- Books Name
- CBSE Class 7 Science Book
- Param Publication
- CBSE Class 7
(i) A vertical section through different layers of the soil is called soil profile.
(ii) Each layer of soil profile differ in colour, depth, chemical composition. These layers are called “soil horizons”.
• Soil profile can be seen in recently dug ditch, during digging a well or laying the foundation of a building.
• Soil profile shows three main horizons : -
A-Horizon: - Uppermost, dark coloured, rich in humus and supports plants and many living organisms like worms, rodents, moles and beetles. Humus makes the soil fertile & provides nutrients to the growing plants. This layer is generally soft, porous and can retain more water. It is also called top soil.
B-Horizon: - It is also called middle layer, which is generally harder and more compact, having less
amount of humus but more minerals.
C-Horizon: - It is made up of small lumps of rocks with cracks & crevices, called third layer. Below this is bed-rock, which is hard and difficult to dig with a spade.
• Soil profile can be observed by dissolving little soil in glass tumbler, three quarters filled with water. Each layer in glass shows different size of soil particles.
• The rotting dead matter in the soil is called humus.