Soil

Start music   Jan 4 2017 || 11:07 PM

Soil

The mixture of rock particles and humus is called the soil.

 

Formation of Soil

Soil is formed by the breaking down of rocks by the action of wind, water and climate by a process called weathering

 

Soil profile

  • A vertical section through different layers of the soil is called the soil profile
  • If you place a handful of soil in a glass beaker and pour water in it, you can see the layering of soil. It is layered in this order from the top:
    • Humus (The rotting dead matter in the soil)
    • Water
    • Clay
    • Sand
    • Gravel
  • Each layer differs in feel (texture), colour, depth and chemical composition.
  • These layers are referred to as horizons

 

Horizons

A-horizon

  • The uppermost horizon is generally dark in colour as it is rich in humus and minerals
  • It is soft, porous and can retain more water
  • Humans make use of this layer to grow plants and the layer also provides shelter for many organisms (microbes, worms etc)
  • It is called the topsoil or the A-horizon

 

B-horizon

  • The next layer has a lesser amount of humus but more of minerals
  • This layer is generally harder and more compact
  • It is called the B-horizon

 

C-horizon

  • The third layer is made up of small lumps of rocks with cracks and crevices
  • It is called C-horizon

 

Bedrock

  • Below C-horizon lies the bed rock which is hard and difficult to dig through

 

Soil Types

Sandy soil

  • If soil contains greater proportion of big particles
  • They are light, well aerated and water can drain quickly through it (cannot retain much water)

 

Clayey soil

  • If the proportion of fine particles is relatively higher
  • They are much tightly packed, heavier than sandy soil (as they retain more water) and are poorly aerated

 

Loamy soil

  • If the amount of large and fine particles is about the same
  • Silt occurs along with the big and small particles and they are medium sized
  • Can retain the right amount of water and are the best top soil for growing plants

 

Factors responsible for soil characters

  • Rainfall
  • Temperature
  • Light
  • Humidity

 

Soil–Crop Suitability

  • Cereals - Clayey and loamy soils, as they are good at holding water
  • Wheat – Fine clayey soils, because they are rich in humus and are very fertile
  • PaddyClayey soil rich in organic matter & having a good capacity to retain water
  • Lentils and other pulses – Loamy soils, which drain water easily
  • CottonSandy-loam or loam, which drains water easily and can hold plenty of air

 

Soil erosion

  • The removal of land surface by water, wind or ice is known as erosion
  • Erosion of soil is more severe in areas of little or no surface vegetation

 

Soil Distribution in INDIA