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Difficulty: MediumSoils, Natural Vegetation, and Agriculture in India

Regarding the pedological characteristics, chemical composition, and geographic distribution of Black Soils (Regur soils) in India, which of the following statements are correct?

  1. Black soils possess high moisture-retention capacity and develop deep cracks during the dry season, leading to self-ploughing and improved subsoil aeration.Answer
  2. These soils are chemically rich in calcium carbonate, magnesia, potash, and lime, but are notably deficient in nitrogen, phosphorus, and organic matter.Answer
  3. C
    Black soils are predominantly distributed along the high-rainfall coastal deltas of Odisha and West Bengal formed by riverine alluvial deposition.
  4. D
    The pedogenesis of Black soils is primarily driven by intense silica leaching under continuous heavy tropical rainfall.

Answer

Black soils are characterized by high moisture retention with self-ploughing properties, and are rich in lime, magnesia, and potash while deficient in nitrogen, phosphorus, and organic content.
Black soils (Regur) originate from basaltic lava in the Deccan plateau under semi-arid conditions. Their high clay content gives them excellent moisture retention and causes them to contract into deep cracks during dry spells, facilitating self-ploughing. Chemically, they are rich in iron, lime, calcium carbonate, magnesia, and potash, but deficient in nitrogen, phosphorus, and organic humus.

Step-by-Step Solution

1
Examine the physical properties and moisture dynamics of Black soils.
Determine that high montmorillonite clay content causes swelling when wet and shrinking with deep cracking when dry, creating a natural self-ploughing mechanism.
Physical weathering of basaltic lava under semi-arid conditions produces sticky, clay-rich soil horizons.
2
Analyze the chemical composition and mineral nutrients present in Regur soils.
Confirm that calcium, magnesium, iron, and potash levels are high, whereas organic matter, nitrogen, and phosphorus levels are low.
Mineral inheritance from volcanic basalt provides bases, but rapid oxidation in dry climates prevents accumulation of organic humus.
3
Evaluate statements regarding regional distribution and soil genesis against other Indian soil types.
Identify that eastern deltaic regions have Alluvial soils and high-leaching zones form Laterite soils, ruling out these statements for Black soils.
Black soil formation depends on basaltic lava bedrock across the central and western Deccan plateau.

Key Concept

Pedological features, chemical composition, and spatial distribution of Black Soils in India.
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Topics

Soils, Natural Vegetation, and Agriculture in India

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