Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide ?
- (a) Cotton
- (b) Rice ✓ UPSC's answer
- (c) Sugarcane
- (d) Wheat
Why the answer is (b)
• Flooded paddy fields create anaerobic conditions in which methanogenic bacteria produce methane; rice cultivation is the largest crop-related source of methane, contributing roughly 10% of global agricultural emissions.
• Heavy use of nitrogen fertiliser on rice also releases nitrous oxide through nitrification and denitrification, so rice is the most important anthropogenic crop source of both gases — option (b).
• Cotton, sugarcane and wheat emit nitrous oxide from fertiliser but are grown in aerated soils and produce little methane.
• Techniques such as alternate wetting and drying and direct seeding cut rice emissions.
• Hence option (b).
Why the other options are wrong
- (a) Cotton
- Cotton is grown in aerated soil and emits little methane.
- (c) Sugarcane
- Sugarcane does not produce significant methane.
- (d) Wheat
- Wheat fields are not flooded and produce little methane.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2022, held on 5 June 2022. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.