NCERT Textbook - Soils | Geography (Prelims) by Valor Academy - UPSC PDF Download

 Page 1


H
ave you ever thought about the most
important factor which supports trees,
grasses, crops and numerous life-
forms over the earth’s surface?  Can one grow
a blade of grass without soil? While some
plants and organisms which are aquatic in
nature can sustain in water , do they not derive
nutrients from soil through water?  You will
realise  that  soil is the most important layer of
the earth’s crust. It is a valuable resource. The
bulk of our food and much of our clothing is
derived from land-based crops that grow in the
soil. The soil on which we depend so much for
our day-to-day needs has evolved over
thousands of years. The various agents of
weathering and gradation have acted upon the
parent rock material to produce a thin layer of
soil.
Soil is the mixture of rock debris and
organic materials which develop on the earth’s
surface. The major factors affecting the
formation of soil are relief, parent material,
climate, vegetation and other life-forms and
time. Besides these, human activities also
influence it to a large extent. Components of
the soil are mineral particles, humus, water and
air. The actual amount of each of these depend
upon the type of soil. Some soils are deficient
in one or more of these, while there are some
others that have varied combinations.
Have you ever dug a pit in the field of your
school to plant a tree while celebrating Van-
Mahotsava? Was the pit of uniform layer of soil
or did you notice different colours from the top
to the bottom of the pit?
If we dig a pit on land and look at the soil,
we find that it consists of three layers which
are called horizons. ‘Horizon A’ is the topmost
zone, where organic materials have got
incorporated with the mineral matter ,
nutrients and water, which are necessary for
the growth of plants. ‘Horizon B’ is a transition
zone between the ‘horizon A’ and ‘horizon C’,
and contains matter derived from below as well
as from above. It has some organic matter in
it, although the mineral matter is noticeably
weathered. ‘Horizon C’ is composed of the loose
parent material. This layer is the first stage in
the soil formation process and eventually forms
the above two layers. This arrangement of layers
is known as the soil profile. Underneath these
three horizons is the rock which is also known
as the parent rock or the bedrock. Soil, which
is a complex and varied entity has always
drawn the attention of the scientists.  In order
to understand its importance, it is essential to
attempt a scientific study of the soil.
Classification of the soil is an effort to achieve
this objective.
CLASSIFICATION OF SOILS
India has varied relief features, landforms,
climatic realms and vegetation types.  These
have contributed in the development of various
types of soils in India.
In ancient times, soils used to be classified
into two main groups – Urvara and Usara,
which were fertile and sterile, respectively. In
the 16th centrury A.D., soils were classified on
the basis of their inherent characteristics and
external features such as texture, colour , slope
of land and moisture content in the soil. Based
on texture, main soil types were identified as
SOILS
CHAPTER
2022-23
Page 2


H
ave you ever thought about the most
important factor which supports trees,
grasses, crops and numerous life-
forms over the earth’s surface?  Can one grow
a blade of grass without soil? While some
plants and organisms which are aquatic in
nature can sustain in water , do they not derive
nutrients from soil through water?  You will
realise  that  soil is the most important layer of
the earth’s crust. It is a valuable resource. The
bulk of our food and much of our clothing is
derived from land-based crops that grow in the
soil. The soil on which we depend so much for
our day-to-day needs has evolved over
thousands of years. The various agents of
weathering and gradation have acted upon the
parent rock material to produce a thin layer of
soil.
Soil is the mixture of rock debris and
organic materials which develop on the earth’s
surface. The major factors affecting the
formation of soil are relief, parent material,
climate, vegetation and other life-forms and
time. Besides these, human activities also
influence it to a large extent. Components of
the soil are mineral particles, humus, water and
air. The actual amount of each of these depend
upon the type of soil. Some soils are deficient
in one or more of these, while there are some
others that have varied combinations.
Have you ever dug a pit in the field of your
school to plant a tree while celebrating Van-
Mahotsava? Was the pit of uniform layer of soil
or did you notice different colours from the top
to the bottom of the pit?
If we dig a pit on land and look at the soil,
we find that it consists of three layers which
are called horizons. ‘Horizon A’ is the topmost
zone, where organic materials have got
incorporated with the mineral matter ,
nutrients and water, which are necessary for
the growth of plants. ‘Horizon B’ is a transition
zone between the ‘horizon A’ and ‘horizon C’,
and contains matter derived from below as well
as from above. It has some organic matter in
it, although the mineral matter is noticeably
weathered. ‘Horizon C’ is composed of the loose
parent material. This layer is the first stage in
the soil formation process and eventually forms
the above two layers. This arrangement of layers
is known as the soil profile. Underneath these
three horizons is the rock which is also known
as the parent rock or the bedrock. Soil, which
is a complex and varied entity has always
drawn the attention of the scientists.  In order
to understand its importance, it is essential to
attempt a scientific study of the soil.
Classification of the soil is an effort to achieve
this objective.
CLASSIFICATION OF SOILS
India has varied relief features, landforms,
climatic realms and vegetation types.  These
have contributed in the development of various
types of soils in India.
In ancient times, soils used to be classified
into two main groups – Urvara and Usara,
which were fertile and sterile, respectively. In
the 16th centrury A.D., soils were classified on
the basis of their inherent characteristics and
external features such as texture, colour , slope
of land and moisture content in the soil. Based
on texture, main soil types were identified as
SOILS
CHAPTER
2022-23
69 SOILS
sandy, clayey, silty and loam, etc. On the basis
of colour, they were red, yellow, black, etc.
Since Independence, scientific surveys of
soils have been conducted by various agencies.
Soil Survey of India, established in 1956, made
comprehensive studies of soils in selected areas
like in the Damodar Valley. The National
Bureau of Soil Survey and the Land Use
Planning an Institute under the control of the
Indian Council of Agricultural Research (ICAR)
did a lot of studies on Indian soils. In their effort
to study soil and to make it comparable at the
international level, the ICAR has classified the
Indian soils on the basis of their nature and
character as per the United States Department
of Agriculture (USDA) Soil Taxonomy.
ICAR has classified the soils of India into the
following order as per the USDA soil taxonomy
Sl. Order Area Percentage
No. (in Thousand
Hectares)
(i) Inceptisols 130372.90 39.74
(ii) Entisols 92131.71 28.08
(iii) Alfisols 44448.68 13.55
(iv) Vertisols 27960.00 8.52
(v) Aridisols 14069.00 4.28
(vi) Ultisols 8250.00 2.51
(vi) Mollisols 1320.00 0.40
(viii) Others 9503.10 2.92
Total 100
Source : Soils of India, National Bureau of Soil
Survey and Land Use Planning, Publication
Number 94
On the basis of genesis, colour ,
composition and location, the soils of India
have been classified into:
(i) Alluvial soils
(ii) Black soils
(iii) Red and Yellow soils
(iv) Laterite soils
(v) Arid soils
(vi) Saline soils
(vii) Peaty soils
(viii) Forest soils.
Alluvial Soils
Alluvial soils are widespread in the northern
plains and the river valleys.  These soils cover
about 40 per cent of the total area of the
country. They are depositional soils,
transported and deposited by rivers and
streams. Through a narrow corridor in
Rajasthan, they extend into the plains of
Gujarat. In the Peninsular region, they are
found in deltas of the east coast and in the river
valleys.
 The alluvial soils vary in nature from sandy
loam to clay. They are generally rich in potash
but poor in phosphorous. In the Upper and
Middle Ganga plain, two different types of
alluvial soils have developed, viz. Khadar and
Bhangar. Khadar is the new alluvium and is
deposited by floods annually, which enriches
the soil by depositing fine silts. Bhangar
represents a system of older alluvium,
deposited away from the flood plains. Both the
Khadar and Bhangar soils contain calcareous
concretions (Kankars).  These soils are more
loamy and clayey in the lower and middle
Ganga plain and the Brahamaputra valley. The
sand content decreases from the west to east.
The colour of the alluvial soils varies from
the light grey to ash grey. Its shades depend
on the depth of the deposition, the texture of
the materials, and the time taken for attaining
maturity. Alluvial soils are intensively
cultivated.
Black Soil
Black soil covers most of the Deccan Plateau
which includes parts of Maharashtra, Madhya
Pradesh, Gujarat, Andhra Pradesh and some
parts of Tamil Nadu. In the upper reaches of
the Godavari and the Krishna, and the north
Figure 6.1 : Alluvial Soil
2022-23
Page 3


H
ave you ever thought about the most
important factor which supports trees,
grasses, crops and numerous life-
forms over the earth’s surface?  Can one grow
a blade of grass without soil? While some
plants and organisms which are aquatic in
nature can sustain in water , do they not derive
nutrients from soil through water?  You will
realise  that  soil is the most important layer of
the earth’s crust. It is a valuable resource. The
bulk of our food and much of our clothing is
derived from land-based crops that grow in the
soil. The soil on which we depend so much for
our day-to-day needs has evolved over
thousands of years. The various agents of
weathering and gradation have acted upon the
parent rock material to produce a thin layer of
soil.
Soil is the mixture of rock debris and
organic materials which develop on the earth’s
surface. The major factors affecting the
formation of soil are relief, parent material,
climate, vegetation and other life-forms and
time. Besides these, human activities also
influence it to a large extent. Components of
the soil are mineral particles, humus, water and
air. The actual amount of each of these depend
upon the type of soil. Some soils are deficient
in one or more of these, while there are some
others that have varied combinations.
Have you ever dug a pit in the field of your
school to plant a tree while celebrating Van-
Mahotsava? Was the pit of uniform layer of soil
or did you notice different colours from the top
to the bottom of the pit?
If we dig a pit on land and look at the soil,
we find that it consists of three layers which
are called horizons. ‘Horizon A’ is the topmost
zone, where organic materials have got
incorporated with the mineral matter ,
nutrients and water, which are necessary for
the growth of plants. ‘Horizon B’ is a transition
zone between the ‘horizon A’ and ‘horizon C’,
and contains matter derived from below as well
as from above. It has some organic matter in
it, although the mineral matter is noticeably
weathered. ‘Horizon C’ is composed of the loose
parent material. This layer is the first stage in
the soil formation process and eventually forms
the above two layers. This arrangement of layers
is known as the soil profile. Underneath these
three horizons is the rock which is also known
as the parent rock or the bedrock. Soil, which
is a complex and varied entity has always
drawn the attention of the scientists.  In order
to understand its importance, it is essential to
attempt a scientific study of the soil.
Classification of the soil is an effort to achieve
this objective.
CLASSIFICATION OF SOILS
India has varied relief features, landforms,
climatic realms and vegetation types.  These
have contributed in the development of various
types of soils in India.
In ancient times, soils used to be classified
into two main groups – Urvara and Usara,
which were fertile and sterile, respectively. In
the 16th centrury A.D., soils were classified on
the basis of their inherent characteristics and
external features such as texture, colour , slope
of land and moisture content in the soil. Based
on texture, main soil types were identified as
SOILS
CHAPTER
2022-23
69 SOILS
sandy, clayey, silty and loam, etc. On the basis
of colour, they were red, yellow, black, etc.
Since Independence, scientific surveys of
soils have been conducted by various agencies.
Soil Survey of India, established in 1956, made
comprehensive studies of soils in selected areas
like in the Damodar Valley. The National
Bureau of Soil Survey and the Land Use
Planning an Institute under the control of the
Indian Council of Agricultural Research (ICAR)
did a lot of studies on Indian soils. In their effort
to study soil and to make it comparable at the
international level, the ICAR has classified the
Indian soils on the basis of their nature and
character as per the United States Department
of Agriculture (USDA) Soil Taxonomy.
ICAR has classified the soils of India into the
following order as per the USDA soil taxonomy
Sl. Order Area Percentage
No. (in Thousand
Hectares)
(i) Inceptisols 130372.90 39.74
(ii) Entisols 92131.71 28.08
(iii) Alfisols 44448.68 13.55
(iv) Vertisols 27960.00 8.52
(v) Aridisols 14069.00 4.28
(vi) Ultisols 8250.00 2.51
(vi) Mollisols 1320.00 0.40
(viii) Others 9503.10 2.92
Total 100
Source : Soils of India, National Bureau of Soil
Survey and Land Use Planning, Publication
Number 94
On the basis of genesis, colour ,
composition and location, the soils of India
have been classified into:
(i) Alluvial soils
(ii) Black soils
(iii) Red and Yellow soils
(iv) Laterite soils
(v) Arid soils
(vi) Saline soils
(vii) Peaty soils
(viii) Forest soils.
Alluvial Soils
Alluvial soils are widespread in the northern
plains and the river valleys.  These soils cover
about 40 per cent of the total area of the
country. They are depositional soils,
transported and deposited by rivers and
streams. Through a narrow corridor in
Rajasthan, they extend into the plains of
Gujarat. In the Peninsular region, they are
found in deltas of the east coast and in the river
valleys.
 The alluvial soils vary in nature from sandy
loam to clay. They are generally rich in potash
but poor in phosphorous. In the Upper and
Middle Ganga plain, two different types of
alluvial soils have developed, viz. Khadar and
Bhangar. Khadar is the new alluvium and is
deposited by floods annually, which enriches
the soil by depositing fine silts. Bhangar
represents a system of older alluvium,
deposited away from the flood plains. Both the
Khadar and Bhangar soils contain calcareous
concretions (Kankars).  These soils are more
loamy and clayey in the lower and middle
Ganga plain and the Brahamaputra valley. The
sand content decreases from the west to east.
The colour of the alluvial soils varies from
the light grey to ash grey. Its shades depend
on the depth of the deposition, the texture of
the materials, and the time taken for attaining
maturity. Alluvial soils are intensively
cultivated.
Black Soil
Black soil covers most of the Deccan Plateau
which includes parts of Maharashtra, Madhya
Pradesh, Gujarat, Andhra Pradesh and some
parts of Tamil Nadu. In the upper reaches of
the Godavari and the Krishna, and the north
Figure 6.1 : Alluvial Soil
2022-23
70 INDIA : PHYSICAL ENVIRONMENT
Figure 6.2 : Major Soil Types of India
2022-23
Page 4


H
ave you ever thought about the most
important factor which supports trees,
grasses, crops and numerous life-
forms over the earth’s surface?  Can one grow
a blade of grass without soil? While some
plants and organisms which are aquatic in
nature can sustain in water , do they not derive
nutrients from soil through water?  You will
realise  that  soil is the most important layer of
the earth’s crust. It is a valuable resource. The
bulk of our food and much of our clothing is
derived from land-based crops that grow in the
soil. The soil on which we depend so much for
our day-to-day needs has evolved over
thousands of years. The various agents of
weathering and gradation have acted upon the
parent rock material to produce a thin layer of
soil.
Soil is the mixture of rock debris and
organic materials which develop on the earth’s
surface. The major factors affecting the
formation of soil are relief, parent material,
climate, vegetation and other life-forms and
time. Besides these, human activities also
influence it to a large extent. Components of
the soil are mineral particles, humus, water and
air. The actual amount of each of these depend
upon the type of soil. Some soils are deficient
in one or more of these, while there are some
others that have varied combinations.
Have you ever dug a pit in the field of your
school to plant a tree while celebrating Van-
Mahotsava? Was the pit of uniform layer of soil
or did you notice different colours from the top
to the bottom of the pit?
If we dig a pit on land and look at the soil,
we find that it consists of three layers which
are called horizons. ‘Horizon A’ is the topmost
zone, where organic materials have got
incorporated with the mineral matter ,
nutrients and water, which are necessary for
the growth of plants. ‘Horizon B’ is a transition
zone between the ‘horizon A’ and ‘horizon C’,
and contains matter derived from below as well
as from above. It has some organic matter in
it, although the mineral matter is noticeably
weathered. ‘Horizon C’ is composed of the loose
parent material. This layer is the first stage in
the soil formation process and eventually forms
the above two layers. This arrangement of layers
is known as the soil profile. Underneath these
three horizons is the rock which is also known
as the parent rock or the bedrock. Soil, which
is a complex and varied entity has always
drawn the attention of the scientists.  In order
to understand its importance, it is essential to
attempt a scientific study of the soil.
Classification of the soil is an effort to achieve
this objective.
CLASSIFICATION OF SOILS
India has varied relief features, landforms,
climatic realms and vegetation types.  These
have contributed in the development of various
types of soils in India.
In ancient times, soils used to be classified
into two main groups – Urvara and Usara,
which were fertile and sterile, respectively. In
the 16th centrury A.D., soils were classified on
the basis of their inherent characteristics and
external features such as texture, colour , slope
of land and moisture content in the soil. Based
on texture, main soil types were identified as
SOILS
CHAPTER
2022-23
69 SOILS
sandy, clayey, silty and loam, etc. On the basis
of colour, they were red, yellow, black, etc.
Since Independence, scientific surveys of
soils have been conducted by various agencies.
Soil Survey of India, established in 1956, made
comprehensive studies of soils in selected areas
like in the Damodar Valley. The National
Bureau of Soil Survey and the Land Use
Planning an Institute under the control of the
Indian Council of Agricultural Research (ICAR)
did a lot of studies on Indian soils. In their effort
to study soil and to make it comparable at the
international level, the ICAR has classified the
Indian soils on the basis of their nature and
character as per the United States Department
of Agriculture (USDA) Soil Taxonomy.
ICAR has classified the soils of India into the
following order as per the USDA soil taxonomy
Sl. Order Area Percentage
No. (in Thousand
Hectares)
(i) Inceptisols 130372.90 39.74
(ii) Entisols 92131.71 28.08
(iii) Alfisols 44448.68 13.55
(iv) Vertisols 27960.00 8.52
(v) Aridisols 14069.00 4.28
(vi) Ultisols 8250.00 2.51
(vi) Mollisols 1320.00 0.40
(viii) Others 9503.10 2.92
Total 100
Source : Soils of India, National Bureau of Soil
Survey and Land Use Planning, Publication
Number 94
On the basis of genesis, colour ,
composition and location, the soils of India
have been classified into:
(i) Alluvial soils
(ii) Black soils
(iii) Red and Yellow soils
(iv) Laterite soils
(v) Arid soils
(vi) Saline soils
(vii) Peaty soils
(viii) Forest soils.
Alluvial Soils
Alluvial soils are widespread in the northern
plains and the river valleys.  These soils cover
about 40 per cent of the total area of the
country. They are depositional soils,
transported and deposited by rivers and
streams. Through a narrow corridor in
Rajasthan, they extend into the plains of
Gujarat. In the Peninsular region, they are
found in deltas of the east coast and in the river
valleys.
 The alluvial soils vary in nature from sandy
loam to clay. They are generally rich in potash
but poor in phosphorous. In the Upper and
Middle Ganga plain, two different types of
alluvial soils have developed, viz. Khadar and
Bhangar. Khadar is the new alluvium and is
deposited by floods annually, which enriches
the soil by depositing fine silts. Bhangar
represents a system of older alluvium,
deposited away from the flood plains. Both the
Khadar and Bhangar soils contain calcareous
concretions (Kankars).  These soils are more
loamy and clayey in the lower and middle
Ganga plain and the Brahamaputra valley. The
sand content decreases from the west to east.
The colour of the alluvial soils varies from
the light grey to ash grey. Its shades depend
on the depth of the deposition, the texture of
the materials, and the time taken for attaining
maturity. Alluvial soils are intensively
cultivated.
Black Soil
Black soil covers most of the Deccan Plateau
which includes parts of Maharashtra, Madhya
Pradesh, Gujarat, Andhra Pradesh and some
parts of Tamil Nadu. In the upper reaches of
the Godavari and the Krishna, and the north
Figure 6.1 : Alluvial Soil
2022-23
70 INDIA : PHYSICAL ENVIRONMENT
Figure 6.2 : Major Soil Types of India
2022-23
71 SOILS
western part of the Deccan Plateau, the black
soil is very deep. These soils are also known as
the ‘Regur Soil’ or  the ‘Black Cotton Soil’. The
black soils are generally clayey, deep and
impermeable. They swell and become sticky
when wet and shrink when dried.  So, during
the dry season, these soil develop wide cracks.
Thus, there occurs a kind of ‘self ploughing’.
Because of this character of slow absorption
and loss of moisture, the black soil retains the
moisture for a very long time, which helps the
crops, especially, the rain fed ones, to sustain
even during the dry season.
Chemically, the black soils are rich in lime,
iron, magnesia and alumina. They also contain
potash. But they lack in phosphorous,
nitrogen and organic matter. The colour of the
soil ranges from deep black to grey.
Red and Yellow Soil
Red soil develops on crystalline igneous rocks
in areas of low rainfall in the eastern and
southern part of the Deccan Plateau. Along the
piedmont zone of the W estern Ghat, long stretch
of area is occupied by red loamy soil. Y ellow and
red soils are also found in parts of Odisha and
Chhattisgarh and in the southern parts of the
middle Ganga plain. The soil develops a reddish
colour due to a wide diffusion of iron in crystalline
and metamorphic rocks. It looks yellow when it
occurs in a hydrated form. The fine-grained red
and yellow soils are normally fertile, whereas
coarse-grained soils found in dry upland areas
are poor in fertility. They are generally poor in
nitrogen, phosphorous and humus.
Laterite Soil
Laterite has been derived from the Latin word
‘Later’ which means brick. The laterite soils
develop in areas with high temperature and
high rainfall.  These are the result of intense
leaching due to tropical rains. With rain, lime
and silica are leached away, and soils rich in
iron oxide and aluminium compound are left
behind. Humus content of the soil is removed
fast by bacteria that thrives well in high
temperature. These soils are poor in organic
matter, nitrogen, phosphate and calcium,
while iron oxide and potash are in excess.
Hence, laterites are not suitable for cultivation;
however, application of manures and fertilisers
are required for making the soils fertile for
cultivation.
Red laterite soils in Tamil Nadu, Andhra
Pradesh and Kerala are more suitable for tree
crops like cashewnut.
Laterite soils are widely cut as bricks for
use in house construction. These soils have
mainly developed in the higher areas of the
Peninsular plateau. The laterite soils are
commonly found in Karnataka, Kerala, Tamil
Nadu, Madhya Pradesh and the hilly areas of
Odisha and Assam.
Arid Soils
Arid soils range from red to brown in colour.
They are generally sandy in structure and
saline in nature. In some areas, the salt content
is so high that common salt is obtained by
evaporating the saline water. Due to the dry
climate, high temperature and accelerated
evaporation, they lack moisture and humus.
Nitrogen is insufficient and the phosphate
Figure 6.3 : Black Soil During Dry Season
Figure 6.4 : Arid Soil
2022-23
Page 5


H
ave you ever thought about the most
important factor which supports trees,
grasses, crops and numerous life-
forms over the earth’s surface?  Can one grow
a blade of grass without soil? While some
plants and organisms which are aquatic in
nature can sustain in water , do they not derive
nutrients from soil through water?  You will
realise  that  soil is the most important layer of
the earth’s crust. It is a valuable resource. The
bulk of our food and much of our clothing is
derived from land-based crops that grow in the
soil. The soil on which we depend so much for
our day-to-day needs has evolved over
thousands of years. The various agents of
weathering and gradation have acted upon the
parent rock material to produce a thin layer of
soil.
Soil is the mixture of rock debris and
organic materials which develop on the earth’s
surface. The major factors affecting the
formation of soil are relief, parent material,
climate, vegetation and other life-forms and
time. Besides these, human activities also
influence it to a large extent. Components of
the soil are mineral particles, humus, water and
air. The actual amount of each of these depend
upon the type of soil. Some soils are deficient
in one or more of these, while there are some
others that have varied combinations.
Have you ever dug a pit in the field of your
school to plant a tree while celebrating Van-
Mahotsava? Was the pit of uniform layer of soil
or did you notice different colours from the top
to the bottom of the pit?
If we dig a pit on land and look at the soil,
we find that it consists of three layers which
are called horizons. ‘Horizon A’ is the topmost
zone, where organic materials have got
incorporated with the mineral matter ,
nutrients and water, which are necessary for
the growth of plants. ‘Horizon B’ is a transition
zone between the ‘horizon A’ and ‘horizon C’,
and contains matter derived from below as well
as from above. It has some organic matter in
it, although the mineral matter is noticeably
weathered. ‘Horizon C’ is composed of the loose
parent material. This layer is the first stage in
the soil formation process and eventually forms
the above two layers. This arrangement of layers
is known as the soil profile. Underneath these
three horizons is the rock which is also known
as the parent rock or the bedrock. Soil, which
is a complex and varied entity has always
drawn the attention of the scientists.  In order
to understand its importance, it is essential to
attempt a scientific study of the soil.
Classification of the soil is an effort to achieve
this objective.
CLASSIFICATION OF SOILS
India has varied relief features, landforms,
climatic realms and vegetation types.  These
have contributed in the development of various
types of soils in India.
In ancient times, soils used to be classified
into two main groups – Urvara and Usara,
which were fertile and sterile, respectively. In
the 16th centrury A.D., soils were classified on
the basis of their inherent characteristics and
external features such as texture, colour , slope
of land and moisture content in the soil. Based
on texture, main soil types were identified as
SOILS
CHAPTER
2022-23
69 SOILS
sandy, clayey, silty and loam, etc. On the basis
of colour, they were red, yellow, black, etc.
Since Independence, scientific surveys of
soils have been conducted by various agencies.
Soil Survey of India, established in 1956, made
comprehensive studies of soils in selected areas
like in the Damodar Valley. The National
Bureau of Soil Survey and the Land Use
Planning an Institute under the control of the
Indian Council of Agricultural Research (ICAR)
did a lot of studies on Indian soils. In their effort
to study soil and to make it comparable at the
international level, the ICAR has classified the
Indian soils on the basis of their nature and
character as per the United States Department
of Agriculture (USDA) Soil Taxonomy.
ICAR has classified the soils of India into the
following order as per the USDA soil taxonomy
Sl. Order Area Percentage
No. (in Thousand
Hectares)
(i) Inceptisols 130372.90 39.74
(ii) Entisols 92131.71 28.08
(iii) Alfisols 44448.68 13.55
(iv) Vertisols 27960.00 8.52
(v) Aridisols 14069.00 4.28
(vi) Ultisols 8250.00 2.51
(vi) Mollisols 1320.00 0.40
(viii) Others 9503.10 2.92
Total 100
Source : Soils of India, National Bureau of Soil
Survey and Land Use Planning, Publication
Number 94
On the basis of genesis, colour ,
composition and location, the soils of India
have been classified into:
(i) Alluvial soils
(ii) Black soils
(iii) Red and Yellow soils
(iv) Laterite soils
(v) Arid soils
(vi) Saline soils
(vii) Peaty soils
(viii) Forest soils.
Alluvial Soils
Alluvial soils are widespread in the northern
plains and the river valleys.  These soils cover
about 40 per cent of the total area of the
country. They are depositional soils,
transported and deposited by rivers and
streams. Through a narrow corridor in
Rajasthan, they extend into the plains of
Gujarat. In the Peninsular region, they are
found in deltas of the east coast and in the river
valleys.
 The alluvial soils vary in nature from sandy
loam to clay. They are generally rich in potash
but poor in phosphorous. In the Upper and
Middle Ganga plain, two different types of
alluvial soils have developed, viz. Khadar and
Bhangar. Khadar is the new alluvium and is
deposited by floods annually, which enriches
the soil by depositing fine silts. Bhangar
represents a system of older alluvium,
deposited away from the flood plains. Both the
Khadar and Bhangar soils contain calcareous
concretions (Kankars).  These soils are more
loamy and clayey in the lower and middle
Ganga plain and the Brahamaputra valley. The
sand content decreases from the west to east.
The colour of the alluvial soils varies from
the light grey to ash grey. Its shades depend
on the depth of the deposition, the texture of
the materials, and the time taken for attaining
maturity. Alluvial soils are intensively
cultivated.
Black Soil
Black soil covers most of the Deccan Plateau
which includes parts of Maharashtra, Madhya
Pradesh, Gujarat, Andhra Pradesh and some
parts of Tamil Nadu. In the upper reaches of
the Godavari and the Krishna, and the north
Figure 6.1 : Alluvial Soil
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70 INDIA : PHYSICAL ENVIRONMENT
Figure 6.2 : Major Soil Types of India
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71 SOILS
western part of the Deccan Plateau, the black
soil is very deep. These soils are also known as
the ‘Regur Soil’ or  the ‘Black Cotton Soil’. The
black soils are generally clayey, deep and
impermeable. They swell and become sticky
when wet and shrink when dried.  So, during
the dry season, these soil develop wide cracks.
Thus, there occurs a kind of ‘self ploughing’.
Because of this character of slow absorption
and loss of moisture, the black soil retains the
moisture for a very long time, which helps the
crops, especially, the rain fed ones, to sustain
even during the dry season.
Chemically, the black soils are rich in lime,
iron, magnesia and alumina. They also contain
potash. But they lack in phosphorous,
nitrogen and organic matter. The colour of the
soil ranges from deep black to grey.
Red and Yellow Soil
Red soil develops on crystalline igneous rocks
in areas of low rainfall in the eastern and
southern part of the Deccan Plateau. Along the
piedmont zone of the W estern Ghat, long stretch
of area is occupied by red loamy soil. Y ellow and
red soils are also found in parts of Odisha and
Chhattisgarh and in the southern parts of the
middle Ganga plain. The soil develops a reddish
colour due to a wide diffusion of iron in crystalline
and metamorphic rocks. It looks yellow when it
occurs in a hydrated form. The fine-grained red
and yellow soils are normally fertile, whereas
coarse-grained soils found in dry upland areas
are poor in fertility. They are generally poor in
nitrogen, phosphorous and humus.
Laterite Soil
Laterite has been derived from the Latin word
‘Later’ which means brick. The laterite soils
develop in areas with high temperature and
high rainfall.  These are the result of intense
leaching due to tropical rains. With rain, lime
and silica are leached away, and soils rich in
iron oxide and aluminium compound are left
behind. Humus content of the soil is removed
fast by bacteria that thrives well in high
temperature. These soils are poor in organic
matter, nitrogen, phosphate and calcium,
while iron oxide and potash are in excess.
Hence, laterites are not suitable for cultivation;
however, application of manures and fertilisers
are required for making the soils fertile for
cultivation.
Red laterite soils in Tamil Nadu, Andhra
Pradesh and Kerala are more suitable for tree
crops like cashewnut.
Laterite soils are widely cut as bricks for
use in house construction. These soils have
mainly developed in the higher areas of the
Peninsular plateau. The laterite soils are
commonly found in Karnataka, Kerala, Tamil
Nadu, Madhya Pradesh and the hilly areas of
Odisha and Assam.
Arid Soils
Arid soils range from red to brown in colour.
They are generally sandy in structure and
saline in nature. In some areas, the salt content
is so high that common salt is obtained by
evaporating the saline water. Due to the dry
climate, high temperature and accelerated
evaporation, they lack moisture and humus.
Nitrogen is insufficient and the phosphate
Figure 6.3 : Black Soil During Dry Season
Figure 6.4 : Arid Soil
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72 INDIA : PHYSICAL ENVIRONMENT
content is normal. Lower horizons of the soil
are occupied by ‘kankar’ layers because of the
increasing calcium content downwards. The
‘Kankar’ layer formation in the bottom horizons
restricts the infiltration of water, and as such
when irrigation is made available, the soil
moisture is readily available for a sustainable
plant growth. Arid soils are characteristically
developed in western Rajasthan, which exhibit
characteristic arid topography. These soils are
poor and contain little humus and organic
matter.
Saline Soils
They are also known as Usara soils. Saline soils
contain a larger proportion of sodium,
potassium and magnesium, and thus, they are
infertile, and do not support any vegetative
growth. They have more salts, largely because
of dry climate and poor drainage. They occur
in arid and semi-arid regions, and in
waterlogged and swampy areas. Their
structure ranges from sandy to loamy. They
lack in nitrogen and calcium. Saline soils are
more widespread in western Gujarat, deltas of
the eastern coast and in Sunderban areas of
West Bengal. In the Rann of Kuchchh, the
Southwest Monsoon brings salt particles and
deposits there as a crust. Seawater intrusions
in the deltas promote the occurrence of saline
soils. In the areas of intensive cultivation with
excessive use of irrigation, especially in areas
of green revolution, the fertile alluvial soils are
becoming saline. Excessive irrigation with dry
climatic conditions promotes capillary action,
which results in the deposition of salt on the
top layer of the soil. In such areas, especially
in Punjab and Haryana, farmers are advised
to add gypsum to solve the problem of salinity
in the soil.
Peaty Soils
They are found in the areas of heavy rainfall
and high humidity, where there is a good
growth of vegetation. Thus, large quantity of
dead organic matter accumulates in these
areas, and this gives a rich humus and organic
content to the soil.  Organic matter in these
soils may go even up to 40-50 per cent. These
soils are normally heavy and black in colour.
At many places, they are alkaline also. It occurs
widely in the northern part of Bihar, southern
part of Uttarakhand and the coastal areas of
West Bengal, Odisha and Tamil Nadu.
Forest Soils
As the name suggests, forest soils are formed in
the forest areas where sufficient rainfall is
available. The soils vary in structure and texture
depending on the mountain environment where
they are formed. They are loamy and silty on
valley sides and coarse-grained in the upper
slopes. In the snow-bound areas of the
Himalayas, they experience denudation, and
are acidic with low humus content. The soils
found in the lower valleys are fertile.
It is evident from the foregoing discussions
that soils, their texture, quality and nature are
vital for the germination and growth of plant
and vegetation including crops. Soils are living
systems.  Like any other organism, they too
develop and decay, get degraded, respond to
proper treatment if administered in time. These
have serious repercussions on other
components of the system of which they
themselves are important parts.
SOIL DEGRADATION
In a broad sense, soil degradation can be
defined as the decline in soil fertility, when the
nutritional status declines and depth of the soil
goes down due to erosion and misuse. Soil
degradation is the main factor leading to the
depleting soil resource base in India.  The degree
of soil degradation varies from  place to place
according to the topography, wind velocity and
amount of the rainfall.
SOIL EROSION
The destruction of the soil cover is described as
soil erosion. The soil forming processes and the
erosional processes of running water and wind
go on simultaneously.  But generally, there is a
balance between these two processes.  The rate
of removal of fine particles from the surface is
the same as the rate of addition of particles to
the soil layer.
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