CDS (II) 2023 General Knowledge · Question 60 of 120

Correct — D, Saline soil. All three clues point the same way. A large proportion of sodium, potassium and magnesium is the defining chemistry of saline soils, and it is exactly why they are infertile — the salts hold water back from roots and disperse the clay, so plants cannot draw moisture even from a wet soil. A texture running from sandy to loamy is the second standard descriptor. The third clue is decisive on its own: western Gujarat, the deltas of the eastern coast and the Sunderban areas of West Bengal are the three regions always named for saline soils in India, and they share an obvious cause — they are coastal or near-coastal tracts where seawater intrudes, tidal water floods the land, or salts left by evaporation accumulate. Saline soils go by several local names, among them usar, reh, kallar and thur.

• (a)Peaty soil — Peaty soils form where heavy rainfall and high humidity let organic matter pile up faster than it decays. They are black, heavy and acidic with a very high humus content — the opposite of a salt-loaded, infertile soil — and their Indian home is the backwater country of Kerala, along with parts of coastal Odisha, Tamil Nadu and West Bengal.
• (b)Laterite soil — Laterite is the product of intense leaching under a hot climate with alternating wet and dry seasons; it is rich in iron and aluminium oxides, poor in nitrogen, lime and humus, and reddish rather than saline. It occupies the summits of the Western and Eastern Ghats and hilly parts of Karnataka, Kerala, Tamil Nadu, Madhya Pradesh, Odisha and Assam.
• (c)Arid soil — The genuinely difficult distractor, because arid soils of western Rajasthan can also be salty and sandy. They are separated by the rest of the description — arid soils are red to brown, low in humus and nitrogen, often carry a kankar layer of calcium carbonate at depth, and belong to the desert margin, not to eastern coastal deltas and the Sunderbans.

Saline and alkaline soils, sometimes called salt-affected soils, are soils in which soluble salts of sodium, potassium and magnesium have accumulated to the point of harming plants. They arise where evaporation exceeds leaching and there is nothing to wash the salts away — dry climates, poorly drained irrigated land, and coastal tracts reached by seawater or tidal flooding. They are treated rather than abandoned: gypsum is added to displace sodium from the clay, drainage is improved, and salt-tolerant crops are grown while the soil recovers.

Soil identification items work by elimination on one clue at a time, and here the geography is the strongest clue. Western Gujarat, the eastern deltas and the Sunderbans have almost nothing in common except proximity to the sea, so the answer has to be a soil whose cause is salt. That immediately clears peat, which is about organic matter, and laterite, which is about leaching in the uplands. Arid soil is the one that survives to the last round because it too can be salty and sandy — the tie-breaker is that arid soils belong to the north-western desert, not to the Bay of Bengal deltas. One printed slip is worth noting in passing: this stem reads 'on the basis of given characteristics' where the same question format in an earlier CDS paper reads 'on the basis of the given characteristics'. The missing word changes nothing about what is being asked.

• Saline soils contain a larger proportion of sodium, potassium and magnesium and are therefore infertile.
• Their structure ranges from sandy to loamy.
• They are widespread in western Gujarat, the deltas of the eastern coast and the Sunderban areas of West Bengal.
• Local names include usar, reh, kallar, rakar and thur.
• Over-irrigation without drainage in canal-irrigated tracts of Punjab, Haryana and western Uttar Pradesh has spread salinity; gypsum is the usual amendment.

• Picking arid soil because both it and saline soil can be sandy and salty. The regional list decides it.
• Confusing peaty soil, which is heavy with organic matter, with saline soil, which is heavy with salts.
• Treating salinity as a purely natural condition. Much of India's salt-affected land is the result of canal irrigation without drainage.

As an identify-the-soil item built from three characteristics, or as a soil-to-region matching row.

• practice — not a real PYQ

  Which amendment is most commonly used to reclaim saline and alkaline soils in India?

  • (a)Lime
  • (b)Gypsum
  • (c)Urea
  • (d)Rock phosphate

  Answer(b) Gypsum — it supplies calcium that displaces sodium from the clay, after which the salts can be leached away through improved drainage.

• practice — not a real PYQ

  Peaty soils in India are most characteristically found in

  • (a)western Rajasthan
  • (b)the Deccan lava plateau
  • (c)the backwater districts of Kerala
  • (d)the Chotanagpur plateau

  Answer(c) the backwater districts of Kerala — areas of heavy rainfall and high humidity where organic matter accumulates faster than it decomposes.