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General Studies (Paper 1) from UPSC CSE 2013 Prelims
Subject: General Studies (Paper 1) Science and Technology Union Public Service Commission — Civil Services Examination Last updated May 9, 2026
UPSC CSE Prelims 2013 General Studies (Paper 1)

Which of the following adds/add nitrogen to the soil?

1. Excretion of urea by animals
2. Burning of coal by man
3. Death of vegetation

Select the correct answer using the codes given below:

Answer & Explanation

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Correct Answer: Option C — 1 and 3 only
The correct answer is 1 and 3 only.

1. Excretion of urea (Yes): Animal waste contains nitrogenous compounds. Soil bacteria convert this urea into ammonia and nitrates, enriching the soil.

2. Burning of coal (No): This releases nitrogen oxides into the atmosphere. It is a source of air pollution, not a direct method of soil fertilization.

3. Death of vegetation (Yes): When plants die, decomposers break down their organic matter, returning the nitrogen stored in their tissues back into the soil.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
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UPSC CSE 2013 Prelims

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Exam UPSC CSE
Stage Prelims
Year 2013
Subject General Studies (Paper 1)
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