Geography Ch08 – Soils of India

📌 Soil Basics

🔬 Key Definitions

Soil Horizon — Layer parallel to surface of soil; different physical, chemical & biological characteristics
Weathering process helps in soil formation
Science of studying soil: Soil Science (Pedology)
ICAR: Indian Council of Agricultural Research — HQ: New Delhi
ICAR divides Indian soil into 8 categories

🚨 Common Indian Soil Deficiencies

All Indian soils commonly lack: Many agricultural soils are low in nitrogen and organic matter; other deficiencies vary by soil and region

📊 8 Soil Types — Area Coverage

~43%

1. Alluvial Soil

~18.5%

3. Red Soil

~15%

2. Black Soil

3.7%

4. Laterite Soil

⚡ AREA ORDER (Highest → Lowest)

Alluvial (~43%) → Red (~18.5%) → Black (~15%) → Laterite (3.7%)

🏛️ Important Soil Institutions

Institution	Established	Purpose
Central Soil Conservation Board	1953	Control soil erosion and harmful effects
Soil Survey	1956	Scientific survey of soils
CAZRI (Central Arid Zone Research Institute)	1959 — Jodhpur	Study for resolving desert problems

🚨 EXAM TRAP

Alluvial = largest area (~43%) — NOT Black or Red
Red soil = 2nd largest (~18.5%) — more than Black (~15%)
CAZRI = Jodhpur (1959) — desert research institute
ICAR HQ = New Delhi (divides into 8 categories)

🟤 1. Alluvial Soil — Most Widespread

Alluvial Soil — ~43% of India

Area: ~43% of the country — most widespread
Formation: Brought by rivers — extremely fertile
Found in: UP, Bihar, West Bengal, Punjab
Northern Plains + Delta of peninsular rivers
Entire Northern Plain + Coastal Plains

ABUNDANCE:

PotashLime

DEFICIENCY:

NitrogenPhosphorusHumus

Major Crops:

Rice

Wheat

Maize

Oilseeds

Pulses

Potato

🔄 Bangar vs Khadar — Types of Alluvial

Feature	Bangar (Old)	Khadar (New)
Age	Old alluvial	New alluvial
Fertility	Less fertile	Extremely fertile
Position	Elevated (upland)	Low-lying flood plain
Texture	Coarse, Kankar (gravel)	Fine silt

⚫ 2. Black Soil (Regur) — Cotton Soil

Black Soil (Regur) — ~15% of India

Area: ~15%
Other name: Regur Soil
Formation: Weathering of Lava (Basalt)
Water retention: Very high moisture-retention capacity
Becomes sticky when wet; cracks appear when dry
Called self-ploughing soil (due to cracks)
Best for: Cotton cultivation — "Black Cotton Soil"

ABUNDANCE:

IronLimeAluminiumMagnesium

DEFICIENCY:

NitrogenPhosphorusOrganic matter

Found In:

Gujarat

Maharashtra

W. Madhya Pradesh

Deccan Plateau

Other Crops:

Cotton ★

Wheat

Jowar

Sugarcane

🚨 EXAM TRAP

Black soil = formed from Basalt lava (Deccan Trap) — NOT red volcanic
Black soil = very high moisture retention — NOT alluvial
Self-ploughing = Black soil (cracks when dry)
Khadar = more fertile than Bangar (new alluvial)
Bihar, UP, WB = Alluvial soil — very important for BPSC!

🔴 3. Red Soil — 2nd Largest Area

Red Soil — ~18.5% of India

Area: ~18.5% — 2nd largest
Formation: Disintegration of igneous & metamorphic rocks
Red colour due to: Iron oxide
Appears yellow when hydrated
Nature: Generally neutral to acidic; more acidic in wetter settings
Found in: water-scarce areas
Belongs to: Omnibus soil group

ABUNDANCE:

SilicaIron

DEFICIENCY:

NitrogenPhosphorusHumus

Found In:

Karnataka

Tamil Nadu

Maharashtra

W. Ghats region

Major Crops:

Cotton

Wheat

Pulses

Coarse Grains

🟫 4. Laterite Soil — Leached Soil

Laterite Soil — 3.7% of India

Area: 3.7%
Formation: Leaching process from heavy rainfall (High temp + High rainfall)
Found in: Tropical regions, developed on igneous base rocks
Colour: Red

ABUNDANCE:

Iron oxidesAluminium oxidesSilica leached

DEFICIENCY:

NPLime / calciumOrganic matterPotash varies

Types of Laterite:

Type	Feature
Deep Red Laterite	Traditionally: relatively high iron oxide and potash, low kaolin; poor fertility
White Laterite	Least fertile; White = Kaolinite (Clay mineral)
Underground Laterite	Traditionally relatively more fertile; iron compounds move downward and accumulate lower in the profile

Found In:

Tamil Nadu

Andhra Pradesh

Kerala

Assam

Meghalaya Hills

Major Crops:

Tea ★

Rubber

Cashew

🚨 EXAM TRAP

Red soil = iron oxide makes it red | Turns yellow when hydrated
Red soil = generally neutral to acidic; traditionally called an Omnibus group
Laterite = formed by leaching (NOT lava like Black soil)
White Laterite = least fertile (white due to Kaolinite)
Tea + Rubber = Laterite soil — NOT alluvial
Red soil = 2nd largest (~18.5%) — more than Black soil (~15%)

🏜️ Remaining 4 Soil Types

5. Marshy / Peaty Soil

Found in: Coastal regions
Condition: Heavy rainfall + High humidity
Abundance: Organic matter (Humus)

6. Desert Soil

Found in: areas with <50 cm rainfall
States: W. Rajasthan, Gujarat, Haryana
Abundance: Soluble salts may be high; phosphate generally normal
Deficiency: Low nitrogen, humus/organic matter and moisture

7. Saline / Alkaline Soil

Found in: AP, Karnataka, Bihar, UP, Haryana, Punjab, RJ, MH, Gujarat
Abundance: Sodium, Magnesium, Potassium
Deficiency: Nitrogen and calcium
Dry type: Sandy + Saline → Rajasthan, Punjab, Gujarat

8. Mountain / Forest Soil

Found in: Mountain / Forest regions
Humus varies: lower forested zones may be humus-rich; snow-bound upper soils can be low-humus
Properties vary with altitude and relief; lower valleys may be fertile

🔑 Special Features — Quick Reference

Unique Feature	Soil Type
Very high moisture retention	Black Soil (Regur)
Self-ploughing (cracks when dry)	Black Soil
Most widespread (~43%)	Alluvial Soil
Formed by leaching	Laterite Soil
Formed by lava weathering	Black Soil
Red colour due to iron oxide	Red Soil
Turns yellow when hydrated	Red Soil
Acidic nature	Red Soil
Best for cotton	Black Soil
Best for tea/rubber/cashew	Laterite Soil
Omnibus soil group	Red Soil
White = Kaolinite (least fertile)	White Laterite
Richest in Humus	Marshy/Peaty Soil

🚨 EXAM TRAP

Saline soil found in Bihar also — BPSC important!
Desert soil = soluble salts may be high; phosphate generally normal; low nitrogen, humus and moisture
Marshy soil = rich in Organic matter / Humus (coastal areas)
Mountain/forest soils vary with altitude: upper snow-bound soils may be acidic and low-humus; lower valleys can be fertile

📊 Master Summary — All 8 Soil Types

#	Soil Type	% Area	Formation	Abundance	Deficiency	Major Crops	Found In
1	Alluvial	~43%	River deposits	Potash, Lime	N, P, Humus	Rice, Wheat, Maize, Pulses, Potato	UP, Bihar, WB, Punjab, N.Plains, Coasts
2	Black (Regur)	~15%	Lava (Basalt) weathering	Fe, Lime, Al, Mg	N, P, organic matter	Cotton★, Wheat, Jowar, Sugarcane	Gujarat, MH, W.MP, Deccan
3	Red	~18.5%	Igneous/Metamorphic rock disintegration	Silica, Iron	N, P, Humus	Millets, groundnut, pulses, tobacco	TN, Karnataka, Andhra–Telangana, Odisha, CG, Jharkhand
4	Laterite	3.7%	Leaching (high temp + rain)	Iron and aluminium oxides; silica leached	OM, N, P, lime/calcium low; potash varies	Tea★, Coffee, Cashew; Rubber in suitable humid tracts	TN, AP, Kerala, Assam, Meghalaya
5	Marshy/Peaty	—	Heavy rain + high humidity	Organic matter	—	Coastal crops	Coastal regions
6	Desert	—	Arid conditions (<50cm rain)	Soluble salts may be high; phosphate generally normal	Low N, organic matter and moisture	—	W.Rajasthan, Gujarat, Haryana
7	Saline/Alkaline	—	—	Na, Mg, K	Nitrogen and calcium	—	AP, KA, Bihar, UP, HR, PB, RJ, MH, GJ
8	Mountain/Forest	—	—	Humus varies; often lower in snow-bound upper zones	Variable with altitude and relief	—	Mountain/Forest regions

🎯 Crop–Soil Mapping

Crop	Best Soil
Cotton	Black Soil (Regur) — strongest cotton association
Rice, Wheat, Maize	Alluvial Soil
Tea, Rubber, Cashew	Laterite Soil
Jowar, Sugarcane	Black Soil
Pulses	Alluvial + Red Soil
Potato	Alluvial Soil

⚡ MASTER RECALL — Deficiency Pattern

N + P + Humus deficient → Alluvial, Red soils
N + P + organic matter commonly low → Black soil
Low organic matter + N + P + lime/calcium → Laterite; potash varies
Saline/Alkaline soil → commonly deficient in nitrogen and calcium
Low N + humus/organic matter + moisture → Desert soil
Mountain/Forest soil → properties vary with altitude and relief

📍 Bihar Special — Soil for BPSC

🌾 Bihar = Alluvial Soil State

Bihar is covered predominantly by Alluvial Soil
Deposited by rivers: Ganga, Kosi, Gandak, Son, Ghagara
Bihar's northern plains = Khadar (new alluvial) — extremely fertile
Bihar's upland areas = Bangar (old alluvial) — less fertile
Bihar's alluvial soil supports: Rice, Wheat, Maize, Potato, Pulses

Rice

Kharif Season

Wheat

Rabi Season

Maize

Kharif, Rabi and summer

⚠️ Saline Soil in Bihar

Bihar also has Saline/Alkaline soil in some areas
Locally called "Usar" soil in UP-Bihar region
Abundance: Sodium, Magnesium, Potassium
Deficiency: Nitrogen and calcium
Problem for agriculture — needs soil reclamation

🏔️ Chotanagpur Plateau — Red Soil (Jharkhand Border)

Chotanagpur Plateau (Jharkhand) = Red Soil area
Formed from: Igneous + Metamorphic rocks
Near Bihar's Jharkhand border area
Less fertile but supports: Coarse grains, Pulses

🌿 Key Bihar Alluvial Soil Facts

Alluvial soil = Potash + Lime abundant (good for Rabi crops)
Generally nitrogen and phosphorus can be limiting; organic matter varies locally
Kosi floods deposit new Khadar soil (fertile but floods are destructive)
Son valley floor = mainly alluvium; red/yellow soils become important at adjoining plateau margins
Bihar = rice bowl of Eastern India due to alluvial soil

⚡ BPSC MASTER RECALL — Bihar Soils

Bihar = primarily Alluvial Soil (N.Plains)
N.Bihar flood plain = Khadar (most fertile)
Some areas = Saline (Usar) soil — problem land
Jharkhand border = Red Soil (Chotanagpur)
Bihar alluvial crops: Rice, Wheat, Maize, Potato
Commonly low N and organic matter; phosphorus and other nutrients vary with soil and region

🚨 EXAM TRAP

"Usar" soil = Saline/Alkaline — found in Bihar + UP
Khadar is generally more fertile than Bangar and is widespread across the active floodplains of northern Bihar.
Alluvial soil = Potash + Lime abundant (NOT Nitrogen)
Many soils in Bihar are deficient in nitrogen, phosphorus and humus, increasing the need for soil-nutrient management and fertilisers.
The Indian Council of Agricultural Research is headquartered in New Delhi, while the Central Arid Zone Research Institute is headquartered in Jodhpur.

🌱 Indian Geography — Chapter 08