What are the emissions from applying a tonne of urea on farms?

Applying one tonne of urea on a field emits about 0.73 t CO2 from the urea itself plus about 1.97 t CO2e of direct nitrous oxide, using IPCC defaults and the AR6 GWP. Adding indirect nitrous oxide takes it to about 3.35 t CO2e. Making the urea is extra.

The three parts of the field emission

• CO2 from urea: urea carries carbon that is released after application. IPCC 2006 Vol 4 Ch 11, Equation 11.13, uses 0.20 t C per t urea, which is 0.20 x 44/12 = 0.733 t CO2.
• Direct N2O: urea is 46% nitrogen, so a tonne holds 460 kg N. The IPCC 2006 default EF1 is 0.01 kg N2O-N per kg N applied (Equation 11.1). Multiply by 44/28 to get N2O.
• Indirect N2O: part of the nitrogen volatilises as ammonia and part leaches, and some of each later turns into N2O. IPCC 2006 defaults: 10% volatilised with EF4 0.01, and 30% leached with EF5 0.0075, where leaching occurs.

Choices that change the answer

• Flooded rice: the IPCC 2006 default EF1 for flooded rice fields is 0.003, not 0.01, which cuts direct N2O by 70%.
• Climate split: the 2019 Refinement gives 0.016 for wet climates and 0.005 for dry climates. Over 460 kg N that is 3.16 or 0.99 t CO2e of direct N2O at the AR6 GWP. For irrigated land in a dry region, read the notes to Table 11.1 in the Refinement before choosing.
• Leaching: drop the leaching term for dry, unirrigated land where water does not drain through the soil.
• GWP: N2O is 265 in AR5 and 273 in AR6. Use the set your inventory uses.

Whose emissions these are

For the farmer, all of it is Scope 1. For a food company buying the crop, it is part of Scope 3 Category 1, spread over the crop's yield. For a fertiliser marketer, N2O and CO2 released after use are use-phase emissions of a sold product, reported under Category 11 of the GHG Protocol Scope 3 Standard.

Emissions from producing the urea, mainly ammonia made from natural gas, are a separate cradle-to-gate figure and are not in the numbers above.

How to write it up

Show each factor with its IPCC table, the nitrogen content, the climate or crop choice and the GWP set. Report CO2 from urea and N2O as separate lines; they come from different equations and an auditor will check them separately.

Worked example: one tonne of urea, upland crop, IPCC 2006 defaults, AR6 GWP

• CO2 from urea: 1,000 kg x 0.20 x 44/12 = 733 kg CO2
• Direct N2O: 460 kg N x 0.01 x 44/28 = 7.23 kg N2O; x 273 = 1,973 kg CO2e
• Volatilisation: 460 x 0.10 x 0.01 = 0.46 kg N2O-N
• Leaching: 460 x 0.30 x 0.0075 = 1.035 kg N2O-N
• Indirect N2O: (0.46 + 1.035) x 44/28 = 2.35 kg N2O; x 273 = 641 kg CO2e
• Total: 733 + 1,973 + 641 = 3,347 kg CO2e, about 3.35 t CO2e per tonne applied

On flooded rice, direct N2O with EF1 0.003 is 460 x 0.003 x 44/28 x 273 = 592 kg CO2e instead of 1,973.

What Senseible does here

Senseible does not calculate field emissions from fertiliser; it has no urea application factor. It can read and keep fertiliser purchase invoices with quantities as evidence for the calculation.

• Fertiliser N2O calculation
• Scope 3 from paddy you buy
• Scope 1 emissions in agriculture
• AR5 or AR6 GWP values

Sources: IPCC 2006 Guidelines, Vol 4 Ch 11, Equations 11.1 and 11.13, IPCC AR6 WG1, global warming potentials, GHG Protocol Scope 3 Standard, Categories 1 and 11

Last reviewed 2026-10-16. Whether irrigated land in dry Indian regions should take the 2019 Refinement wet-climate EF1 of 0.016 needs checking against the Refinement text before relying on that case.