(a) Cotton
(b) Rice
(c) Sugarcane
(d) Wheat
1. Ans: b
Explanation:
Rice (Oryza sativa L.) is the most widely consumed staple food crop globally, holding particular significance in Asia. The production of rice is crucial for the food safety and national security of certain countries.
However, rice cultivation is also a notable source of greenhouse gas emissions, primarily methane (CH4) and nitrous oxide (N2O). Annual CH4 emissions from rice fields are estimated to contribute approximately 5-19% of global CH4 emissions. Additionally, agricultural N2O emissions surged by nearly 17% between 1990 and 2005, now accounting for 60% of global anthropogenic N2O emissions.
The flooded conditions created during rice cultivation promote anaerobic environments that favor the production of CH4 by methanogens. This CH4 can then be oxidized by methanotrophs under aerobic conditions, such as in the rhizosphere and at the soil-water interface. Ultimately, CH4 is released into the atmosphere through soil or water-atmosphere interfaces and via the rice plant’s aerenchyma.
Nitrogen fertilization and water management practices, such as alternating wetting and drying, facilitate N2O emissions through nitrification and/or denitrification processes in rice paddies. When applied correctly, fertilizer and management interventions can significantly help in controlling both CH4 and N2O emissions during rice cultivation.
Notably, different rice varieties exhibit considerable differences in total CH4 and N2O emissions. Thus, selecting rice varieties that yield lower CH4 and N2O emissions may serve as an effective strategy for mitigating greenhouse gas emissions from rice paddies.
Additional Information:
Other Methane emissions result from livestock and other agricultural practices, land use, and by the decay of organic waste in municipal solid waste landfills.
Other Nitrous oxide emissions include agricultural, land use, and industrial activities; combustion of fossil fuels and solid waste; as well as during treatment of wastewater.
Hence, option b is correct.
Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2022