Page 113 - SST Class 08

a long period of time. A layer of soil of 1 cm Parent Rock (C-Horizon)
thickness can take 500 or more years to be Below the subsoil is the parent rock or substratum.
formed.
It consists of weathered rock material. It has very
Plants and Animals less humus.

Dead plants and animals contribute to formation Bedrock (D-Horizon)
of humus in the soil.
This layer lies below the parent rock. It is a layer
Soil formation is an extremely slow process. of solid weathered rocks.
which takes place over millions of years. Thus, if
Soils of India
the topsoil is washed away, it will take a very long
time to replace it. Due to varied relief, rocks, climate and natural
vegetation, India has a great variety of soils. The
Parent Rock Plant and Animals colour of the soils, their mineral composition,
Soil
Climate Relief or Topography texture, structure and organic content vary from
place to place. In India, soil may be broadly
Time divided into six types :
Factors of soil formation
Alluvial Soil
Layers of Soil
This type of soil formed by the fine silt and sand
Different layers of soil are called as soil profile . brought down and deposited by the rivers. It is
Each soil profile is divided into a series of layers very fertile and is mainly found in plains along the
called horizons . rivers Ganga and Brahmaputra, in the deltas of

Topsoil (A-Horizon) peninsular India and along the eastern coast. It is
very good to grow paddy, wheat, sugar cane,
This is the uppermost layer of the soil. Humus and
pulses, oilseeds etc. This soil supports nearly half
the finer particles of rock form this layer and of the Indian population. It is classified as khadar
contains most of the nutrients required by plants. or younger alluvium and bangar or older
Humus makes this layer porous and fertile.
alluvium .
F ind Outind Out
Subsoil (B-Horizon)
Subsoil is below the topsoil. It is mostly made up of Find out why do plains support more people unlike
small rock particles and some nutrients such as
mountains or deserts.
soluble minerals and iron oxides. Water collects in
this layer due to which a large amount of minerals Black Soil
is washed out. This process is called leaching . This type of soil is formed by the weathering of
volcanic rocks and lava flows. It is mainly found
Horizon A
Topsoil with in the Deccan region of Maharashtra, parts of
humus Madhya Pradesh and Gujarat. It is very good to
contains most
of the nutrients grow cotton and sugar cane as it is clayey and can
required by retain moisture for a long period.
plants.
Horizon B Red Soil
Subsoil
(sand, silt This type of soil is formed by the weathering of
and clay)
igneous and metamorphic rocks in peninsular
Horizon C
Parent India. Its red colour is due to high iron content. It
rock cannot retain much moisture. It is mainly found
Horizon D
Bedrock around the black soil zone in the Western Ghats,
eastern Madhya Pradesh and in the parts of
Layers of the soil
Land, Soil and Water Resources
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