Q90. Which process is the primary cause of laterite-soil development?
[SSC MTS (5 September 2023, Shift 2)]
- (A) Compaction
- (B) Leaching
- (C) Heat acting alone
- (D) Sedimentation
Answer: (B) Leaching
Explanation: Leaching washes silica and soluble bases downward or away during heavy rainfall. Iron and aluminium oxides become concentrated, resulting in typical lateritic materials. Heat alone cannot explain the process; the combination of weathering and abundant rainfall is essential.
Q89. Which soil is comparatively rich in sodium, potassium and magnesium salts, ranges from sandy to loamy, and occurs in western Gujarat, eastern coastal deltas and the Sundarbans?
[UPSC CDS General Knowledge (3 September 2023)]
- (A) Peaty soil
- (B) Laterite soil
- (C) Arid soil
- (D) Saline soil
Answer: (D) Saline soil
Explanation: Saline soils accumulate soluble salts where evaporation, seawater influence or inadequate drainage concentrates dissolved minerals. These occur in western Gujarat and parts of coastal eastern India. Salinity makes water uptake difficult for many crops and reduces productivity without suitable management.
Q88. Which Indian soil develops through the weathering of basalt lava?
[MP Police Constable (23 August 2023, Shift 1)]
- (A) Red soil
- (B) Alluvial soil
- (C) Laterite soil
- (D) Regur soil
Answer: (D) Regur soil
Explanation: Regur is black cotton soil produced in large part through weathering of basaltic volcanic rocks. It is characteristic of the Deccan region and is recognized by its dark colour, high clay content, pronounced dry-season cracking and water storage.
Q87. Wind-deposited soil material made mainly of silt and dust is termed what?
[SSC CHSL Tier I (14 August 2023, Shift 2)]
- (A) Loam
- (B) Marl
- (C) Loess
- (D) Podzol
Answer: (C) Loess
Explanation: Loess is a wind-blown accumulation of fine, predominantly silt-sized particles. It differs from loam, which refers to a mixed soil texture, and from podzol, which describes a characteristic leached soil profile. Wind deposits can be fertile but erosion-prone.
Q86. Which constituent explains the reddish colour commonly observed in red soils?
[HSSC CET Group C Mains, Group 56 (7 August 2023)]
- (A) Potash and magnesia
- (B) Iron compounds
- (C) Overgrazing
- (D) None of these
Answer: (B) Iron compounds
Explanation: Ferric iron oxides such as hematite impart red colours to many weathered soils. They commonly form on crystalline rocks in parts of peninsular India. The colour is a mineralogical characteristic rather than a direct result of grazing or potash content.
Q85. Red soil mainly owes its characteristic colour to which substance?
[HSSC CET Group C Mains, Group 57 (6 August 2023)]
- (A) Overgrazing
- (B) Iron oxide
- (C) Potash and magnesia
- (D) None of these
Answer: (B) Iron oxide
Explanation: Iron-bearing minerals oxidize during rock weathering and create reddish ferric oxides. This is the principal reason red soils appear red. Such soils are extensive in parts of southern and eastern peninsular India, often developed from old crystalline rocks.
Q84. Which region is the characteristic black-soil region of India?
[SSC CGL Tier I (18 July 2023, Shift 1)]
- (A) Coastal Plains
- (B) Northern Plains
- (C) Deccan Trap
- (D) Himalayas
Answer: (C) Deccan Trap
Explanation: Black soil is most strongly associated with the basaltic Deccan Trap. Long-term weathering of the volcanic material produced extensive dark, clay-rich soils. These soils are important for cotton and other crops because of their substantial moisture retention.
Q83. Which soil horizon or layer normally contains the greatest concentration of humus?
[SSC MTS 2022 Paper (19 June 2023, Shift 1)]
- (A) Weathered rock
- (B) Topsoil
- (C) Parent rock
- (D) Subsoil
Answer: (B) Topsoil
Explanation: Topsoil receives decaying leaves, roots and other organic residues that microorganisms transform into humus. It is generally the biologically active soil layer. Subsoil and parent rock contain less incorporated organic material, though actual profiles vary with vegetation and climate.
Q82. Which soil is known by the name regur?
[SSC MTS 2022 Paper (17 May 2023, Shift 3)]
- (A) Peaty soil
- (B) Alluvial soil
- (C) Laterite soil
- (D) Black soil
Answer: (D) Black soil
Explanation: The name regur refers to India’s black cotton soil, common across basalt-influenced regions of the Deccan. High clay content gives it distinctive swelling, shrinking and moisture-storage properties. These characteristics help explain its connection with cotton agriculture.
Q81. Laterite-type soil occurs in which Rajasthan district?
[RPSC Executive Officer / Revenue Officer (14 May 2023, Shift 1)]
- (A) Churu
- (B) Jodhpur
- (C) Karauli
- (D) Dungarpur
Answer: (D) Dungarpur
Explanation: Dungarpur in southern Rajasthan experiences conditions more favorable to lateritic weathering than the arid northwestern districts listed. High rainfall and long-term leaching concentrate iron and aluminium compounds. Nearby Banswara is another locality where lateritic soils are reported.
