Which statements best describes the main sources of nitrous oxide emissions in agriculture?

• A. Soil and manure management, fertilizer application, and microbial processes.
• B. Fertilizer application only without microbial processes.
• C. Enteric fermentation in ruminant animals only.
• D. CO2 from fossil fuel combustion.

Answer: (C)

Nitrous oxide in agriculture mainly comes from microbial nitrogen cycling in soils and manure management, driven by fertilizer application and organic nitrogen in manures. Microbes carry out nitrification and denitrification, and N2O is released as a byproduct during these processes. Enteric fermentation in ruminant animals is a major source of methane, not nitrous oxide, so it doesn’t describe the main sources of N2O. By including soil and manure management, fertilizer application, and microbial processes, the statement captures the primary pathways through which agricultural N2O is produced.