Indian Soils

Soil is a mixture of rock debris and organic materials that develops on the Earth’s surface.

It is not just loose earth.

It is a living natural body formed through a long process involving rocks, climate, organisms, vegetation, relief and time.

Soil supports agriculture, vegetation, forests, water storage and life on land.

In India, soils vary from region to region because the country has different landforms, climates, rocks, rainfall conditions, vegetation types and drainage systems.

What Is Soil?

Soil is made up of weathered rock material, organic matter, air and water.

It forms on the surface of the Earth when rocks break down and mix with decayed plant and animal matter.

Soil is important because it provides:

• Nutrients for plants.
• Water for crop growth.
• Air for root respiration.
• Support for vegetation.
• Base for agriculture.

Factors Affecting Soil Formation

The major factors that affect soil formation are:

• Parent material.
• Relief.
• Climate.
• Vegetation.
• Other life forms.
• Time.
• Human activities.

Each factor plays a different role.

For example, parent rock decides the mineral content of soil, rainfall affects leaching, vegetation adds humus, and time allows soil layers to develop.

Elements Of Soil

In general, soil is composed of four main elements:

• Inorganic or mineral fractions derived from parent material.
• Organic matter from decayed and decomposed plants and animals.
• Air present in soil pores.
• Water stored between soil particles.

A fertile soil needs a proper balance of these elements.

Pedogenesis

The process of soil formation is called pedogenesis.

Soil forms under specific natural conditions.

Each element of the natural environment contributes to this complex process.

Pedogenesis is slow and continuous.

It may take hundreds or thousands of years to form a mature soil profile.

Soil Profile And Soil Horizons

Soil consists of different layers.

These layers are called horizons.

The arrangement of these horizons is known as the soil profile.

The chapter explains three main horizons:

• Horizon A
• Horizon B
• Horizon C

Horizon A

Horizon A is the topmost zone of soil.

In this layer, organic materials are mixed with mineral matter, nutrients and water.

This layer is very important for plant growth.

It contains:

• Organic matter.
• Mineral particles.
• Nutrients.
• Water.
• Plant roots.

Horizon B

Horizon B is the transition zone between Horizon A and Horizon C.

It contains materials derived from both above and below.

It has some organic matter, but mineral matter is more noticeable.

The material in this layer is usually more weathered.

Horizon C

Horizon C is made of loose parent material.

It represents the first stage in the soil formation process.

Over time, this parent material helps form the upper soil horizons.

Soil Profile At A Glance

Horizon	Main Feature
Horizon A	Topsoil, organic matter, nutrients and water
Horizon B	Transition zone with weathered mineral matter
Horizon C	Loose parent material

Classification Of Soils In India

In ancient times, Indian soils were broadly classified into two groups:

• Urvara – fertile soil.
• Usara – sterile soil.

Later, modern scientific classification developed with detailed soil surveys.

Soil Survey Of India

The Soil Survey of India was established in 1956.

It carried out comprehensive studies of soils in selected areas such as the Damodar Valley.

ICAR Classification Of Indian Soils

The Indian Council of Agricultural Research, or ICAR, studied Indian soils and classified them according to their nature and character.

ICAR classified Indian soils on the basis of the United States Department of Agriculture, or USDA Soil Taxonomy.

ICAR Soil Orders In India

Soil Order	Area in Thousand Hectares	Percentage
Inceptisols	130372.90	39.74
Entisols	92131.71	28.08
Alfisols	44448.68	13.55
Vertisols	27960.00	8.52
Aridisols	14069.00	4.28
Ultisols	8250.00	2.51
Mollisols	1320.00	0.40
Others	9503.10	2.92

For exams, remember that Inceptisols cover the largest area among ICAR soil orders in India.

Major Soil Types Of India

On the basis of genesis, colour, composition and location, Indian soils are classified into 8 major types:

• Alluvial soils.
• Black soils.
• Red and yellow soils.
• Laterite soils.
• Arid soils.
• Saline soils.
• Peaty soils.
• Forest soils.

1. Alluvial Soils

Alluvial soils are the most widespread and agriculturally important soils of India.

They are mainly found in the northern plains and river valleys.

They cover about 40 per cent of the total area of the country.

Formation Of Alluvial Soils

Alluvial soils are depositional soils.

They are transported and deposited by rivers and streams.

Rivers bring sediments such as sand, silt and clay from mountains and plateaus and deposit them in plains, valleys and deltas.

Distribution Of Alluvial Soils

Alluvial soils are found in:

• Northern plains.
• River valleys.
• A narrow corridor in Rajasthan extending into Gujarat plains.
• Deltas of the east coast.
• River valleys of the Peninsular region.

Texture And Composition

Alluvial soils vary in texture.

They may be:

• Sandy.
• Loamy.
• Clayey.

They are generally rich in potash but poor in phosphorous.

Khadar And Bhangar

Two important types of alluvial soils are:

• Khadar
• Bhangar

Khadar

Khadar is new alluvium.

It is deposited by floods almost every year.

Annual deposition of fine silt enriches the soil and makes it fertile.

Khadar is usually found in flood plains.

Bhangar

Bhangar is older alluvium.

It is deposited away from the active flood plains.

It forms older terraces and is less frequently renewed by floods.

Both Khadar and Bhangar contain calcareous concretions known as Kankars.

Colour Of Alluvial Soils

The colour of alluvial soils varies from light grey to ash grey.

The shade depends on:

• Depth of deposition.
• Texture of materials.
• Time taken for maturity.

Crops Grown In Alluvial Soils

Alluvial soils are highly fertile and intensively cultivated.

They support many crops such as:

• Rice.
• Wheat.
• Maize.
• Soybean.
• Chickpea.
• Sugarcane.
• Cotton.
• Jute.
• Oilseeds.
• Vegetables.
• Fruits.

Important Features Of Alluvial Soil

• Most widespread soil of India.
• Covers about 40 per cent of the country.
• Deposited by rivers and streams.
• Found in northern plains, river valleys and deltas.
• Texture varies from sandy to loamy to clayey.
• Rich in potash.
• Poor in phosphorous.
• Divided into Khadar and Bhangar.
• Highly fertile and intensively cultivated.

2. Black Soil

Black soil is one of the most important soils of Peninsular India.

It is also known as:

• Regur Soil
• Black Cotton Soil

It is especially suitable for cotton cultivation.

Distribution Of Black Soil

Black soil covers most of the Deccan Plateau.

It is found in parts of:

• Maharashtra.
• Madhya Pradesh.
• Gujarat.
• Andhra Pradesh.
• Tamil Nadu.

It is very deep in the upper reaches of the Godavari and Krishna rivers and in the north-western part of the Deccan Plateau.

Physical Properties Of Black Soil

Black soil is:

• Clayey.
• Deep.
• Sticky when wet.
• Hard when dry.
• Rich in moisture-retention capacity.

It swells when wet and shrinks when dry.

During the dry season, it develops wide cracks.

This cracking leads to self-ploughing, as the soil loosens naturally.

Why Black Soil Is Suitable For Cotton

Black soil is ideal for cotton because it retains moisture for a long time.

Cotton needs moisture during its growing period, and black soil helps rain-fed crops survive even in dry conditions.

Chemical Composition Of Black Soil

Black soils are rich in:

• Lime.
• Iron.
• Magnesia.
• Alumina.
• Potash.

They are poor in:

• Phosphorous.
• Nitrogen.
• Organic matter.

Colour Of Black Soil

The colour of black soil ranges from deep black to grey.

Crops Grown In Black Soil

Important crops grown in black soil include:

• Cotton.
• Wheat.
• Jowar.
• Groundnut.
• Sugarcane.
• Soybean.
• Pulses.
• Linseed.
• Sunflower.
• Tobacco.
• Fruits and vegetables.

Important Features Of Black Soil

• Also called Regur soil.
• Also called black cotton soil.
• Found mainly in Deccan Plateau.
• Clayey, deep and moisture-retentive.
• Swells when wet and shrinks when dry.
• Develops cracks in dry season.
• Known as self-ploughed soil.
• Rich in lime, iron, magnesia, alumina and potash.
• Poor in nitrogen, phosphorous and organic matter.
• Best suited for cotton.

3. Red And Yellow Soil

Red and yellow soils are found mainly in parts of the Deccan Plateau and adjoining regions.

They develop on crystalline igneous rocks in areas of low rainfall.

Formation Of Red And Yellow Soil

Red soil develops on crystalline igneous rocks.

It is common in areas of low rainfall in the eastern and southern parts of the Deccan Plateau.

The soil gets its red colour due to the diffusion of iron in crystalline and metamorphic rocks.

It appears yellow when iron occurs in hydrated form.

Distribution Of Red And Yellow Soil

Red and yellow soils are found in:

• Eastern part of the Deccan Plateau.
• Southern part of the Deccan Plateau.
• Piedmont zone of the Western Ghats.
• Parts of Odisha.
• Parts of Chhattisgarh.
• Southern parts of the middle Ganga plain.

A long stretch along the piedmont zone of the Western Ghats is occupied by red loamy soil.

Fertility Of Red And Yellow Soil

Fine-grained red and yellow soils are generally fertile.

Coarse-grained soils in dry upland areas are poor in fertility.

These soils are generally poor in:

• Nitrogen.
• Phosphorous.
• Humus.

Crops Grown In Red And Yellow Soil

With proper irrigation and fertilizers, these soils can support crops such as:

• Wheat.
• Rice.
• Cotton.
• Sugarcane.
• Pulses.
• Millets such as jowar and bajra.
• Oilseeds.
• Potatoes.

Important Features Of Red And Yellow Soil

• Develops on crystalline igneous rocks.
• Common in low rainfall areas.
• Red colour due to iron diffusion.
• Yellow colour due to hydrated iron.
• Fine-grained soils are fertile.
• Coarse-grained upland soils are poor.
• Poor in nitrogen, phosphorous and humus.

4. Laterite Soil

The word Laterite is derived from the Latin word Later, which means brick.

Laterite soils develop in areas of high temperature and high rainfall.

They are formed by intense leaching under tropical rainfall conditions.

Formation Of Laterite Soil

In high rainfall areas, rainwater leaches away lime and silica.

After this leaching, soil rich in iron oxide and aluminium compounds is left behind.

Because of high temperature, bacteria quickly remove humus content from the soil.

Chemical Composition

Laterite soils are poor in:

• Organic matter.
• Nitrogen.
• Phosphate.
• Calcium.

They are rich in:

• Iron oxide.
• Potash.
• Aluminium compounds.

Because of low fertility, laterite soils are generally not suitable for cultivation without improvement.

Manures and fertilizers are needed to make them productive.

Distribution Of Laterite Soil

Laterite soils are commonly found in:

• Karnataka.
• Kerala.
• Tamil Nadu.
• Madhya Pradesh.
• Hilly areas of Odisha.
• Hilly areas of Assam.

Crops Grown In Laterite Soil

Red laterite soils in Tamil Nadu, Andhra Pradesh and Kerala are more suitable for tree crops like:

• Cashew nut.
• Tapioca.

Important Features Of Laterite Soil

• Derived from Latin word Later, meaning brick.
• Develops in high temperature and high rainfall areas.
• Formed due to intense leaching.
• Lime and silica are leached away.
• Rich in iron oxide and aluminium compounds.
• Poor in organic matter, nitrogen, phosphate and calcium.
• Requires manures and fertilizers for cultivation.
• Suitable for cashew nut and tapioca in some regions.

5. Arid Soils

Arid soils are found in dry and desert regions.

They develop under arid climate where rainfall is low and evaporation is high.

Colour And Texture

Arid soils range from red to brown in colour.

They are generally:

• Sandy in structure.
• Saline in nature.
• Poor in moisture.
• Poor in humus.

Chemical Properties

Arid soils are poor in nitrogen.

Their phosphate content is normal.

The lower horizons contain Kankar layers due to increasing calcium content downwards.

Role Of Kankar Layer

The Kankar layer restricts water infiltration.

When irrigation is available, soil moisture becomes available for plant growth because water does not easily drain away.

Distribution Of Arid Soils

Arid soils are characteristically developed in western Rajasthan.

This region has typical arid topography.

Crops Grown In Arid Soil

Crops suitable for arid soils include:

• Pearl millet.
• Sorghum.
• Cotton.
• Chickpeas.
• Cowpeas.

These crops are drought-tolerant and can survive in low moisture conditions.

Important Features Of Arid Soil

• Found in arid and desert regions.
• Red to brown in colour.
• Sandy and saline.
• Lacks moisture and humus.
• Poor in nitrogen.
• Normal phosphate content.
• Lower horizons contain Kankar layers.
• Found mainly in western Rajasthan.

6. Saline Soils

Saline soils are also known as Usara soils.

They contain a large proportion of salts such as sodium, potassium and magnesium.

Because of excess salts, these soils are infertile and do not support normal vegetative growth.

Properties Of Saline Soil

Saline soils contain more:

• Sodium.
• Potassium.
• Magnesium.

They lack:

• Nitrogen.
• Calcium.

Their structure ranges from sandy to loamy.

Distribution Of Saline Soils

Saline soils occur in:

• Arid regions.
• Semi-arid regions.
• Waterlogged areas.
• Swampy areas.
• Western Gujarat.
• Deltas of the eastern coast.
• Sundarban areas of West Bengal.

In the Rann of Kutch, the southwest monsoon brings salt particles and deposits them as a crust.

How Salinity Is Treated

In areas such as Punjab and Haryana, farmers are advised to add gypsum to solve the problem of salinity.

Gypsum helps improve saline soils by reducing the harmful effect of excess sodium.

Crops Grown In Saline Soil

Certain salt-tolerant crops may be grown in saline soil.

Examples include:

• Barley.
• Cotton.
• Sugar beet.
• Sorghum.
• Alfalfa.
• Rice with tolerant varieties.

Important Features Of Saline Soil

• Also called Usara soil.
• Contains sodium, potassium and magnesium.
• Generally infertile.
• Occurs in arid, semi-arid, waterlogged and swampy areas.
• Lacks nitrogen and calcium.
• Found in western Gujarat, eastern coast deltas and Sundarbans.
• Gypsum is used to treat salinity.

7. Peaty Soils

Peaty soils are found in areas of heavy rainfall and high humidity.

They form where there is dense vegetation and a large amount of dead organic matter accumulates.

Formation Of Peaty Soil

In humid regions, vegetation grows well.

When plants die, large quantities of organic matter accumulate.

Because of excess moisture, decomposition may be slow.

This gives peaty soils a high humus and organic content.

Organic matter in these soils may go up to 40 to 50 per cent.

Colour And Nature

Peaty soils are normally:

• Heavy.
• Black in colour.
• Rich in humus.
• Rich in organic matter.
• Moist in nature.

Distribution Of Peaty Soils

Peaty soils occur widely in:

• Northern Bihar.
• Southern Uttarakhand.
• Coastal areas of West Bengal.
• Coastal areas of Odisha.
• Coastal areas of Tamil Nadu.

Crops Grown In Peaty Soil

Peaty soils can support crops that tolerate moist or acidic conditions.

With proper drainage and fertilizer management, they can support crops such as:

• Potatoes.
• Sugar beet.
• Lettuce.
• Onion.
• Carrot.
• Cotton.
• Soybean.
• Rice.

Important Features Of Peaty Soil

• Found in heavy rainfall and high humidity areas.
• Rich in dead organic matter.
• Organic matter may reach 40 to 50 per cent.
• Heavy and black in colour.
• Found in northern Bihar, southern Uttarakhand and coastal parts of West Bengal, Odisha and Tamil Nadu.

8. Forest Soils

Forest soils are formed in forest areas where sufficient rainfall is available.

Their structure and texture vary according to the mountain environment in which they form.

Texture Of Forest Soils

Forest soils are:

• Loamy and silty on valley sides.
• Coarse-grained on upper slopes.

In snow-bound Himalayan areas, they experience denudation.

There, they are acidic and have low humus content.

However, forest soils found in lower valleys are fertile.

Distribution

Forest soils are common in forested and mountainous regions, especially where rainfall is sufficient.

They are found in different forms depending on:

• Altitude.
• Slope.
• Vegetation.
• Rainfall.
• Temperature.

Crops Grown In Forest Soils

Crops that may be grown in forest soils include:

• Maize.
• Corn.
• Groundnuts.

Important Features Of Forest Soil

• Formed in forest areas.
• Requires sufficient rainfall.
• Texture varies with mountain environment.
• Loamy and silty on valley sides.
• Coarse-grained on upper slopes.
• Acidic and low in humus in snow-bound Himalayan areas.
• Fertile in lower valleys.

Soil Degradation

Soil degradation means decline in soil fertility.

It happens when the nutritional status of soil declines and the depth of soil decreases due to erosion and misuse.

Soil degradation is one of the main reasons for the depletion of India’s soil resource base.

Causes Of Soil Degradation

Soil degradation may be caused by:

• Soil erosion.
• Misuse of soil.
• Overgrazing.
• Deforestation.
• Excess irrigation.
• Salinity.
• Waterlogging.
• Wind erosion.
• Unsuitable farming practices.

The degree of soil degradation varies from place to place depending on:

• Topography.
• Wind velocity.
• Amount of rainfall.

Soil Erosion

Soil erosion means removal of topsoil.

Soil formation and soil erosion usually occur together.

Normally, there is a balance between soil formation and erosion.

But when soil is removed faster than it is formed, soil erosion becomes a problem.

Agents Of Soil Erosion

In heavy rainfall areas, water is the main agent of soil erosion.

In arid and semi-arid areas, wind is the main agent of soil erosion.

Water Erosion

Water erosion mainly takes two forms:

• Sheet erosion.
• Gully erosion.

Sheet Erosion

When topsoil is removed from level land after heavy rainfall, it is called sheet erosion.

It is difficult to notice in the beginning because the soil is removed in thin layers.

Gully Erosion

Gully erosion occurs when running water cuts deep channels into the land.

It is more visible and damaging than sheet erosion.

It makes land uneven and unsuitable for agriculture.

Wind Erosion

Wind erosion is common in arid and semi-arid areas.

Strong winds remove loose soil particles and carry them away.

It is common in dry regions where vegetation cover is poor.

Indian Soils At A Glance

Soil Type	Main Region	Key Feature
Alluvial Soil	Northern plains, river valleys, deltas	Most fertile, depositional soil
Black Soil	Deccan Plateau	Regur, black cotton soil, self-ploughing
Red and Yellow Soil	Deccan, Odisha, Chhattisgarh, middle Ganga plain	Red due to iron, yellow when hydrated
Laterite Soil	Karnataka, Kerala, Tamil Nadu, Odisha, Assam	Formed by leaching, rich in iron oxide
Arid Soil	Western Rajasthan	Sandy, saline, Kankar layers
Saline Soil	Western Gujarat, eastern deltas, Sundarbans	Usara soil, excess salts
Peaty Soil	Bihar, Uttarakhand, West Bengal, Odisha, Tamil Nadu	Rich in humus and organic matter
Forest Soil	Forested mountain areas	Varies with altitude and slope

Soil Nutrients At A Glance

Soil Type	Rich In	Poor In
Alluvial Soil	Potash	Phosphorous
Black Soil	Lime, iron, magnesia, alumina, potash	Phosphorous, nitrogen, organic matter
Red and Yellow Soil	Iron content gives colour	Nitrogen, phosphorous, humus
Laterite Soil	Iron oxide, aluminium compounds, potash	Organic matter, nitrogen, phosphate, calcium
Arid Soil	Normal phosphate, calcium in lower horizons	Moisture, humus, nitrogen
Saline Soil	Sodium, potassium, magnesium	Nitrogen, calcium
Peaty Soil	Humus, organic matter	Depends on acidity and drainage
Forest Soil	Fertile in lower valleys	Humus low in snow-bound areas

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