UPSC Prelims 2019 Q41: Environment & Ecology – Pollution & Waste Management
- (a) 1 and 3 only
- (b) 2 and 3 only
- (c) 2 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Reactive Nitrogen in Agriculture: Facts
| Statement | Claim | Verdict | Detail |
|---|---|---|---|
| 1 | Agricultural soils release nitrogen oxides (NOx, N2O) | TRUE | Nitrogen fertilizer application and microbial nitrification/denitrification in soil release N2O (nitrous oxide, a potent GHG) and NOx. Agriculture is the largest anthropogenic source of N2O globally. |
| 2 | Cattle release ammonia (NH3) | TRUE | Livestock manure and urine release NH3; cattle account for the largest share of NH3 emissions from livestock. |
| 3 | Poultry releases reactive nitrogen compounds | TRUE | Poultry droppings emit NH3, N2O and other reactive N - a growing concern with intensifying poultry industry. |
All three are correct. Answer: (d) 1, 2 and 3.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statement 2 (cattle -> NH3) is also correct.
- (b) Incorrect. Statement 1 (soils -> N2O/NOx) is also correct.
- (c) Incorrect. Statements 1 and 3 are also correct.
- (d) CORRECT. All three - agricultural soils (N2O/NOx), cattle (NH3), and poultry (NH3, N2O, other reactive N) - release reactive nitrogen compounds.
Key point
Reactive N sources in agriculture: (1) Soils -> N2O/NOx from fertilizer + microbes. (2) Cattle -> NH3 from manure/urine. (3) Poultry -> NH3 + N2O + reactive N from droppings. All correct.
Remember
All three statements are correct. Agricultural soils release nitrogen oxides (NOx, N2O) from fertilizer application and microbial processes. Cattle release ammonia (NH3) from manure and urine. And the poultry industry releases reactive nitrogen compounds (NH3, N2O). Agriculture is the dominant global source of reactive nitrogen.
Common mistakes
- Assuming reactive N is only industrial - agriculture is now the dominant source.
- Ignoring N2O's 265x GWP over CO2 (100-year horizon).
- Not knowing India is a major NH3 and N2O emitter due to fertilizer use and livestock.
Exam tip
Nitrogen cascade: N2 (inert) -> NH3/NOx/N2O (reactive) via Haber-Bosch (fertilizer), combustion, biological fixation. Effects: acid rain (NOx), eutrophication (NO3-), GHG (N2O), stratospheric ozone depletion (N2O), particulate matter (NH3 -> PM2.5).
Sources
- IPCC AR6 - Working Group III (Agriculture, Forestry and Other Land Use)
- FAO - Livestock's Long Shadow report