Previous Year Question

Paddy Fields are among the important agricultural sources of Methane (CH₄) emissions. In conventional rice cultivation, fields remain Waterlogged for extended periods, reducing the availability of oxygen within the soil. Under these conditions, Anaerobic Microorganisms decompose organic matter and produce Methane gas. Methane is a powerful Greenhouse Gas that contributes to Global Warming by trapping heat in the atmosphere.

The biological process responsible for methane production is called Methanogenesis. This process primarily occurs through Methanogenic Archaea under oxygen-free conditions. Crop Residues, Root Exudates, and other organic materials present in paddy fields provide the carbon required by these microorganisms. They produce methane by utilizing substances such as Carbon Dioxide (CO₂) and Hydrogen (H₂), or Acetate. Thus, anaerobic decomposition of organic matter in waterlogged soils is the primary cause of methane emissions.

Methane produced in paddy fields reaches the atmosphere mainly through the Aerenchyma Tissue of rice plants. Additionally, some methane escapes through Diffusion in water and as gas bubbles through a process called Ebullition. The quantity of methane emitted depends on soil temperature, duration of flooding, availability of organic matter, and agricultural management practices. To reduce methane emissions, the Alternate Wetting and Drying (AWD) technique is adopted, in which fields are periodically dried and re-irrigated under controlled conditions instead of remaining continuously flooded.

Among the other options, Wheat, Cotton, and Groundnut are generally cultivated in soils with sufficient aeration and drainage. Under normal conditions, their fields do not develop the extensive anaerobic conditions commonly found in flooded paddy fields. Therefore, they are not such significant sources of methane emissions. However, methane emissions can also occur in soils growing other crops when waterlogging develops. Methane production in rice cultivation is primarily associated with oxygen-deficient conditions in flooded soils and microbial activity, rather than the rice crop itself.