What Is Soil

An estimated 70 percent of the earth’s surface is covered with water, while the remaining 30 per cent constitutes land. The layer of the earth that is composed of soil and is influenced by the process of soil formation is called pedosphere. But what exactly is soil and what is soil made of?

What is Soil?

Technically, the soil is a mixture that contains minerals, organic matter, and living organisms. But broadly speaking, soil can refer to any loose sediment. Moreover, there are many types of soil that are distributed around the world and these are generally classified into the following:

  1. Clay Soil
  2. Sandy soil
  3. Loamy Soil
  4. Silt Soil

Typically, the soil consists of 45% minerals, 50% empty spaces or voids and 5% organic matter. Furthermore, soil performs many important functions such as:

  1. Providing a growth medium for the plants
  2. Acts a modifier of the earth’s atmosphere
  3. One of the most crucial components of the biosphere
  4. Provides habitat for organisms

Also Read: Soil Teeming

How is Soil Formed?

Soil is formed by weathering of rocks. Solid rock can weather away in one of the three ways into the soil, namely:

  1. Mechanical Weathering
  2. Chemical Weathering
  3. Biological Weathering

Mechanical Weathering

This is commonly observed near the surface of the earth. Also called physical weathering, as this process is influenced by physical forces such as wind, water and temperature.

Chemical Weathering

As the name suggests, chemical weathering occurs when rocks are broken down by chemical reactions. Often, such types of weathering can change the chemical composition of the soil.

Biological Weathering

Though not an actual weathering process, living organisms weaken and subsequently disintegrate rocks, often by initiating mechanical or chemical weathering. For instance, tree roots can grow into cracks in the rock, prying them apart and causing mechanical fractures. Microorganisms can secrete chemicals that can increase the rock’s susceptibility to weathering.

Also Read: Soil Profile

Composition of Soil

The soil is composed of different components: 5% organic matter, 45% minerals, 20-30% different gases and 20-30% water. Therefore, the soil is known as a heterogeneous body. Given below is the composition of soil in detail:

Organic Matter

Organic substance is found in very small amounts in the soil. Plants and animals are the main sources of organic matter. Depending upon the decomposition stage, the organic matter is of the following three types:

  • Completely decomposed organic matter
  • Partially decomposed organic matter
  • Undecomposed organic matter


Minerals are an important element of the soil. These are solid components composed of atoms. These occur naturally and have a fixed chemical composition. Olivine and feldspar are the main minerals present in the soil.

Gaseous Components

The air-filled pores of the soil contain the gaseous components. Nitrogen and oxygen present in the pores is generally the atmospheric air fixed by the microorganisms. However, the composition of carbon dioxide is higher due to the gas produced by microorganisms present in the soil.


The soil dissolves the minerals and nutrients in the water and transports it to different parts of the plants. These are essential for the growth and development of the plant.

Importance of Soil

Soil is an important element essential for the survival of living organisms. The importance of soil is mentioned below:

  1. The fertile soil helps in the growth and development of the plants. The plants thus produced are healthy and provide food, clothing, furniture, and medicines.
  2. It supports many life forms including bacteria, fungi, algae, etc. These microbes, in turn, maintain environmental balance by retaining the moisture and decaying the dead organisms.
  3. The topsoil supports certain life activities such as reproduction, hatching, nesting, breeding, etc. of a few organisms.
  4. The organic matter present in the soil increases the fertility of the soil which is responsible for the growth of the plants. It also contains certain minerals and elements that are necessary for the plants to carry out their cellular activities.
  5. Soil is used for making cups, utensils, tiles, etc. The contents in the soil such as gravel, clay and sand are used in the construction of homes, roads, buildings, etc.
  6. Useful mineral medicines such as calcium, iron, and other substances such as petroleum jelly for cosmetics are extracted from the soil.
  7. The soil absorbs the rainwater. This water is evaporated and released into the air during sunny days, making the atmosphere cooler.

Also Read: Mineral Riches In The Soil

Thus we see how the soil is formed, what it is composed of and how it is important to different life forms.

To know more about soil, its formation, composition and importance (along with other important concepts such as soil pollution), download BYJU’S – The Learning App.

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