BharatNotes What is Laterite Soil?
Laterite soil is a reddish-brown, iron- and aluminium-rich tropical soil formed by intense weathering and leaching under hot, humid climates with alternating wet and dry seasons. The term was coined from the Latin later ("brick") because the soil, soft and easily cut when moist, hardens irreversibly once exposed to air — a property that has made it a traditional building material from Goa's churches to the foundations of Angkor Wat.
It is one of the eight major soil groups recognised in the Indian Council of Agricultural Research (ICAR) classification, alongside alluvial, black, red, desert, forest, peaty and saline soils.
How It Forms (Laterization)
Laterization requires heavy rainfall (often 200 cm or more) and high temperatures (roughly 20–28°C) with a pronounced dry season. The process works as follows:
- Percolating rainwater dissolves and removes silica and soluble bases (desilication / leaching).
- Iron and aluminium sesquioxides (Fe₂O₃, Al₂O₃) are left behind and concentrated in the upper soil.
- During the dry season, capillary action draws these oxides to the surface, where they oxidise and harden into a brick-like crust.
Because nutrients are leached away, the soil is acidic and intrinsically low in fertility — a key exam trap, since the red colour is sometimes mistaken for richness.
Key Features
| Property | Detail |
|---|---|
| Colour | Reddish-brown (iron oxide) |
| Dominant minerals | Iron and aluminium oxides; kaolinite, quartz |
| Reaction | Acidic, typically pH ~5.5–6.5 (ICAR-IISWC) |
| Fertility | Low in N, phosphate, potash, lime, humus |
| Texture | Coarse, porous; hardens on exposure to air |
| Coverage in India | Roughly 2.6–4.3% of geographical area (source estimates vary) |
Distribution and Crops in India
Laterite soils occur on the higher summits of the Western Ghats (Maharashtra, Karnataka, Kerala) between about 1,000–1,500 m, and across parts of the Eastern Ghats, Odisha, Tamil Nadu, Assam and Meghalaya. With manuring, liming and good drainage, they support high-value plantation crops:
- Cashew — laterite tracts of Kerala, Karnataka and Goa.
- Tea and coffee — well-drained, high-rainfall laterite zones of the Ghats.
- Rubber, coconut, arecanut and spices — Western Ghats belt.
UPSC Angle
For Prelims, remember three anchors: the laterization-by-leaching mechanism, the acidic-and-low-fertility nature, and the cashew-tea-coffee-rubber crop link. For Mains GS1, laterite illustrates how climate-driven weathering shapes regional agriculture and constrains land use, linking to soil conservation and degradation themes. Contrast it carefully with red soil (also iron-rich but formed by in-situ weathering of crystalline rock, less leached) and black/regur soil (clay-rich, moisture-retentive) to avoid the classic confused-pair errors.
Data current as of search verification, June 2026.
