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Factors Affecting Soil Formation

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Soil - a natural resource - definition

  • The soil is an important part of the landscape and contributes to determine the way in which natural vegetation, crops and human settlements are distributed on the territory.
  • Soil is the mixture of minerals, organic matter, gases, liquids, and the countless organisms that together support life on Earth.

Uses of soil - definition

Soil plays a vital role in the survival of living beings on the earth. Its importance can be listed as
  • Soil fertility: Fertile soil supports growth of plants.
  • Soil microbiology: It provides support for survival of many bacteria, algae, fungi etc. These bacteria and microbes present in soil help in environmental balance like retaining of moisture, decay of dead bodies of animals, plants etc.
  • Top soil provides shelter for insects, reptiles, birds and animals. Further top soil is necessary for even other activities like nesting, reproduction, hatching of eggs, breeding etc.
  • Soil organic matter contains essential minerals and elements like phosphates, sulphates, calcium, zinc, magnesium and many more. These elements are provided to plant during growth and from there to all the living forms.
  • Soil a source of minerals: Minerals and mines present in soil is the source of many metals like iron, bauxite, zinc etc. Many metal elements are mixed up with soil and hence extracted from soil by technical processes.

Formation of soil - definition

  • The process of soil formation is known as weathering.
  • Weathering is the process of disintegration of parent rocks into smaller particles (regolith). The weathering basis of agents can be classified as

    (a) Physical weathering

    (b) Chemical weathering

    (c) Biological weathering

  • Physical weathering: The physical agents responsible for such weathering are temperature, wind, water, ice, gravity, etc.
  • Chemical weathering: When different chemical processes are involved in weathering it is known as chemical weathering. The important chemical weathering agents are moisture, water and air. 
  • The chemical processes involved in chemical weathering are:

    (1) Hydration, (2) Hydrolysis, (3) Oxidation, (4) Reduction, (5) Carbonation

  • Biological weathering: Various types of microorganisms extract minerals from rocks as their energy source.
  • This ultimately leads to change in the physical structures and mineral
    composition of the rocks.

Constituents of soil - definition

  • A soil is simply a porous medium consisting of minerals, water, gases, organic matter, and microorganisms.
There are five basic components of soil- 
  • 1. Mineral - The largest component of soil is the mineral portion, which makes up approximately 45% to 49% of the volume.
  • 2. Water - Water is the second basic component of soil. Water can make up approximately 2% to 50% of the soil volume.
  • 3. Organic matter - Organic matter is the next basic component that is found in soils at levels of approximately 1% to 5%.
  • 4. Gases - Gases or air is the next basic component of soil. Because air can occupy the same spaces as water, it can make up approximately 2% to 50% of the soil volume.
  • 5. Microorganisms - Microorganisms are the final basic element of soils, and they are found in the soil in very high numbers but make up much less than 1% of the soil volume.

Related Concepts

Soil Erosion and Its Prevention