Daily Static Quiz Prelims Practice 2027
Option (a) is correct — Bhangar is older alluvium on higher terraces above the flood zone, coarser and often containing kankar (calcium carbonate concretions) that reduce fertility, while Khadar is newer alluvium deposited periodically by floods, finer and more fertile, found closer to river channels. Option (b) completely reverses these definitions. Option (c) is wrong — both types occur throughout the Indo-Gangetic belt based on elevation and age, not the regional split implied. Option (d) is wrong — kankar is specifically associated with Bhangar; Khadar, regularly refreshed by floods, has far less kankar accumulation.
- The self-ploughing characteristic of black soils is caused by the expansion and contraction of montmorillonite clay with changes in moisture content.
- Black soils are formed from the in-situ weathering of Deccan basalt (trap rock) and are found predominantly in the Deccan Plateau.
- Black soils are rich in iron, calcium, potassium and magnesium but deficient in nitrogen, phosphorus and organic matter.
- Black soils are best suited for cotton cultivation because their high moisture retention compensates for irregular rainfall in the Deccan.
All four statements are correct. Montmorillonite clay swells when wet and shrinks when dry, forming deep vertical cracks that cause self-ploughing. Black soils form through in-situ weathering of Deccan basalt under moderate rainfall and high temperature, concentrated across Maharashtra, MP, Gujarat, Telangana, and northern Karnataka. They are rich in iron, calcium, potassium and magnesium but deficient in nitrogen, phosphorus and humus. And cotton's deep roots exploit their high moisture retention, sustaining the crop through dry spells, making the Deccan the natural home of rain-fed cotton.
Option (b) is correctly matched — red and yellow soils occur across the Eastern Ghats, Chhattisgarh, Jharkhand, Odisha, and Telangana, consistently deficient in nitrogen, phosphorus, and humus, requiring heavy fertiliser inputs. Option (a) is wrong — laterite soils are characterised by an abundance, not deficiency, of iron and aluminium oxides, concentrated through leaching. Option (c) is wrong — arid and desert soils are deficient in organic matter and nitrogen but typically have high soluble salts, not a deficiency in calcium and magnesium, which accumulate in low-rainfall conditions. Option (d) is wrong — mountain and forest soils are acidic, deficient in lime and potash, and rich in humus, not deficient in iron or high in salinity.
Reason (R): The productivity of alluvial soils is sustained by their fine texture, good water retention, and annual replenishment with fresh mineral-rich sediment by Himalayan rivers — partially compensating for nitrogen and phosphorus deficiencies.
Both A and R are correct, and R explains A. Despite consistent nitrogen and phosphorus deficiencies, the Indo-Gangetic alluvial belt supports India's most intensive agriculture across Punjab, Haryana, UP, Bihar, and West Bengal. This paradox is resolved by the mechanisms in R: fine texture enabling capillary water retention, and annual flood deposition of fresh mineral-bearing Himalayan sediment (especially in Khadar areas) partially replenishing extracted nutrients — the direct physical explanation for sustained productivity.
Option (c) is correct — the Chambal ravines form through gully erosion, as concentrated runoff from the Chambal River and its tributaries cuts into soft alluvial and sedimentary deposits, forming steep-sided, self-reinforcing gullies that have turned roughly 4,000 sq km into badland. Option (a) is wrong — wind deflation dominates the Thar Desert further west; the Chambal region's 600–900 mm rainfall generates far more erosive surface runoff. Option (b) is wrong — sheet erosion produces gradual thinning on gentle slopes, not the dramatic incised gullies seen here. Option (d) is wrong — waterlogging from canal irrigation causes salinisation, a distinct problem in Punjab and Haryana, not the Chambal's natural fluvial erosion.
