The genesis of soils UPSC |मिट्टी की उत्पत्ति| Biogeography| Physical Geography


  • The thin or thick layer of grainy substances/loose materials which cover the earth's surface is called soil.
  • Soil contains organic matter[humus and microorganism] from the biosphere, minerals from the lithosphere, water[hydrosphere], and air[ atmosphere] in various proportions.
  • These elements serve as nutrients to plants and serve as a medium for growing organisms.
  • The right mixup of minerals, organic matter, air, and water makes the soil fertile.
  • Soil thrives on plants as well as organisms such as rodents, worms, insects, snacks, and microorganisms such as fungi, bacteria, and algae.
The average composition of soil contains:
  • 45 % Mineral
  • 5 % Organic matters
  • 50 % of water and air
Soil Genesis:
The transformation of rocks into agricultural land is called "soil formation" or Soil genesis.
Soil genesis starts from the weathering process of the parent rock. Weathered materials undergo many chemical and biological changes under different climatic conditions.

The following five factors and five processes are involved in the soil genesis process.
Five Factors are:
  • Parent Rock
  • Climatic Factors
  • Relief
  • Flora, Fauna, and Micro Organism
  • Time
Five Processes are:
  • Lateralization and bacterization
  • Calcification
  • Salinization
  • Podzolization
  • Gleization

Parent Rock:

  • Parent rock may be Igneous, Metamorphic, or sedimentary rock.
  • It determines the color, texture, chemical properties, and minerals of the soil.
  • Soil gets sand, silt, and clay from parent rock.
  • For examples
    • Black soil is made up of weathered materials of Basaltic volcanoes Rock.
    • Red soil is made up of Igneous rock.

Climatic Factors:

  • Major climate attributes such as precipitation, temperature affect the soil formation process.
  • For example,
    • Desert soil developed through the calcification process under high temperatures and very low precipitation.
    • Semi-arid developed through the calcification process[ when evaporation is greater than precipitation] under capillary action.
    • Peaty soil developed through the Gleization process under cool and humid conditions[ waterlogging areas].
    • In the Podozolization process, Fe and Al move downward and acidic soil forms.
    • Laterite soils developed under equatorial climatic conditions having heavy precipitation and.


  • Altitudes and slopes also determine the thickness or thinness of the soil. Plain areas are coved with thick soil whereas steep terrain has thin soils.

Flora, fauna, and micro organism: 

  • Determine the rate of humus formation.
  • There is sufficient humus in the forest areas because of the abundance of flora, fauna, and microorganism whereas desert areas lack humus.
  • Humus content in the soils also lacking in the laterite soils because of the presence of microorganisms.


  • Time determines the thickness of the soil profile.
The following are five processes involved in the soil genesis after the weathering process:
Lateralization and bacterization: 
  • This process commonly happens in hot wet tropical and equatorial climates. 
  • Due to high temperature and heavy rainfall, the bacterization process increase leads to less humus content in the upper part of the soil.
  • Heavy rainfall leads to the leaching of dissolved minerals from the upper layer to the B "layer" of the soil profile.
  • Hence, in the Laterite soil; the B layer of soil is rich in minerals.
  • Laterite soil is more suitable for bigger trees.
  • The calcification process happens in the Savana types of climate[ temperature around 35 degrees centigrade and 75 cm precipitation].
  • Soil nutrients came upon the earth's surface from a lower profile and make it suitable for grass vegetation and unsuitable for trees.
  • The salinization process commonly happens in hot desert areas where precipitation is very low and the temperature is very high.
  • Extreme evaporation brings the underground salts to the surface. 
  • This is also happening in irrigated areas of low rainfall areas.
  • For example, in some areas of Punjab and Rajasthan. 
  • This occurred in a cool and humid climate where bacteria activity is low. In this region, the thick dark organic surface having organic compounds can be translocated by heavy rainfall. 
  • Podzolization process happens in Taiga Forest, Coniferous soil, and Boreal forest

  • This process took in waterlogged and anaerobic conditions. Some specialized bacteria flourish that use organic matter, this leads to a reduction of iron and aluminum compounds and makes the soil more acidic.
  • For example, 
    • Peaty soil, and Marshy Soil.
    • It is extensively found in the UK

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