UPSC Prelims 2020— Question 51

This question tests fertigation. The key concept is: Fertigation applies nutrients through irrigation water, improving nutrient-use efficiency and reducing losses through leaching. It can also help manage some water-quality and soil-related conditions, but the claim about efficient application of rock phosphate is not generally valid because conventional phosphatic fertilizers are poorly suited to fertigation compared with soluble forms. The accepted combination is 1, 3 and 4. The verified answer for the uploaded Set-B paper is option C. Option A — 1, 2 and 3 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Fertigation applies nutrients through irrigation water, improving nutrient-use efficiency and reducing losses through leaching. It can also help manage some water-quality and soil-related conditions, but the claim about efficient application of rock phosphate is not generally valid because conventional phosphatic fertilizers are poorly suited to fertigation compared with soluble forms. The accepted combination is 1, 3 and 4. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option B — 1, 2 and 4 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Fertigation applies nutrients through irrigation water, improving nutrient-use efficiency and reducing losses through leaching. It can also help manage some water-quality and soil-related conditions, but the claim about efficient application of rock phosphate is not generally valid because conventional phosphatic fertilizers are poorly suited to fertigation compared with soluble forms. The accepted combination is 1, 3 and 4. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option C — 1, 3 and 4 only: This is the correct option. It matches the verified conclusion because Fertigation applies nutrients through irrigation water, improving nutrient-use efficiency and reducing losses through leaching. It can also help manage some water-quality and soil-related conditions, but the claim about efficient application of rock phosphate is not generally valid because conventional phosphatic fertilizers are poorly suited to fertigation compared with soluble forms. The accepted combination is 1, 3 and 4. The wording of the option is consistent with the governing concept tested by the question. Option D — 2, 3 and 4 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Fertigation applies nutrients through irrigation water, improving nutrient-use efficiency and reducing losses through leaching. It can also help manage some water-quality and soil-related conditions, but the claim about efficient application of rock phosphate is not generally valid because conventional phosphatic fertilizers are poorly suited to fertigation compared with soluble forms. The accepted combination is 1, 3 and 4. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. For UPSC-style elimination, first identify the exact proposition being tested, then evaluate each statement independently before comparing the answer codes. Avoid treating a broad or absolute statement as correct merely because its general theme is familiar. The precise qualifiers in the question—such as 'all', 'only', 'cannot', 'largest', 'always' or a specific institutional role—often determine the answer. On that basis, option C is the verified answer.