Theory:

In the previous topic, we studied the distinct layers of soil and how they were formed. In this topic, we see about the features about the distinct soil layers.
Soil profile
A vertical section of the earth's surface through which distinct soil layers are classified called a soil profile.
 
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This soil profile layers are split into different horizons as below:
 
A-Horizon:
  • It is the topmost layer of soil; hence it is called as topsoil.
  • It is visible to us, usually dark in colour due to its minerals and humus. Humus is the dark brown coloured layer which consists of dead, rotting remains of plants and animals.
  • Topsoil is the most fertile layer of the soil. It gives the plants nutrients, since most plants and roots are confined within this layer.
  • The A-Horizon has a soft texture, porous and can easily retain water, which is why plants' roots grow in the topsoil region.
  • The topsoil is a natural habitat to many living organisms like bacteria, fungi, ants etc.
B-Horizon:
  • It is also called as subsoil.
  • This second or middle layer of soil lies just below the topsoil.
  • It consists of small lumps of rocks.
  • It is lighter in colour than that of topsoil. It does not contain much humus. So, subsoil layer is less fertile than topsoil and contains few living organisms, but subsoil has rich minerals such as iron, aluminium oxides, and calcium carbonate. It is more rigid and compact than the topsoil.
C-Horizon:
  • The layer of soil which lies below the subsoil is called C-Horizon.
  • This third layer of soil is also known as Substratum.
  • It composed of small pieces of broken rocks with cracks and crevices, formed by the weathering of bedrock and parent rock.
  • This layer is more rigid and more compact than the subsoil.
Bedrock:
  • The lowermost layer of the soil is termed as bedrock.
  • Bedrock are those rock pieces which are rich in minerals but contains no humus.
  • It is an unweathered solid rock that is not exposed to climatic conditions like winds or rain.
  • This layer is very hard and is tough to dig with a spade.