Correct Option
Rice cultivation is recognized as a significant anthropogenic source of both methane (CH₄) and nitrous oxide (N₂O). Methane is primarily emitted from flooded paddy fields due to the anaerobic decomposition of organic matter by methanogenic bacteria. Nitrous oxide emissions result from the application of nitrogenous fertilizers, which undergo nitrification and denitrification processes in the soil. Both CH₄ and N₂O are potent greenhouse gases, contributing substantially to global warming.
Incorrect Options
Cotton (1) is typically cultivated under rain-fed or irrigated conditions that do not involve prolonged flooding, thus limiting anaerobic decomposition and subsequent methane emissions. While nitrogen fertilizers are used, its overall contribution to N₂O emissions is generally lower than that from rice cultivation.
Sugarcane (3) cultivation can contribute to greenhouse gas emissions, particularly N₂O from fertilizer use and CO₂ from biomass burning. However, it is not grown under continuously flooded conditions, which means its methane emissions are negligible compared to rice. Its combined emissions of CH₄ and N₂O are less significant than those from rice.
Wheat (4) is a rabi crop primarily grown in non-flooded, aerobic soil conditions. This absence of prolonged waterlogging prevents the anaerobic decomposition necessary for significant methane production. Although nitrogen fertilizers are applied, leading to some N₂O emissions, its overall contribution to both CH₄ and N₂O is considerably less than that of rice.