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📌 The Question:

Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide?

(a) Cotton
(b) Rice
(c) Sugarcane
(d) Wheat

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✅ Correct Answer: (b) Rice

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🧠 Classroom Explanation:

Rice cultivation, particularly in flooded paddy fields, is a major anthropogenic source of both methane (CH₄) and nitrous oxide (N₂O).

• Methane (CH₄):
Flooded paddy soils create anaerobic conditions, which promote methanogenic bacteria. These microbes decompose organic matter and release methane.

• Nitrous Oxide (N₂O):
Application of nitrogen-based fertilizers leads to nitrification and denitrification processes in soil, producing nitrous oxide.

• Plant-mediated transport:
Rice plants act as biological chimneys, allowing CH₄ and N₂O to move from soil into the atmosphere through their aerenchyma tissues.

Hence, rice is the single most important crop emitting both gases together.

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🔍 Curiosity Raiser:
Did you know that dryland crops emit almost no methane, but the moment you flood a field, invisible climate chemistry begins beneath your feet?

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📚 Enrich Notes (UPSC Edge):

• Methane is ~80 times more potent than CO₂ over a 20-year period
• Nitrous oxide is ~273 times more potent than CO₂ over 100 years
• Rice fields contribute ~10–12% of global anthropogenic methane emissions
• Climate-smart alternatives include:
– Alternate Wetting and Drying (AWD)
– Direct Seeded Rice (DSR)
– Use of biochar and nitrification inhibitors
• This topic links GS-III (Agriculture + Climate Change) and Environment Prelims

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🪶 IAS Monk Whisper:
When water stands still on earth, the air starts to warm in silence.