ghg-inventory-1990-2013

Nitrification inhibitor dicyandiamide (DCD) 31
A methodology to incorporate the N 2 O mitigation technology, the nitrification
inhibitor dicyandiamide (DCD) into the Agriculture sector of the Inventory has been
developed. A detailed description of the methodology can be found in Clough et al
(2008). The N 2 O emissions reported in the Agricultural soils category take into account
the use of nitrification inhibitors on dairy farms using the methodology described in
Clough et al (2008).
Dicyandiamide has been well researched and the research to date has shown that it
reduces N 2 O emissions and nitrate leaching in pastoral grassland systems grazed by
ruminant animals. There have been over 28 peer-reviewed and published New Zealand
studies on its use and effects.
The method to incorporate inhibitor mitigation of N 2 O emissions into New Zealand’s
Agriculture Inventory is by an amendment to the existing IPCC methodology. Activity
data on livestock numbers is drawn from Statistics New Zealand’s Agricultural
Production survey. This survey has recently included questions on the area that DCD was
applied on grazed pastures.
The inhibitor is applied to pastures based on research that has identified good
management practice to maximise N 2 O emission reductions. This is at a rate of
10 kilograms per hectare, applied twice per year in autumn and early spring within seven
days of the application of animal excreta. ‘Good practice’ application methods of DCD
can be by slurry or DCD-coated granule.
Changes to the emission factors EF 3PR&P and parameter Frac LEACH were established
through research (table 5.5.4). These emission factors and parameters were modified
based on comprehensive field-based research that showed significant reductions in direct
and indirect N 2 O emissions and nitrate leaching where the DCD was applied. The peerreviewed
literature on inhibitor use in grazed pasture systems was reviewed and it was
determined that, on a national basis, reductions in EF 3PR&P and Frac LEACH of, 67 per cent
and 53 per cent could be made respectively (Clough et al, 2008). There has been some
research into the effect of the inhibitor on EF 3(PR&P DUNG) , however, these data are limited
and further work needs to be carried out before incorporating this research into the
New Zealand Inventory.
The reductions in the emission factors and parameters are used along with the fraction of
dairy land treated with the inhibitor to calculate DCD weighting factors.
1 %
100
∙
The appropriate weighting factor is then used as an additional multiplier in the current
methodology for calculating indirect and direct emissions of N 2 O from grazed pastures.
The calculations use a modified EF 3(PR&P) of 0.0099 and Frac LEACH of 0.0696 for dairy
grazing area in the months that the inhibitor is applied (May to September). The modified
emission factors (table 5.5.7) are based on information from the Agricultural Production
census that 2.9 per cent of the effective dairying area in New Zealand received inhibitor
in 2012.
Mitigation estimates for calendar years 2007 to 2012 are shown in table 5.5.7.
Application of this inhibitor was found to have no effect on ammonia volatilisation during
May to September when it is applied. This is supported by the results of field studies
(Clough et al, 2008; Sherlock et al, 2008).
31
After 2012, there was a voluntary suspension of DCD sales in New Zealand, so no mitigation
estimates are reported for 2013.
174 New Zealand’s Greenhouse Gas Inventory 1990–2013