UPSC CSE Prelims 2010
Which of the statements given above is/are correct?
Statement 1 is correct. Rice cultivation, particularly in flooded paddies, creates anaerobic (oxygen-deprived) conditions in the soil. Under these conditions, specific anaerobic microorganisms perform methanogenesis, a process that produces and releases methane (CH₄) into the atmosphere. Methane is a potent greenhouse gas with a significant Global Warming Potential (GWP), contributing to global warming.
Statement 2 is correct. The widespread use of nitrogen-based fertilizers in agriculture, including rice cultivation, can lead to the emission of nitrous oxide (N₂O) from the cultivated soil. Microbial processes such as nitrification and denitrification convert nitrogen compounds in the soil into N₂O, which is then released. Nitrous oxide is another powerful greenhouse gas with a high GWP.
Therefore, both methane emissions from anaerobic decomposition and nitrous oxide emissions from fertilizer use contribute to global warming in regions with extensive rice cultivation.
Option A (1 only) is incorrect because it overlooks the contribution of nitrous oxide emissions resulting from the use of nitrogen-based fertilizers in rice cultivation.
Option B (2 only) is incorrect because it disregards the substantial methane emissions that occur under the anaerobic conditions prevalent in flooded rice paddies.
Option D (Neither 1 nor 2) is incorrect as both statements accurately identify mechanisms through which rice cultivation contributes to the emission of greenhouse gases and, consequently, to global warming.