell, D., Odoi, E. (2016) Soil science simplified 6th ed. Wiley Blackwell. New Jersey.