Geography · India · 17

Soils of India

Soil is the thin layer of material covering the Earth's surface, formed by the weathering of rocks and the decomposition of organic matter over thousands of years. India's diverse climate, parent rock, and topography have produced a remarkable variety of soil types that directly determine agricultural productivity across its regions. The Indian Council of Agricultural Research (ICAR) classifies Indian soils into eight major groups, with Alluvial soil being the most widespread, covering nearly 43% of the total land area. Understanding soil types, their nutrient status, and the crops they support is a high-frequency topic in SSC CGL examinations.

🟤 11 topics🎯 161+ points📝 self-test

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Topic 01

What is Soil and Soil Structure

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Key Point

Soil structure refers to the arrangement of soil particles (sand, silt, clay) into aggregates or peds — it determines pore spaces that influence air circulation, water retention, and root penetration.

Good soil structure is essential for healthy plant growth and soil fertility.

Types of Soil Structure

Structure Type	Key Characteristic
Granular	Small, rounded aggregates; good for crops
Blocky	Block-shaped units; common in subsoils
Prismatic	Vertical columns; found in arid/semi-arid soils
Columnar	Like prismatic but with rounded tops
Platy	Horizontal layers; impedes water movement
Structureless (Single Grain)	Sand particles with no aggregation

📝 Quick self-test 2 MCQs · 2 fill-ups

What does soil structure refer to?

The chemical fertility of the soil
The arrangement of soil particles into aggregates or peds
The colour of the topsoil
The total nutrient content of the soil

✔ B. The arrangement of soil particles into aggregates or peds — Soil structure is the arrangement of soil particles (sand, silt, clay) into aggregates or peds.

Which soil structure type consists of horizontal layers that impede water movement?

Granular
Prismatic
Platy
Columnar

✔ C. Platy — Platy structure has horizontal layers that impede water movement.

The soil structure type has small, rounded aggregates and is good for crops.

✔ Granular

Prismatic soil structure, made of vertical columns, is found in /semi-arid soils.

✔ arid

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Topic 02

Nutrients Required by Soil

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Key Point

Plants need nutrients from soil to grow; Essential Nutrients — C, H, O — are supplied from air and water, not from soil.

Macro Nutrients: N (Nitrogen), P (Phosphorus), K (Potassium), S (Sulphur), Ca (Calcium), Mg (Magnesium) — required in large quantities; also known as major elements; present in excessive concentration but not toxic to the cell.
Micro Nutrients: Zn (Zinc), Cu (Copper), Fe (Iron), Mn (Manganese), B (Boron), Cl (Chloride), Mo (Molybdenum), Co (Cobalt) — required in trace amounts.
Each nutrient has a distinctive role in the soil nutrient cycle.

Macro vs Micro Nutrients

Macro Nutrients	Micro Nutrients
N — Nitrogen	Fe — Iron
P — Phosphorus	Mn — Manganese
K — Potassium	Cu — Copper
S — Sulphur	Zn — Zinc
B (Boron as macro context)	B — Boron
Ca — Calcium	Cl — Chloride
Mg — Magnesium	Mo — Molybdenum

Need of N, P, K (Primary Macronutrients)

Nitrogen (N): helps the plant foliage to grow strong.
Phosphorus (P): helps the roots and flowers to grow and develop.
Potassium (K): important for overall plant health.

📝 Quick self-test 2 MCQs · 2 fill-ups

The essential nutrients C, H, and O are supplied to plants from:

Soil only
Air and water
Fertilizers
Micronutrient sprays

✔ B. Air and water — Essential nutrients C, H, O come from air and water, not from soil.

Which of the following is a macro nutrient?

Zinc
Copper
Nitrogen
Molybdenum

✔ C. Nitrogen — Nitrogen (N) is a macro nutrient required in large quantities.

helps the plant foliage to grow strong.

✔ Nitrogen

Micro nutrients such as Zn, Cu, and Fe are required in amounts.

✔ trace

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Topic 03

ICAR Classification of Indian Soils

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Key Point

ICAR classifies Indian soils into 8 major types; Alluvial soil is the most widespread at 43% of India's land area, decreasing through Red, Black/Regur, Arid/Desert, Laterite, Saline, Peaty/Marshy, Forest, Sub-mountain soils to Snowfields.

The classification is based on parent material, climate, topography, and biological activity.

ICAR Soil Classification — Area Coverage (Decreasing Order)

Rank	Soil Type	Coverage
1	Alluvial Soil	43% (maximum)
2	Red Soil	18.5%
3	Black / Regur Soil	15%
4	Arid / Desert Soil	—
5	Laterite Soil	—
6	Saline Soil	—
7	Peaty / Marshy Soil	—
8	Forest Soil	—
9	Sub-mountain Soil	—
10	Snowfields	(increasing → least)

📝 Quick self-test 2 MCQs · 2 fill-ups

Into how many major types does ICAR classify Indian soils?

✔ B. 8 — ICAR classifies Indian soils into 8 major types.

Which soil is the most widespread in India according to ICAR classification?

Red Soil
Black Soil
Alluvial Soil
Laterite Soil

✔ C. Alluvial Soil — Alluvial soil is the most widespread at 43% of India's land area.

Alluvial soil covers of India's land area, making it the most widespread.

✔ 43%

The ICAR classification is based on parent material, climate, topography, and activity.

✔ biological

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Topic 04

Alluvial Soil

Depositional soil transported and deposited by rivers and streams.
Colour: Light Grey to Ash Grey (dark grey in older deposits).
Texture: Sandy to silty loam or clay.
Rich in: Potash | Poorer in: Phosphorous.
Mainly found in the Indo-Gangetic Plains.

New vs Old Alluvium

Type	Local Name	Character
New Alluvium	Khadar	Lighter, more fertile, near river channels
Old Alluvium	Bhangar	Darker, contains Kankar (calcium carbonate nodules)

Geographical Divisions of Alluvial Soil

Bhabar: coarse gravelly soil at the foothills of Shivaliks; 8–16 km wide; rivers disappear underground here.
Terai: waterlogged, marshy zone below Bhabar; rivers re-emerge.
Bhangar: old alluvium, higher terraces; contains Kankar.
Khadar: new alluvium, low-lying flood plains, renewed annually.

Crops: Rice, Wheat, Sugarcane, Cotton, Jute, Pulses, Oilseeds.

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Key Point

Alluvial soil is the most available (43%) and most fertile soil in India, formed by the deposition of river sediments — it gives better yield output.

📝 Quick self-test 2 MCQs · 2 fill-ups

Alluvial soil is rich in which nutrient?

Phosphorous
Potash
Nitrogen
Iron

✔ B. Potash — Alluvial soil is rich in Potash but poorer in Phosphorous.

What is the local name for new alluvium found near river channels?

Bhangar
Kankar
Khadar
Bhabar

✔ C. Khadar — New alluvium is called Khadar, which is lighter and more fertile.

Alluvial soil is mainly found in the Plains.

✔ Indo-Gangetic

Old alluvium, known as , contains Kankar (calcium carbonate nodules).

✔ Bhangar

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Topic 05

Red Soil

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Key Point

Red soil gets its red/reddish colour from Ferric oxide (Iron oxide); it is the 2nd most widely found soil in India, covering 18.5% of the land.

Found mainly in low rainfall areas.
Also known as the Omnibus Group.
Absence of Kankar (impure calcium carbonate) is a distinguishing feature.
The lower layer is reddish yellow or yellow (due to hydrated form of iron oxide).
Texture: Sandy to clay and loamy.
Crops: Wheat, Cotton, Pulses, Tobacco, Oilseeds, Potatoes, etc.

Key Facts — Red Soil

Feature	Detail
Colour	Red (Ferric oxide / Iron oxide)
Area rank	2nd most widespread
Coverage	18.5%
Texture	Sandy to loamy to clay
Kankar presence	Absent
Main crops	Wheat, Cotton, Pulses, Tobacco, Oilseeds

📝 Quick self-test 2 MCQs · 2 fill-ups

Red soil gets its red colour from:

Aluminium oxide
Ferric oxide (Iron oxide)
Sulphur
Calcium carbonate

✔ B. Ferric oxide (Iron oxide) — Red soil gets its red colour from Ferric oxide (Iron oxide).

Which feature distinguishes Red soil?

Presence of Kankar
Absence of Kankar
High salinity
Black colour

✔ B. Absence of Kankar — The absence of Kankar is a distinguishing feature of Red soil.

Red soil is the most widely found soil in India, covering 18.5% of the land.

✔ 2nd

Red soil is also known as the Group.

✔ Omnibus

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Topic 06

Black Soil (Regur Soil)

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Key Point

Black soil (also called Regur soil) is formed from the weathering of basaltic/volcanic lava rocks; it is the best soil for cotton cultivation and has high water-retaining capacity.

Also known as "Regur" — derived from the Telugu word; covers 15% of India's land.
Most of the Deccan Plateau is occupied by Black soil (Maharashtra, MP, Gujarat, AP, Telangana).
Considered a mature soil.
Colour: Grey to Black.
Texture: Clayey — swells when wet, cracks when dry (self-ploughing nature).
High moisture-retentive capacity — stores water for long periods.
Deficient in: Nitrogen, Phosphorous, and Organic Matter.
Rich in: Calcium, Potassium, Aluminium, Iron.

Key Facts — Black Soil

Feature	Detail
Other name	Regur soil / Cotton soil
Origin	Weathering of basalt / lava rocks
Colour	Grey to Black
Texture	Clayey (self-ploughing)
Water retention	Very High
Best crop	Cotton
Deficient in	Nitrogen, Phosphorous, Organic Matter
Region	Deccan Plateau

📝 Quick self-test 2 MCQs · 2 fill-ups

Black soil is formed from the weathering of:

Granite rocks
Basaltic/volcanic lava rocks
Sandstone
Limestone

✔ B. Basaltic/volcanic lava rocks — Black soil is formed from the weathering of basaltic/volcanic lava rocks.

Black soil is best suited for the cultivation of:

Rice
Wheat
Cotton
Tea

✔ C. Cotton — Black soil is the best soil for cotton cultivation.

Black soil is also called soil, derived from a Telugu word.

✔ Regur

Black soil is deficient in Nitrogen, Phosphorous, and Matter.

✔ Organic

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Topic 07

Laterite Soil

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Key Point

Laterite soil is named from the Latin word "Later" meaning Brick; it forms in regions of high temperature and high rainfall through intense leaching.

Rich in: Iron and Aluminium — red colour is due to Iron.
Lime and Silica are leached away from the soil, leaving behind iron/aluminium oxides.
Poor in fertility — rich in iron and aluminium but poor in plant nutrients.
Found in: Kerala, Karnataka, Tamil Nadu, Assam hills, Orissa, parts of Maharashtra.

Key Facts — Laterite Soil

Feature	Detail
Name origin	Latin "Later" = Brick
Climate	High temp + High rainfall
Rich in	Iron, Aluminium
Colour	Red (due to Iron)
Leached away	Lime, Silica
Use	Bricks/building material when hard
Fertility	Low

📝 Quick self-test 2 MCQs · 2 fill-ups

The name 'Laterite' comes from the Latin word 'Later' meaning:

Red
Brick
Iron
Rock

✔ B. Brick — Laterite is named from the Latin word 'Later' meaning Brick.

Laterite soil is rich in which two elements?

Nitrogen and Phosphorous
Iron and Aluminium
Calcium and Potassium
Lime and Silica

✔ B. Iron and Aluminium — Laterite soil is rich in Iron and Aluminium.

Laterite soil forms in regions of high temperature and high through intense leaching.

✔ rainfall

In laterite soil, and Silica are leached away, leaving behind iron/aluminium oxides.

✔ Lime

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Topic 08

Desert / Arid Soil

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Key Point

Desert/Arid soil is found in Rajasthan and Gujarat; it has the least water-retaining capacity, is sandy in texture, and has high salt and Kankar content.

Colour: Red to Brown.
Lack of moisture and humus — very low organic matter.
Texture: Sandy.
Nitrogen is insufficient; Phosphorous is normal.
Kankar (impure carbonate) content is high.
High salt content; soils are saline in nature.
Least water-retaining capacity among all soil types.

Key Facts — Desert / Arid Soil

Feature	Detail
Location	Rajasthan, Gujarat
Colour	Red to Brown
Texture	Sandy
Water retention	Least / Lowest
Nitrogen	Insufficient
Phosphorous	Normal
Kankar content	High
Humus	Very low (lack of moisture)

📝 Quick self-test 2 MCQs · 2 fill-ups

Desert/Arid soil is mainly found in which states?

Kerala and Karnataka
Rajasthan and Gujarat
West Bengal and Bihar
Maharashtra and MP

✔ B. Rajasthan and Gujarat — Desert/Arid soil is found in Rajasthan and Gujarat.

Which characteristic is true of Desert/Arid soil?

Highest water-retaining capacity
Least water-retaining capacity
Very high humus content
Rich in Nitrogen

✔ B. Least water-retaining capacity — Desert/Arid soil has the least water-retaining capacity.

The texture of Desert/Arid soil is .

✔ Sandy

In Desert/Arid soil, content (impure carbonate) is high.

✔ Kankar

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Topic 09

Peaty / Marshy Soil and Saline Soil

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Key Point

Peaty/Marshy soil is found in areas of high humidity and high rainfall; it contains a large quantity of dead organic matter (humus) and is a heavy soil with black colour.

Peaty / Marshy Soil

In Hindi, known as "Daldal" / "Kichal".
Good for growing crops needing water — e.g., Sugarcane, Rice.
Waterlogged, boggy terrain — common in parts of Kerala, West Bengal, Odisha, Bihar.

Saline Soil

Saline soil contains salinity more than usual — excess salinity is not required by plants and affects plant growth negatively.
Also called Usar / Reh / Thur / Kallar in different regions.
Formed in areas of high evaporation, poor drainage, or due to overuse of fertilizers.
Soil containing salinity more than the usual level; harmful to crops.

Soil	Key Feature	Crops	Location
Peaty/Marshy	High humus, waterlogged, black	Sugarcane, Rice	Kerala, West Bengal, Bihar
Saline	Excess salt, not required by plants	Poor crop yield	Arid/semi-arid + waterlogged areas

📝 Quick self-test 2 MCQs · 2 fill-ups

Peaty/Marshy soil is characterised by a large quantity of:

Salt
Dead organic matter (humus)
Iron oxide
Kankar

✔ B. Dead organic matter (humus) — Peaty/Marshy soil contains a large quantity of dead organic matter (humus).

Saline soil is also known by which of these names?

Khadar
Regur
Usar / Reh
Bhabar

✔ C. Usar / Reh — Saline soil is also called Usar / Reh / Thur / Kallar.

Peaty/Marshy soil is good for growing water-needing crops such as Sugarcane and .

✔ Rice

Saline soil contains more than usual, which affects plant growth negatively.

✔ salinity

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Topic 10

Forest Soil and Mountain Soil

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Key Point

Forest soil is found in regions of high rainfall; it is acidic in nature with less humus content.

Forest Soil

Found on slopes where heavy rainfall leaches nutrients downward.
Humus content is less compared to alluvial or black soils.
Soil is Acidic.

Mountain Soil

Mountain soil is found in mountainous/hilly regions; it is an immature soil (means not good for plants in its natural state) with low humus and acidic character.
Found in the Himalayan region and other mountain ranges.
Immature — thin, skeletal, less weathered; varies with altitude.
Low humus content, acidic.
Less developed; humus and depth increase as we descend to lower slopes.

Soil	Region	Humus	Reaction	Suitability
Forest	High-rainfall slopes	Less	Acidic	Tea, Coffee (hill slopes)
Mountain	Mountainous zones	Low	Acidic	Immature; limited crops

📝 Quick self-test 2 MCQs · 2 fill-ups

Forest soil is generally which in nature?

Alkaline
Acidic
Neutral
Saline

✔ B. Acidic — Forest soil is acidic in nature with less humus content.

Mountain soil is described as:

A mature, fertile soil
An immature soil with low humus
A saline soil
A clayey black soil

✔ B. An immature soil with low humus — Mountain soil is an immature soil with low humus and acidic character.

Forest soil is found in regions of high where nutrients are leached downward.

✔ rainfall

Mountain soil is found in mountainous/hilly regions and is in nature (not good for plants naturally).

✔ immature

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Topic 11

Soil Colour Indications

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Key Point

Soil colour is a diagnostic indicator of its mineral and organic composition — Black colour indicates presence of Iron, Aluminium, and Humus.

Each colour signals a different chemical content in the soil.

Colour Indicators

Soil Colour	Indicates Presence of
Black	Iron, Aluminium, Humus
Grey / Blue-Grey	Waterlogged / Dry conditions
Greenish	Sulphur
Red	Iron, Magnesium, and Sulphur

Black soils are rich in iron, aluminium, and humus (e.g., Black/Regur soil).
Red colour specifically indicates Ferric oxide (iron oxide) dominance.
Greenish tint in soil indicates presence of Sulphur.
Grey/Blue-Grey may indicate waterlogging or extreme dryness.

📝 Quick self-test 2 MCQs · 2 fill-ups

Black colour in soil indicates the presence of:

Sulphur only
Iron, Aluminium, and Humus
Salt and Kankar
Silica and Lime

✔ B. Iron, Aluminium, and Humus — Black colour indicates presence of Iron, Aluminium, and Humus.

A greenish tint in soil indicates the presence of:

Iron
Sulphur
Humus
Potash

✔ B. Sulphur — Greenish colour in soil indicates the presence of Sulphur.

Red colour in soil specifically indicates oxide (iron oxide) dominance.

✔ Ferric

Grey/Blue-Grey soil colour may indicate or extreme dryness.

✔ waterlogging

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Recap

Quick Revision

Alluvial soil covers 43% of India — most widespread and most fertile; mainly in Indo-Gangetic plains.
New alluvium = Khadar; Old alluvium = Bhangar; Bhabar is 8–16 km wide at Shivalik foothills.
Alluvial soil is rich in Potash but poor in Phosphorous.
Red soil gets colour from Ferric oxide (Iron oxide); 2nd most widespread (18.5%); absent Kankar.
Black/Regur soil formed from basaltic lava rocks; best for Cotton; Deccan Plateau; Clayey texture.
Black soil is deficient in Nitrogen, Phosphorous, and Organic Matter.
Laterite soil — named from Latin "Later" (Brick); high rainfall + high temp; rich in Iron and Aluminium; lime/silica leached away.
Desert/Arid soil (Rajasthan, Gujarat) — sandy, Red to Brown, least water retention, high Kankar content.
Peaty/Marshy soil — high humus, waterlogged, black, good for Sugarcane and Rice.
Saline soil — excess salt, harmful to plant growth; also called Usar/Reh.
Forest soil — high rainfall zones, less humus, acidic.
Mountain soil — immature, low humus, acidic; varies with altitude.
Black colour in soil → Iron, Aluminium, Humus; Red → Iron/Magnesium/Sulphur; Greenish → Sulphur.
Macro nutrients (N, P, K, S, Ca, Mg) required in large quantities; Micro nutrients (Fe, Mn, Zn, Cu, B, Cl, Mo) in trace amounts.
ICAR soil order (decreasing area): Alluvial → Red → Black → Arid/Desert → Laterite → Saline → Peaty → Forest → Sub-mountain → Snowfields.

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