What is soil?

Ksenia Vilinskaya
Ksenia Vilinskaya
February 2, 2015
What is soil?

The soil is the upper crust with a loose structure. The soil was formed under the influence of water, the processes occurring in the atmosphere, the vital activity of plants, animals and microorganisms. It has a mineral base - about 60 percent of the total. Organic matter is much less - about 10 percent. The soil also contains air (up to 25 percent) and water (up to 30-35 percent). Let us consider in more detail what the soil consists of.

Soil composition

The mineral base of the soil is as follows:

  • sand;
  • aleurite;
  • clay minerals.

The organic component of the soil is humus. This substance is formed from the remains of plants and animals. Decomposition occurs under the action of saprophytes - organisms that feed on inanimate substance (earthworms, for example). In swampy soils, humus is formed very slowly; it is part of the peat, which also consists of not completely decomposed remains of plants and animals and contains a lot of water.

Air and water are trapped inside the soil. Part of the water goes outside - these waters are called groundwater.

Soil horizons (soil types)

If you mentally “cut” the soil in depth, you will get a vertical cut with visible layers that are different in color and composition. This cut is called the soil profile, and the layers forming it are the soil horizons. Some horizons have sub-horizons. Latin letters are used to designate them.

A - the uppermost horizon. Organic matter accumulates here. The layer consists of humus.

The humus layer has the following sub-horizons:

  • Ao is a layer characteristic of forest areas. It is formed by forest litter - needles, leaves, etc. Hell is turf. Here the weave of root systems of grasses growing on the surface are expressed with the soil.
  • A1- humus-eluvial subhorizon. On marshy soils, respectively, instead of humus horizon (A) - peat (T).
  • A2 - this eluvial horizon. The processes of destruction and leaching of mineral substances occur in it. The color of the layer is light.

Depending on the specific processes occurring in it, it happens:

  • podzolic horizon (peculiar to forests, formed due to acid hydrolysis of minerals, with acidic soil);
  • solodilous horizon (characteristic of forest-steppes, steppes; formed by alkaline hydrolysis);
  • gley-eluvial (found most often in wetlands).

Under the upper horizons is the horizon B, the illuvial, where the products of the destruction of minerals fall. Iron can be deposited in these layers, calcium inclusions can occur. Chernozems do not have an eluvial horizon, which makes B a transitional layer - from humus to the parent rock.

There are also horizons G - gley, C - rock, or D - bedrock.

You have learned what soil is.