Detailed Explanation:

Answer: Option 2 — Rice

Rice cultivation is the most important anthropogenic source of both methane (CH₄) and nitrous oxide (N₂O) among the given crops. Flooded rice paddies create anaerobic conditions that promote methane production by methanogenic bacteria, which is then released through the rice plants. Additionally, the heavy use of nitrogen-based fertilizers in rice cultivation leads to nitrous oxide emissions when soil microbes convert excess nitrogen that is poorly absorbed by the rice plants.

📝 Short Notes: Greenhouse Gas Emissions from Agriculture

• Methane from Rice: Waterlogged paddy fields create oxygen-depleted (anaerobic) conditions ideal for methanogenic archaea, producing CH₄ that escapes through rice plant stems and soil.
• Nitrous Oxide from Fertilizers: Nitrogen fertilizers undergo microbial processes (nitrification and denitrification) in soil, releasing N₂O, especially when applied in excess.
• Global Warming Potential: CH₄ is 28-34 times more potent than CO₂ over 100 years; N₂O is approximately 265-298 times more potent than CO₂.
• Rice vs Other Crops: Cotton, wheat, and sugarcane are primarily upland crops without prolonged flooding, producing minimal methane. Rice paddies account for ~10-12% of global methane emissions.
• Mitigation Strategies: Alternate wetting and drying (AWD), improved fertilizer management, use of slow-release fertilizers, and development of low-emission rice varieties.