Soils of India — Set 1

Correct Answer: D. Alluvial Soil

• **Alluvial soil** = covers ~40% of India's total land area, making it the most widespread soil type, formed by river silt from Indus, Ganga, and Brahmaputra. • **~40% of India's land area** — the extensive coverage of alluvial soil across the Indo-Gangetic plains. • 💡 Wrong-option analysis: Black soil: covers ~15% mainly in Deccan Plateau; Red soil: ~18%, mainly peninsular India; Laterite soil: high-rainfall Western/Eastern Ghats, much smaller coverage.

Correct Answer: A. Black Soil

• **Black soil (Regur soil)** = called 'Regur' from the Telugu word 'Reguda', ideal for cotton cultivation, formed from basaltic Deccan Trap rock. • **Deccan Trap region** — the volcanic basaltic rock origin of black/Regur soil covering Maharashtra, Gujarat, and MP. • 💡 Wrong-option analysis: Desert soil: sandy, alkaline, found in Rajasthan; Red soil: formed from crystalline/metamorphic rock, reddish due to iron oxide; Saline soil: high salt content, found in arid/coastal areas.

Correct Answer: B. Iron Oxide

• **Iron Oxide** = gives red soil its characteristic reddish colour due to wide diffusion of iron in crystalline and metamorphic rocks. • **Yellowish in hydrated form** — when iron is hydrated, red soil turns yellow, explaining the dual-colour classification as 'Red and Yellow soil'. • 💡 Wrong-option analysis: Magnesium: an element in black soil, not the red colour agent; Calcium Carbonate: found in Bhangar (old alluvium) as Kankar nodules; Potash: red soil is actually deficient in potash.

Correct Answer: B. Intense Leaching

• **Intense Leaching** = the key process forming laterite soil, where heavy rainfall washes away silica and lime, leaving iron and aluminum oxides. • **Iron and aluminum oxides remain** — the residue after leaching gives laterite its reddish colour and brick-like hardness. • 💡 Wrong-option analysis: Siltation: creates alluvial soil by river deposition; Wind Deposition: creates desert/arid sandy soil; Volcanic Eruption: basaltic lava creates black (Regur) soil.

Correct Answer: D. Old Alluvium

• **Bhangar = Old Alluvium** = older alluvium found above flood levels on river terraces, often containing calcareous 'Kankar' deposits. • **Kankar nodules** — calcium carbonate concretions found in Bhangar that indicate lower fertility compared to newer Khadar alluvium. • 💡 Wrong-option analysis: Deltaic soil: describes alluvial soil in deltas, not Bhangar specifically; New Alluvium: that is Khadar (the opposite of Bhangar); Sandy soil: describes desert/arid soil, not Bhangar.

Correct Answer: B. Black Soil

• **Black soil (self-ploughing capacity)** = develops deep cracks in dry season, allowing natural mixing of soil layers and better aeration — called 'self-ploughing'. • **Deep cracks in dry season** — the unique characteristic of black soil; becomes very sticky when wet and rock-hard when dry. • 💡 Wrong-option analysis: Peaty soil: forms in waterlogged areas, high organic content; Laterite soil: hard reddish soil, no self-ploughing; Mountain soil: found in Himalayan forests, varies with altitude.

Correct Answer: C. Red Laterite Soil

• **Red Laterite Soil** = most suitable for cashew nut cultivation in Tamil Nadu, Andhra Pradesh, and Kerala; responds well to fertilizers for plantation crops. • **Rich in iron, poor in organic matter** — the chemical profile of red laterite soil that suits tree crops like cashew more than grain crops. • 💡 Wrong-option analysis: Marshy soil: waterlogged, not ideal for cashew; Saline soil: high salt content, inhibits most crops; Alluvial soil: best for grains/cereals, not specifically for cashew.

Correct Answer: B. Alkaline

• **Alkaline** = desert/arid soils are alkaline due to high salt content and low rainfall that doesn't leach salts away. • **Indira Gandhi Canal area** — example where proper irrigation transformed desert soil into productive agricultural land. • 💡 Wrong-option analysis: Varies randomly: desert soil pH is consistently alkaline; Neutral: alluvial/forest soils are closer to neutral; Highly Acidic: laterite soils are acidic, not desert soils.

Correct Answer: D. Peaty Soil

• **Peaty soil** = formed under waterlogged conditions with heavy rainfall and high humidity, accumulating large amounts of dead organic matter with high humus content. • **Heavy, black, high humus** — the three key characteristics of peaty soil found in coastal humid areas. • 💡 Wrong-option analysis: Laterite soil: forms in high-rainfall areas but through leaching, not waterlogging; Red soil: forms by crystalline rock weathering, not waterlogging; Alluvial soil: deposited by rivers, not formed in waterlogged conditions.

Correct Answer: B. River floodplains

• **Khadar soil found in river floodplains** = new alluvium deposited by annual floods, fine-grained and highly fertile for intensive agriculture. • **Annual flood deposition** — Khadar is renewed almost every year, keeping it the most fertile alluvial sub-type. • 💡 Wrong-option analysis: Coastal deserts: these are arid/desert soil areas; Mountain tops: forest/mountain soils; Plateau regions: may have black or red soils, not Khadar specifically.