A-horizon is also known as topsoil. This layer is basically porous, soft, and also can retain water. It contains the maximum water and minerals among other soil profiles. The soil profile is composed of a series of horizons or layers of soil stacked one on top of the other. These layers or horizons are represented by letters O, A, E, C, B and R.
The O horizon is the upper layer of the topsoil which is mainly composed of organic materials such as dried leaves, grasses, dead leaves, small rocks, twigs, surface organisms, fallen trees, and other decomposed organic matter. This horizon of soil is often black brown or dark brown in colour and this is mainly because of the presence of organic content.
The A-Horizon or Topsoil
This layer is rich in organic material and is known as the humus layer. This layer consists of both organic matter and other decomposed materials. The topsoil is soft and porous to hold enough air and water.
This layer is composed of nutrients leached from the O and A horizon. This layer is more common in forested areas and has lower clay content.
The B-Horizon or Subsoil
It is the subsurface horizon, present just below the topsoil and above the bedrock. This layer holds enough water than the topsoil and is lighter brown due to the presence of clay soil.
The C-Horizon or Saprolite
This layer is devoid of any organic matter and is made up of broken bedrock. This layer is also known as saprolite. The geological material present in this zone is cemented.
It is a compacted and cemented layer. Different types of rocks such as granite, basalt and limestone are found here.