2017 GS Paper I, all questions

UPSC Prelims 2017 · GS Paper I

Question 71: Economy and Social Development

Which of the following practices can help in water conservation in agriculture ?

  1. 1.Reduced or zero tillage of the land
  2. 2.Applying gypsum before irrigating the field
  3. 3.Allowing crop residue to remain in the field

Select the correct answer using the code given below :

a1 and 2 only
b3 only
c1 and 3 only
d1, 2 and 3

AnswerUPSC’s answer is (c).

Reduced or zero tillage leaves the soil structure intact, cuts evaporation and improves infiltration, so it conserves soil moisture. Leaving crop residue on the field acts as a mulch that shades the soil, slows evaporation and reduces runoff, which also saves water. Gypsum is applied to reclaim sodic soils and to supply calcium and sulphur; UPSC does not treat it as a water-conservation practice. Remember: no-till and residue mulching conserve moisture.

  • 1. Reduced or zero tillage retains soil moisture.
  • 2. Gypsum reclaims sodic soils; it is not a water-conservation practice.
  • 3. Residue left on the field works as mulch and cuts evaporation.

How you could have got this

  1. If you were sure statement 1 is correct, (b) goes: it leaves 1 out.

    What you needed to know: Reduced or zero tillage retains soil moisture.

  2. Then, if you were sure statement 2 is not correct, (a) and (d) go: each of them includes 2.

    What you needed to know: Gypsum reclaims sodic soils; it is not a water-conservation practice.

Only (c) is left. You didn’t need statement 3.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Wrong: it includes gypsum (2), which UPSC does not count as a water-saving practice.
  • (b) Incomplete: reduced tillage (1) also conserves water.
  • (c) Right: reduced tillage and leaving residue conserve soil water.
  • (d) Wrong: statement 2, gypsum, is not accepted as water conservation.

Worth knowing: Gypsum can improve water infiltration in sodic soils, so Statement 2 is debatable, but UPSC's key excludes it.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious questionNext question

Source: UPSC, Civil Services (Preliminary) Examination 2017, General Studies Paper I, Series A. The paper on upsc.gov.in.