Soils, natural vegetation & agriculture
Indian soil classification (ICAR), natural vegetation belts, and the geography of agriculture and cropping seasons for UPSC GS-1.
The ICAR Soil Taxonomy
The Indian Council of Agricultural Research (ICAR), following the All-India Soil Survey (1956) and the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP, Nagpur, established 1976), classifies Indian soils into eight major groups. UPSC tests the distribution, parent material, and crop suitability of each.
Alluvial soils cover roughly 40% of India's land area and the entire Indo-Gangetic-Brahmaputra plain plus the coastal deltas. They are the most fertile, rich in potash and lime but deficient in nitrogen and phosphorus. The distinction between khadar (newer, lighter, flood-renewed alluvium) and bhangar (older, darker, lime-nodule-bearing kankar alluvium on terraces) is a recurring Prelims point.
Black soils (regur, or black cotton soil) derive from the weathering of Deccan Trap basalt laid down during the Cretaceous-Eocene (around 66 million years ago). They cover Maharashtra, western Madhya Pradesh, Gujarat, and the Malwa plateau. Rich in iron, magnesium, lime, and alumina but poor in nitrogen and phosphorus, they are moisture-retentive and self-ploughing (they crack when dry), making them ideal for cotton.
Red and yellow soils develop on crystalline igneous rock under low rainfall in the eastern and southern Deccan, Odisha, Chhattisgarh, and the Tamil Nadu hills. Their red colour comes from ferric oxide diffusion; they are porous and low in fertility unless fertilised.
Laterite, Arid and Other Soils
Laterite soils form by intense leaching under high temperature and heavy seasonal rainfall (the alternating wet-dry monsoon climate) in the Western Ghats, Eastern Ghats, Rajmahal hills, and parts of Kerala, Karnataka, and the northeast. Leaching removes silica and leaves iron and aluminium oxides; the soil hardens irreversibly on exposure (used as building brick — the name derives from Latin later, brick). Cashew, tea, and coffee thrive here.
Arid and desert soils of western Rajasthan and the Rann are sandy, saline, low in humus and nitrogen, with a high salt content and kankar layers restricting infiltration.
Saline and alkaline soils (reh, kallar, usar) result from waterlogging and over-irrigation in Punjab, Haryana, and the western Gangetic plain — a direct consequence of Green Revolution canal irrigation. Peaty and marshy soils occur in Kerala's Kuttanad, the Sundarbans, and coastal Odisha. Forest soils vary with altitude on the Himalayan slopes.
Soil degradation is a high-yield current-affairs link: the Desertification and Land Degradation Atlas of India (ISRO/SAC) reports nearly 30% of India's geographical area is degraded, and India hosted UNCCD COP14 in 2019 at Greater Noida, pledging to restore 26 million hectares by 2030.