Indian Soils
India's eight major soil types — alluvial, black, red, laterite, arid, saline, peaty, forest — their distribution, properties, and UPSC-relevant crop associations.
What is Soil?
- Soil = the thin top layer of the Earth's crust comprising rock particles mixed with organic matter — a complex natural resource that sustains life by supporting plant growth, regulating water flow, and providing habitat for organisms.
- Pedology = the scientific study of soils in their natural environment.
- Pedogenesis = the natural process of soil formation — includes weathering, leaching, calcification, humification, and other processes acting over thousands to millions of years.
Soil Texture — Basic Types
Classified by the proportion of particles of various sizes:
| Type | Dominant Particle | Key Property |
|---|---|---|
| Sandy | Large particles (0.05–2 mm) | Drains quickly; light-coloured; low organic matter; dry; well-aerated |
| Clayey | Fine particles (<0.002 mm) | Holds water tightly; little air; heavy; high water retention |
| Loamy | Mix of sand, clay, silt | Best for farming — right drainage + water-holding capacity |
| Silty | Medium particles (0.002–0.05 mm) | Deposited in riverbeds; very fertile; smooth texture |
- Ideal agricultural topsoil = Loam — balanced mix of sand, clay, and silt, with humus.
- Humus = dark organic matter from decayed plant/animal remains; holds water + nutrients; acts as natural fertiliser.
Crop–Soil Texture Preference
| Crop | Preferred Soil |
|---|---|
| Paddy (Rice) | Clayey + rich organic matter; high water retention |
| Wheat, Gram | Clayey or loamy |
| Cotton | Sandy loam or loam; good drainage + aeration |
| Lentils/Pulses | Loamy soils with easy drainage |
Soil Profile (Soil Horizons)
A vertical section through soil layers is called the soil profile. Each layer = a horizon, distinguished by colour, texture, depth, and chemical composition.
| Horizon | Name | Description |
|---|---|---|
| O | Organic layer | Dominated by organic material — undecomposed or partially decomposed litter (leaves, twigs, needles, mosses). Present above mineral soil. |
| A | Topsoil / Surface soil | Organic matter mixed with minerals; dark colour due to high organic content; richest in life; layer of eluviation (loss of clay, iron, aluminium downward) |
| E | Eluviation layer | Significantly leached of clay, iron, and aluminium oxides; concentration of resistant minerals (quartz) left behind; lighter colour; found in older well-developed soils between A and B |
| B | Subsoil | Zone of illuviation — accumulates clay, iron, aluminium, organic compounds leached from above; higher clay content than A horizon; harder and more compact |
| C | Parent material | Large, unbroken rock fragments; weathered parent material; transition between soil and bedrock; accumulates soluble inorganic compounds |
| R | Bedrock | Continuous hard rock masses; the ultimate foundation for soil; not part of true soil profile |
Eluviation = movement of minerals OUT of a horizon (downward by percolating water). Illuviation = accumulation of minerals IN a horizon (deposited from above).
Factors Influencing Soil Formation in India
| Factor | Role |
|---|---|
| Parent Material | Determines colouration, mineral composition, texture of initial soil |
| Relief | Steep slopes → erosion, thin soils; gentle slopes/plains → deep, fertile soils |
| Climate | Temperature + rainfall determine weathering intensity, water percolation, micro-organisms |
| Natural Vegetation | Adds organic matter (humus); protects from erosion; influences soil moisture |
| Time | Longer weathering → more mature soils (peninsular soils more mature than alluvial soils) |
Parent Material Categories in India
| Type | Description | Soil Formed |
|---|---|---|
| Ancient crystalline and metamorphic rocks | Oldest (Pre-Cambrian, ~4 billion years); granites, gneisses, schists; form 'Basement Complex' of Peninsular India; rich in ferromagnesium minerals | Red soils (iron oxide released on weathering) |
| Cuddapah and Vindhyan rocks | Ancient sedimentary rocks (4,000 m thick) | Calcareous (calcium carbonate) + argillaceous (clay) soils; devoid of metalliferous minerals |
| Gondwana rocks | Younger sedimentary rocks | Comparatively less mature soils; low fertility; fairly uniform |
| Deccan Basalts | Volcanic rocks (Deccan Traps); rich in titanium, magnetite, aluminium, magnesium | Black cotton soils (regur) — dark colour due to titaniferous magnetite |
| Tertiary + Mesozoic sedimentary rocks | Younger rocks of extra-peninsular India (plains + Himalayas) | Immature alluvial soils; high porosity; little relation to parent rock |
| Recent and sub-recent deposits | River-deposited material (Quaternary) | Recent alluvial soils; most fertile |
Climate → Soil Colour Relationship (Important!)
| Climate Condition | Soil Type | Why |
|---|---|---|
| High rainfall + high temperature | Red / Laterite | Iron + aluminium oxides concentrated at surface by alternating leaching (wet) and capillary rise (dry); silica leached away |
| Low rainfall + high temp (arid/semi-arid) | Light-coloured soils | Evaporation > precipitation; little humus; pedocal (lime-accumulating) soils |
| Hot summer + low rainfall (Tamil Nadu) | Black soils | Even on non-basaltic parent rock; climatic conditions create similar regur-type soil |
| Arid climate (Rajasthan) | Sandy soils | Both granite and sandstone produce sandy soil under arid conditions — climate overrides parent rock |
| Alternate wet + dry (tropical) | Laterite | Leaching + capillary action alternately → iron/aluminium baking into brick-hard surface |
Peninsular vs. Extra-Peninsular Soils
| Feature | Peninsular Soils | Extra-Peninsular (Alluvial) Soils |
|---|---|---|
| Formation | In situ — from underlying bedrock directly | Transported and deposited by rivers and wind |
| Type | Sedentary / Residual soils | Transported / Azonal soils |
| Maturity | More mature | Less mature (recent origin) |
| Fertility | Generally less fertile (coarse-grained) | Highly fertile (fine silt + clay replenished by floods) |
| Depth | Generally shallow | Very deep |
Major Soil Groups of India
Standard UPSC classification (ICAR-NBSS&LUP, based on NCERT): 8 major groups.
| # | Soil Type | Area (lakh km²) | % of India |
|---|---|---|---|
| 1 | Alluvial | ~15.0 | 45.6% |
| 2 | Black (Regur) | 5.46 | 16.6% |
| 3 | Red | ~3.5 | 10.6% |
| 4 | Laterite/Lateritic | 2.48 | 7.5% |
| 5 | Forest/Mountain | 2.85 | 8.67% |
| 6 | Arid/Desert | 1.42 | 4.32% |
| 7 | Saline/Alkaline | ~0.68 | ~2.07% |
| 8 | Peaty/Marshy | <0.22 | <0.67% |
1. Alluvial Soils
Largest soil group in India — covers ~45.6% of total land area.
Formation
- Formed mainly by silt deposited by Indo-Gangetic-Brahmaputra rivers — classic transported/azonal soils.
- Parent material: Rocks of the Himalayas, eroded and carried downstream.
- In coastal regions: formed by wave action and river delta deposition.
Characteristics
- Immature with weak profiles due to recent origin.
- Mostly loamy; sandy and clayey also occur.
- Porous — loamy nature gives good drainage + aeration.
- Recurrently replenished by floods — explains sustained fertility.
- Pebbly/gravelly soils rare.
- Kankar (calcareous concretions) beds present in some river terraces.
Chemical Properties
| Property | Status |
|---|---|
| Nitrogen | Low |
| Potash, Phosphoric acid, Alkalis (lime) | Adequate |
| Iron oxide and lime | Variable (widely) |
| Humus | Variable; generally moderate |
Distribution
- Indo-Gangetic-Brahmaputra plains (Punjab → UP → Bihar → Bengal → Assam) — except where covered by desert sand.
- Deltas of Mahanadi, Godavari, Krishna, Cauvery — called deltaic alluvium or coastal alluvium.
- Narmada and Tapti valleys and northern Gujarat.
Geological Sub-types (Critical for UPSC)
| Sub-type | Description | Characteristics |
|---|---|---|
| Khadar | New / Younger alluvium — deposited by recent floods; closer to river channels | Light-coloured; fine texture; renewed every flood season; more fertile |
| Bhangar | Old / Older alluvium — above flood level; terrace deposits | Darker; coarser; contains Kankar nodules; less frequently replenished |
Crops in Alluvial Soils
Rice, wheat, sugarcane, tobacco, cotton, jute, maize, oilseeds — most productive agricultural soils of India; support >40% of India's population.
2. Black Soils (Regur / Black Cotton Soil)
Best known for cotton cultivation — also called regur.
Formation
- Primary parent material: Deccan basalts (volcanic rocks) — Deccan Traps formed by fissure volcanic eruptions.
- In Tamil Nadu: gneisses and schists are parent material (climate effect dominates over parent rock).
- Characteristic of hot temperatures + low rainfall — typical of dry/hot peninsular regions.
Characteristics
- Highly argillaceous — clay factor >62%; extremely high water retention.
- In summer: cracks deeply (broad, deep cracks) → lower layers retain moisture; oxygenation down to depth.
- In rainy season: swells greatly → becomes very sticky; ploughing becomes difficult.
- Upland black soils = low fertility; valley black soils = very fertile.
- Has been used for centuries for cotton without manure — very slow exhaustion rate.
Colour
- Black due to presence of titaniferous magnetite (titanium + iron compound) in parent Deccan basalt.
- In Tamil Nadu/AP: black colour from crystalline schists and basic gneisses.
Chemical Composition
| Constituent | Percentage |
|---|---|
| Alumina | ~10% |
| Iron oxide | ~10% |
| Lime + Magnesium carbonates | 6–8% |
| Potash | <0.5% (variable) |
| Phosphates, Nitrogen, Humus | Low |
Distribution
- 5.46 lakh km² (16.6% of India) — Maharashtra (largest single block), Madhya Pradesh, parts of Karnataka, Telangana, Andhra Pradesh, Gujarat, Tamil Nadu.
Crops
Cotton (primary), wheat, jowar, linseed, Virginia tobacco, castor, sunflower, millets; rice + sugarcane where irrigation available.
[UPSC Prelims 2021] Black cotton soil of India has been formed due to weathering of: a) Brown forest soil b) Fissure volcanic rock c) Granite and schist d) Shale and limestone Answer: b) ✓ — Deccan Traps (fissure volcanic eruption) is the primary parent material. Tamil Nadu is the exception (gneisses/schists), but the correct general answer is fissure volcanic rock.
3. Red Soils
Second most widespread soil type; acidic and poor in nutrients.
Formation
- Parent rocks: crystalline and metamorphic rocks — acid granites, gneisses, quartzites.
- Formed in regions of low rainfall where leaching is limited.
- Ancient pre-Cambrian basement rocks → iron oxide released on weathering → red colour.
Characteristics
- Texture varies from sand to clay; majority loamy.
- Uplands: poor, gravelly, porous (shallow soil + intense erosion).
- Lowlands/valleys: rich, deep, dark, fertile.
- Cannot retain water like black soils.
Colour
- Red due to iron oxide (ferric oxide / Fe₂O₃).
- Red colour is more due to wide diffusion (dispersal throughout) of iron oxide, not high concentration.
Chemical Properties
- Acidic (acidic parent rocks).
- Poor in: lime, magnesia, phosphates, nitrogen, humus.
- Fairly rich in: potash and potassium.
Distribution
- 3.5 lakh km² (10.6%): almost all of Tamil Nadu, parts of Karnataka, SE Maharashtra, Telangana, AP, MP, Chhattisgarh, Odisha, Chota Nagpur plateau, south Bihar, West Bengal, UP, Aravallis, eastern Rajasthan (Mewar/Marwar Plateau), parts of Northeast states.
Crops
With proper fertilisers + irrigation: cotton, wheat, rice, pulses, millets, tobacco, oilseeds, potatoes, fruits.
[UPSC Prelims 2010] Red soil colour is mainly due to: a) Abundance of magnesium b) Accumulated humus c) Presence of ferric oxide d) Abundance of phosphates Answer: c) ✓ — Fe₂O₃ (iron III oxide / haematite) gives the characteristic red/reddish-brown colour.
4. Laterite and Lateritic Soils
End-products of intense tropical weathering — ironically infertile despite heavy rainfall areas.
Formation
- Formed under high temperature + heavy rainfall with alternating wet and dry periods.
- Heavy rain → leaching (lime and silica washed away) → residue of iron and aluminium oxides (sesquioxides).
- In dry season: evaporation + capillary action brings iron/aluminium oxides to surface → baked hard.
- Name: "Laterite" from Latin later = brick — hardens on losing moisture; can literally be cut into bricks.
Chemical Composition
- Rich in: Bauxite (aluminium oxide), ferric oxides.
- Very poor in: Lime, magnesia, potash, nitrogen.
- Sometimes: High phosphate content (as iron phosphate).
- In wetter areas: higher humus content.
Characteristics
- Red in colour; little clay, more gravel of red sandstone.
- Hardens greatly on drying — once hardened, durable as building material (historic use in Kerala, Karnataka temples, Portuguese churches, and colonial buildings).
- Cannot be further weathered once laterised.
Distribution
- 2.48 lakh km² (7.5%) — continuous stretches on summits of Western Ghats (1,000–1,500 m), Eastern Ghats, Rajmahal Hills, Vindhyan and Satpura ranges, Malwa Plateau.
- Also: south Maharashtra, Karnataka, and scattered other regions.
Crops
- Too leached for most crops; low fertility.
- With manuring + irrigation: tea, coffee, rubber, cinchona, coconut, arecanut (plantation crops adapted to acidic, well-drained laterite).
- Some areas support grazing grounds and scrub forests.
[UPSC Prelims 2013] Which statements about laterite soils are correct?
- Generally red in colour ✓
- Rich in nitrogen and potash ✗ (very poor in these)
- Well-developed in Rajasthan and UP ✗ (developed in W Ghats, E Ghats, Rajmahal Hills)
- Tapioca and cashew nuts grow well ✓ (tolerant of acidic, low-nutrient soils; deep roots) Answer: c) 1 and 4 ✓
5. Forest and Mountain Soils
Formation
- Formation governed by characteristic deposition of organic matter from forest cover.
- Highly heterogeneous — character changes with parent rock, ground configuration, organic decomposition, mineral weathering, and climate.
- Can differ greatly even in close proximity.
Distribution
- 2.85 lakh km² (8.67%) — Himalayan valleys and less steep/north-facing slopes (south-facing slopes too steep for soil retention); Western and Eastern Ghats.
- South-facing Himalayan slopes: very steep, heavily eroded → minimal soil development.
Chemical Properties
- Very rich in humus (thick forest litter).
- Deficient in: potash, phosphorus, lime.
- Need considerable fertilisers for good yields.
Crops
| Region | Crops |
|---|---|
| Peninsular hills (W/E Ghats) | Tea, coffee, spices, tropical fruits |
| Himalayan forest region | Wheat, maize, barley, temperate fruits (apple, pear, plum) |
6. Arid and Desert Soils
Composition and Formation
- Aeolian sand (90–95%) + clay (5–10%); formed under wind action in arid zones.
- Cover 1.42 lakh km² (4.32%).
- Desertification of neighbouring soils common due to intrusion of aeolian (wind-blown) sand.
Distribution
- Arid/semi-arid Rajasthan, Punjab, Haryana — sand blown from Indus basin + coast by SW monsoon winds.
- Sandy soils (without clay) also in coastal regions of Odisha, Tamil Nadu, Kerala.
Chemical Properties
| Property | Status |
|---|---|
| Organic matter | Poor |
| Calcium carbonate | Present (alkaline tendencies) |
| Calcium gradient | Increases downwards; subsoil has 10× more calcium than topsoil |
| Phosphate content | As high as normal alluvial soils |
| Nitrogen | Low, but some available as nitrates |
Crops
- Drought-resistant + salt-tolerant crops: barley, cotton, millets, maize, pulses.
- Phosphates + nitrates make these soils fertile wherever moisture is available — reclamation with irrigation possible.
7. Saline and Alkaline Soils
Formation
Two main processes:
- Poor drainage + waterlogging — water with high salt concentration stagnates; salts deposited in topsoil after evaporation.
- High sub-soil water table + capillary rise — during dry season, capillary action brings salt-laden water from below to surface; water evaporates; salts remain → infertile crust.
Also: in coastal areas, storm surges during cyclones push saline sea water inland → soil contamination.
Distribution
- ~68,000 km² (2.07%) — canal-irrigated areas and high sub-soil water table areas.
- States affected: Andhra Pradesh, Telangana, Karnataka, Bihar, Uttar Pradesh, Haryana, Punjab (excess irrigation side-effect), Rajasthan, Maharashtra.
- Gujarat: Gulf of Khambhat — tidal saline deposits; estuaries of Narmada, Tapi, Mahi, Sabarmati affected.
- Coastal AP and Tamil Nadu: cyclone storm surges cause periodic soil salinisation.
Why Excess Irrigation Causes Saline Soils
Excess water → raises the sub-soil water table → during dry season, capillary action brings salt-laden groundwater to surface → evaporation leaves salt crust → waterlogging + soil salinity (common in canal-commanded areas of Punjab and Haryana).
8. Peaty and Marshy Soils
Characteristics
- Large amount of organic matter + considerable soluble salts.
- Black, heavy, highly acidic.
- Most humid regions of India.
- Most are waterlogged during rainy season; drained and used for paddy cultivation after monsoon.
- Deficient in: potash and phosphate.
Distribution
- Kottayam and Alappuzha districts of Kerala (kuttanad — below sea-level paddy cultivation).
- Coastal Odisha and Tamil Nadu.
- Sundarbans of West Bengal.
- Bihar (Mithila region).
- Almora district, Uttarakhand.
Soil Degradation in India
Scale of the Problem (Latest Data)
| Metric | Value | Source |
|---|---|---|
| Total degraded land | 97.85 million ha (29.7%) of India's geographical area | SAC/ISRO Land Degradation Atlas, 2021 |
| Desertification | 83.69 million ha (2018–19) — up from 81.48 Mha (2003–05) | MoEFCC |
| Water erosion | 11.01% of land | SAC 2021 |
| Vegetation degradation | 9.15% | SAC 2021 |
| Wind erosion | 5.46% | SAC 2021 |
| Flooding/waterlogging | ~14 million ha | Estimates |
| Soil acidification | ~16 million ha | Estimates |
Causes of Soil Degradation
| Cause | Mechanism |
|---|---|
| Water erosion | Heavy monsoon rainfall on bare/deforested slopes; rills and gullies; Chambal ravines, NE hill slopes |
| Wind erosion | Thar desert; aeolian sand movement |
| Waterlogging + salinisation | Excess irrigation raises water table; capillary salt rise |
| Desertification | Encroachment of aeolian sand into semi-arid zones |
| Jhum (shifting) cultivation | NE India — clears forest patches, leaves soil exposed |
| Mining and construction | Topsoil stripping in mineral-rich regions (Chota Nagpur, Odisha) |
| Overgrazing | Destroys vegetation cover → erosion |
| Chemical degradation | Excessive chemical fertilisers → soil acidification, nutrient imbalance |
Soil Conservation and Government Initiatives
India's Land Degradation Neutrality (LDN) Target
- India pledged at UNCCD COP to restore 26 million hectares of degraded land by 2030 (Bonn Challenge commitment).
- Progress: ~18.94 million ha already restored (as per last available data).
- LDN principle: any new degradation to be balanced by equal restoration elsewhere → net zero land degradation.
Soil Health Card (SHC) Scheme
| Detail | Value |
|---|---|
| Launched | 19 February 2015 at Suratgarh, Rajasthan — by PM Modi |
| 10th Anniversary | February 2025 |
| Type | Centrally Sponsored Scheme (Ministry of Agriculture) |
| Purpose | Issue soil health cards to every farmer — tests 12 parameters (N, P, K, pH, organic carbon, S, Zn, B, Fe, Mn, Cu, EC) |
| Cycle | Every 2 years |
| Village labs (Feb 2025) | 665 village-level soil testing labs in 17 states |
| School labs | 1,000+ soil testing labs in schools |
| Outcome | Enables farmers to apply precise fertiliser doses → reduces over-application → saves money + prevents soil damage |
Other Key Programmes
| Programme | Focus |
|---|---|
| Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) | Efficient irrigation (drip/sprinkler) → reduces waterlogging and salinity |
| National Action Programme to Combat Desertification (NAPCD) | Address desertification in arid/semi-arid zones |
| Watershed Development (IWMP) | Integrated watershed management — check soil erosion |
| Green India Mission | Increasing forest/tree cover → reduces water erosion |
| PM PRANAM scheme | Promote alternative fertilisers → reduce chemical load on soils |
UPSC Corner
Key One-Liners for Prelims
- Largest soil group: Alluvial soils — ~45.6% of India — support >40% of population
- Alluvial soils = transported/azonal soils; peninsular soils = sedentary/residual soils
- Khadar = new alluvium (closer to river, flooded often, more fertile); Bhangar = old alluvium (terrace, Kankar nodules, less fertile)
- Black soil = parent material is Deccan basalt (fissure volcanic rocks); clay >62%; cracks in summer; best for cotton
- Black soil colour = due to titaniferous magnetite (iron-titanium compound in parent Deccan basalt)
- Regur = another name for black cotton soil; also called cotton soil
- Red soil colour = ferric oxide (Fe₂O₃) — wide diffusion, not concentration
- Laterite = Latin for brick; formed by alternating wet-dry leaching; hardens on drying
- Laterite rich in: bauxite + ferric oxides; poor in: lime, magnesia, potash, nitrogen
- Laterite formation requires: high rainfall + high temperature + alternating wet and dry
- Peaty soils = acidic + rich organic matter; found in Kottayam/Alappuzha (Kerala), Sundarbans (WB)
- Saline soils = caused by: poor drainage, excess irrigation, high water table + capillary rise, cyclone storm surges
- India's degraded land = ~97.85 million ha (29.7%) — SAC/ISRO 2021 assessment
- India's LDN restoration target = 26 million ha by 2030 (Bonn Challenge)
- Soil Health Card Scheme launched: 19 February 2015, Suratgarh, Rajasthan; 10th anniversary February 2025
Mains GS1/GS3 Questions
- "Describe the distribution of alluvial soils in India. How does the Khadar-Bhangar division determine agricultural potential?" [GS1 type]
- "What are laterite soils? Explain their formation and why they are unsuitable for conventional agriculture despite forming in high-rainfall areas." [GS1 type]
- "Soil degradation is a serious environmental and food security challenge in India. Discuss its causes, extent, and the government's measures to address it." [GS3 type]
- "Examine the factors responsible for the formation and characteristics of black cotton soils. How do these soils support agriculture in the Deccan plateau?" [GS1 type]
MCQ Trap Awareness
- Trap: "Black soil is formed from granite and schist" → Partially wrong — Deccan basalt (fissure volcanic rock) is the primary parent material; Tamil Nadu is an exception where gneisses/schists can form black soil under hot+dry climate.
- Trap: "Red soil is red due to high iron content" → Wrong — red colour is due to wide diffusion of ferric oxide, not necessarily high iron percentage.
- Trap: "Laterite soils are fertile because of high rainfall" → Wrong — heavy rainfall causes leaching, making them infertile despite forming in high-rainfall zones.
- Trap: "Laterite soils are found mainly in Rajasthan and UP" → Wrong — found in W Ghats, E Ghats, Rajmahal Hills; Rajasthan has desert/arid soils.
- Trap: "Khadar is older alluvium" → Wrong — Khadar = new/younger alluvium; Bhangar = old alluvium.
- Trap: "Alluvial soils are sedentary soils" → Wrong — alluvial soils are transported/azonal soils; peninsular soils are sedentary.
- Trap: "Black soils crack during rainy season" → Wrong — black soils crack during the dry/summer season when moisture evaporates; they swell and become sticky in rainy season.
- Trap: "India's soil degradation is 147 million ha" → Use 97.85 million ha (SAC 2021) for the most official cited figure; 147 Mha is an older estimate from different sources with broader degradation definitions.
- Trap: "Saline soils occur only in coastal areas" → Wrong — they extensively occur in canal-irrigated areas (Punjab, Haryana, UP) due to excess irrigation and waterlogging.
- Trap: "Peaty soils are deficient in nitrogen" → Wrong — peaty soils are rich in organic matter (but deficient in potash and phosphate).
Alluvial soils are India's largest soil group, covering ~45.6% of the total land area. They are transported/azonal soils deposited by the Indo-Gangetic-Brahmaputra rivers and support over 40% of India's population.
Khadar is new/younger alluvium deposited closer to river channels — lighter, finer, more fertile and regularly replenished. Bhangar is older alluvium on terraces above flood level, darker, coarser, and contains Kankar (calcareous) nodules.
Black soils (Regur/Black Cotton Soil) are formed primarily from Deccan basalt (fissure volcanic rocks). Their black colour is due to titaniferous magnetite in the parent rock. Clay content exceeds 62%; they crack in summer and swell in the rainy season.
Black soils are deficient in phosphates, nitrogen, and humus, but adequate in potash and lime. Maharashtra has the largest single block of black soils; they are best suited for cotton cultivation.
Red soils get their colour from wide diffusion of ferric oxide (Fe₂O₃) — not from high iron concentration. They form from crystalline and metamorphic rocks (acid granites, gneisses) and cover ~10.6% of India.
Laterite soils form under high temperature, heavy rainfall, and alternating wet-dry cycles. Heavy rain leaches lime and silica; iron and aluminium oxides accumulate and bake hard on drying. The name comes from the Latin 'later' (brick) — they are literally cut into bricks for construction.
Laterite soils are rich in bauxite and ferric oxides but very poor in lime, magnesia, potash, and nitrogen. Despite forming in high-rainfall areas, leaching makes them infertile. Tea, coffee, rubber, and cinchona grow well on laterite soils.
Laterite soils are distributed across the summits of the Western Ghats (1,000–1,500 m), Eastern Ghats, Rajmahal Hills, and Malwa Plateau — covering 2.48 lakh km² (7.5% of India).
Peninsular soils are sedentary/residual soils formed in-situ from underlying bedrock and are more mature. Extra-peninsular (alluvial) soils are transported/azonal, less mature, but highly fertile.
Peaty and marshy soils are black, heavy, highly acidic, and rich in organic matter, but deficient in potash and phosphate. Major areas: Kottayam and Alappuzha (Kerala), Sundarbans (WB), and coastal Odisha and Tamil Nadu.
Saline and alkaline soils form due to poor drainage, high sub-soil water table with capillary salt rise, excess irrigation (waterlogging in Punjab/Haryana canal areas), and coastal storm surges. They cover ~68,000 km² (2.07%) of India.
India's total degraded land is 97.85 million ha (29.7% of geographical area) per the SAC/ISRO Land Degradation Atlas 2021. Desertification affects 83.69 million ha (2018–19 data).
India pledged to restore 26 million hectares of degraded land by 2030 under the Bonn Challenge/UNCCD Land Degradation Neutrality (LDN) commitment. About 18.94 million ha has already been restored.
The Soil Health Card (SHC) Scheme was launched on 19 February 2015 at Suratgarh, Rajasthan, by PM Modi. It tests 12 soil parameters every 2 years and completed its 10th anniversary in February 2025.
Temperature overrides rainfall in determining vegetation above 900 m altitude — this is why coniferous forests occur in the Himalayas despite rainfall levels that would produce broadleaf evergreen forests at lower altitudes.
Related Chapters
Peninsular Plateau
The ancient Peninsular Plateau: Central Highlands, Deccan Plateau, Western and Eastern Ghats, and major hill ranges with their economic and ecological importance.
Agriculture and Agro-Climatic Zones of India
India's agriculture — ICAR's 15 agro-climatic zones, kharif/rabi/zaid seasons, major crops (rice, wheat, millets, jute, tea, coffee, spices), irrigation types, Green Revolution legacy, and key schemes (PMKSY, PM-KISAN, e-NAM).
Rock System — Geological History of India
India's geological evolution from Archean basement rocks through Gondwana coal beds to Deccan Traps — the foundation of its mineral wealth.
Natural Vegetation of India
India's five forest types, vegetation zones by rainfall/altitude, biodiversity hotspots, Biosphere Reserves, and conservation framework.