SOIL
ICSE GEOGRAPHY

What is soil?
Soil is the uppermost thin layer of small rock
particles and organic matter that covers
Earth’s surface on which all life depends as a
source of food directly or indirectly.
Soil is the medium in which plants grow and
thus it supports the lives on earth.

Definition
Soil essentially is the loose material
which forms the thin layer of the
Earth.

Formation of soil
• Forces of nature affect formation of soil
• Temperature, running water, wind along with
chemical and organic changes contribute to
evolution of soil.
• Denudation and disintegration of rocks result in
formation of soil.
• The process of soil formation is called
pedogenesis.

Factors which determine soil
formation
• Climatic conditions
• Topography
• Weathering of rocks and erosion

• Minerals-Silica, clay, chalk
• Organic matter-Humus
• Water
• Air
Composition of soil

Humus
• Humus is formed by the
decomposition(decay)of plant remains,
dead animals and animal manures.
• It is an organic matter and essential
element in determining the fertility of
the soil.
• It is an important part of the soil.

Layers of soil
• Top soil : Most important layer of the soil
since it contains humus. It contains all kinds
of bacteria, worms, insects and decayed plant
life.
• Subsoil : Layer beneath the top soil. It
consists of parent material which are further
reduced to form soil. Moisture and minerals
are present but no humus.

Types of soil found in India
• Alluvial soil
• Black soil
• Red soil
• Laterite soil
• Desert soil
• Mountain soil

Soils of India

ALLUVIAL SOIL
They are depositional soils - transported and deposited
by rivers and streams. These soils are formed by the
deposition of fine sediments and silt by the rivers
along their banks.
The major rivers which help in the formation of the
alluvial soils are :
• The Ganga and its tributaries - Yamuna, Gomti,
Gandak, Ghaghara, Kosi etc.
• The Brahmaputra river.
• The Indus and its tributaries - Jhelum, Chenab, Sutlej,
Ravi, Beas
• River Narmada, Mahanadi , Godavari, Krishna etc.

Characteristics
• Found at depth of 500
metres.
• Yellow in color.
• Soil is rich in potash,
humus and lime.
• Texture varies from
coarse to fine.
• Poor in nitrogen and
humus.
• Tends to be phosphoric.
• Suitable for growing
paddy, sugarcane, wheat,
cotton, oil seeds, etc.

Two types of Alluvial soils (basis of
origin)
Khadar
1. These are found in the
lower areas of deltas, lower
beds of the plains through
which river meanders and
beds of valley bottom
which are flooded almost
every year.
2. It is non porous, clayey and
loamy.
3. It consist of new alluvium.
Bhangar
1.They are found 30m above
flood level of the rivers.
2.These consist of older
alluvium of clayey
composition and are dark
in colour.
3.They are coarse in nature;
contain kankar, pebbles,
and gravels.

Two types of Alluvial soils
• Inland Alluvium
These soils occur in the
large plains of North
India by Himalayan
rivers, Ganga river,
Sutlej, Brahmaputra
river and their
tributaries.
• Deltaic Alluvium
They get darker as
rivers flow over the
black soil.
Deltaic alluvium
occurs in the deltas of
Mahanadi, Godavari,
Krishna and Kaveri
rivers.

Crops grown
Suitable for growing paddy,
sugarcane, wheat, cotton, oil seeds,
tobacco, gram, etc.

Areas: Lower Ganga Brahmaputra valley
Coastal strip of Peninsular India
States: Punjab, Haryana, Uttar Pradesh,
Orissa, Tamil Nadu etc.
Areas where Alluvial soils are found

BLACK SOIL
• Also known as Regur soil.
• Dark grey to Black in color. Why?
• The soil is black in color because it is
volcanic in origin.

Formation
• Black soils are of volcanic origin.
• Lava soil are formed due to
disintegration of basalt rocks and often
referred to as regur soils.

Black soil is called black cotton soil
because cotton thrives well on it.
Cotton is the most common crop
cultivated on it.
Black Cotton soil

In situ
Found at their area of
origin/formation, over
the underlying rocks.
Spread over Deccan
Plateau as a result of
Volcanic activity.
Example: black soil
Ex situ
Soils transported by
rivers.
Example: alluvial soil

• Deep fine grained and varying in color - black to chestnut
brown.
• Rich in iron, lime, calcium, magnesium, carbonates, and
alumina.
• Have high clay content.
• Highly moist retentive, very sticky when wet. Forms deep
cracks when dry.
• Highly suitable for cotton.
• Deficient in phosphate, nitrogen and humus or organic matter.
Characteristics

Crops grown
Cotton, sugarcane, groundnuts, millets,
rice, wheat, oilseeds like linseed and
sunflower and fruits, grams etc.

Areas where Black soils are found
•Deccan Trap which includes: Maharashtra,
greater part of Gujarat, M.P
•Parts of western A.P, Karnataka, Parts of
Tamil Nadu and Rajasthan.

RED SOIL
Red soils are reddish in color due to
the presence of iron oxide content .
They look yellow when in the
hydrated form

Formation
• Formed due to weathering of old
crystalline and metamorphic rocks. It is a
mixture of sand and clay.
• It is mostly found in low rainfall areas.

Characteristics
• Red in color due to the
presence of iron.
varying in color
chocolate brown to
yellow.
• Rich in iron, small
amount of Humus.
• Rich in potash.
• Slightly acidic and not
moisture retentive.
• Poor in phosphorus,
nitrogen and lime.
• Porous and friable.

Crops grown
Rice, wheat, sugarcane, ragi, groundnut, millet,
tobacco etc.
With application of proper fertilizers and
irrigation they give excellent yield.

Areas where Red soils are found
Areas: Plateau regions of peninsular India, the
Malwa plateau, Chhota Nagpur plateau
States: Tamil Nadu, Southern Karnataka, parts of
Madhya Pradesh, Maharashtra,West Bengal,
Chhattisgarh, Odisha, Eastern Rajasthan, North
Eastern states.

LATERITE SOIL
• Formed by leaching of laterite rocks under
high temperature and heavy rainfall with
alternating dry and wet periods.
• Laterite soil formation takes place under
monsoon conditions.

Is red due to the presence of iron oxide which is
formed by leaching.
Is a porous soil, silica is removed from it by
chemical action.
Is poor in lime and magnesium and deficient in
nitrogen.
High content of acidity and inability to retain
moisture.
Is of coarse texture, soft and friable.
Characteristics

What is leaching?
• Laterite soils are found in elevated areas which
receive very high rainfall. As a result, the top
soil gets washed away. This process is called
leaching.
• Leaching is a process in which the (soluble)
nutrients get percolated down below the soil
due to heavy rainfall; thus leaving the top soil
infertile, also called DESILICATION.

Why unsuitable for cultivation?
Silica and lime are leached due to high rainfall leaves
behind a poor soil which is unsuitable for cultivation.
Because of high acidity and low moisture retention
fertility is low.
Manuring and other activities are required to make
them suitable for growing crops such as ragi, rice and
sugarcane.
Suitable for plantations
As these soils are rich in iron - are suitable for
plantation of crops like tea, rubber, coffee etc.

Crops grown
Cashew and tapioca are grown on laterite soil
Soils are highly acidic and poor to retain moisture
Laterite soils are suitable for plantations crops like
tea, coffee, rubber, coconut

Areas where Laterite soils are found
Areas: Summits of Eastern Ghats and Western
Ghats and hilly regions of Assam, Rajmahal
hills and Chhota Nagpur plateau
States: Andhra Pradesh, Tamil Nadu,
Karnataka, Kerala

Soil is formed slowly and is destroyed easily. It is
upper most thin layer of the Earth’s crust. Soil
serves as reservoir of minerals, organic, inorganic
and nutrient constituents.
It is indispensable(essential) medium for the
growth and development of plants.
Why should we conserve soil?

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