Does drip irrigation remove the leaching term when I work out indirect nitrous oxide from fertiliser under the Intergovernmental Panel on Climate Change method?

The Intergovernmental Panel on Climate Change (IPCC) 2006 note to Table 11.3 applies the 0.30 leaching fraction where rain minus evaporation exceeds soil water holding capacity, or where irrigation other than drip is used. Elsewhere the default is zero. Drip alone may therefore drop the leaching line; that is a reading of the note.

What the note says

• FracLEACH-(H) is the fraction of nitrogen lost by leaching and runoff for regions where the sum of rain in the rainy season minus potential evaporation in the same period is greater than soil water holding capacity, or where irrigation, except drip irrigation, is used. The default is 0.30, with a range of 0.1 to 0.8.
• For other regions the default FracLEACH is taken as zero.
• The rainy season can be taken as the period when rainfall is more than 0.5 times pan evaporation.
• EF5, the share of leached nitrogen that becomes nitrous oxide (N2O) nitrogen, is 0.0075.

How this reads for drip fields

This is my reading of the note. It excludes drip irrigation from the irrigation test. It does not say what happens to a drip field in a high-rainfall district. Reading it literally, a field with only drip irrigation and a dry enough climate falls under "other regions", so the leaching term is zero. A drip field where monsoon rain still exceeds the soil's capacity stays in. The fertiliser nitrous oxide calculation answer says to apply the leaching term where water moves through the soil, such as irrigated or high-rainfall fields; this note adds the drip exclusion. Check your own rainfall and evaporation before dropping the line, and write down the choice.

What drip does not change

• The ammonia route still applies: 10% of synthetic nitrogen is assumed volatilised, and 20% of organic nitrogen, each at 0.010.
• Direct nitrous oxide from the nitrogen applied is unchanged by the leaching test.
• Equation 11.10 adds crop residue nitrogen and other inputs to the leaching term only where it applies.

100 kilograms (kg) of synthetic nitrogen per hectare, with and without the leaching line

• Ammonia route: 100 x 0.10 x 0.010 = 0.100 kg N2O nitrogen
• Leaching route: 100 x 0.30 x 0.0075 = 0.225 kg N2O nitrogen
• With both: 0.325 x 44/28 = 0.511 kg N2O x 273 = about 139.4 kg carbon dioxide equivalent (CO2e)
• Ammonia route only: 0.100 x 44/28 x 273 = about 42.9 kg CO2e
• Difference: about 96.5 kg CO2e per hectare

The 100 kg of nitrogen is an example value. 273 is the Sixth Assessment Report (AR6) 100-year warming potential for N2O. Direct nitrous oxide is not shown.

What Senseible does here

Senseible reads fuel invoices and electricity bills into emission records, so diesel for tractors and power for irrigation pumps show up once uploaded. The fertiliser, residue and field figures on this page come from your own farm records.

• Fertiliser nitrous oxide calculation
• Drip irrigation energy saving per acre
• Emissions from applying a tonne of urea

Sources: IPCC 2006 Guidelines, Volume 4, Chapter 11, Equations 11.9 and 11.10 and Table 11.3 with its note, IPCC Sixth Assessment Report, Working Group I, Chapter 7, Table 7.15 (100-year global warming potential: methane of non-fossil origin 27.0, nitrous oxide 273)

Last reviewed 2026-11-05. Based on the 2006 note. Confirm the climate test with local rainfall and pan evaporation, and follow your buyer or verifier if they fix the choice.