ghg-inventory-1990-2013

EF 3(PR&P) has the most influence on total uncertainty, accounting for 91 per cent of the
uncertainty in total N 2 O emissions in 1990. This broad uncertainty reflects natural
variance in EF 3 due to weather, climate and soil type (by drainage classification);
however there have been no trials or uncertainty analysis on the effects of weather.
Table 5.5.9
Parameter
Proportion contribution of the nine most influential parameters on the uncertainty of New
Zealand’s total nitrous oxide emissions for 1990 and 2002
1990
Contribution to uncertainty (%)
2002
Contribution to uncertainty (%)
EF 3(PR&P) 90.8 88.0
EF 4 2.9 3.3
Sheep N ex 2.5 1.8
EF 5 2.2 2.8
Dairy cattle N ex 0.5 0.7
Frac GASM 0.5 0.5
EF 1 0.3 2.4
Non-dairy cattle N ex 0.2 0.3
Frac LEACH 0.1 0.2
Source: Kelliher et al, (2003, Table 16).
5.5.4 Source-specific QA/QC and verification
In preparation for the 2015 Inventory submission, the data for the direct soil, manure
from grazing livestock, and indirect emissions categories underwent Tier 1 and Tier 2
quality checks.
In 2008 and 2011, the Ministry for Primary Industries commissioned a report
investigating N 2 O emission factors and activity data for crops (Thomas et al, 2008;
Thomas et al, 2011). Statistics New Zealand’s Agricultural Production survey activity
data for wheat and maize was verified with the Foundation for Arable Research
production database between 1995 and 2007. Data for wheat and maize between the two
data sources was very similar.
Fertiliser sales data (year-end May 2013) received from the Fertiliser Association of
New Zealand were verified with data collected from the Agricultural Production survey
for year-end June 2011. The Agricultural Production survey data for fertiliser use in
New Zealand was 91,000 tonnes lower (approximately 25 per cent). The Fertiliser
Association of New Zealand data are used rather than the Agricultural Production survey
data, as 95 per cent of New Zealand nitrogen fertiliser is provided by two large
companies. Therefore, this information is more likely to be accurate than a survey of
some 35,000 individual farmers. There are a large number of differently named nitrogen
fertilisers and the Agricultural Production survey respondents often have difficulty filling
in the fertiliser question in the annual questionnaire. Some farmers use contract fertiliser
spreading companies (including aerial spreading), and may not have an accurate estimate
of the tonnes of fertiliser applied. The Agricultural production census and survey data
verified the long-term trend of the increasing use of synthetic fertiliser derived from urea.
Dicyandiamide data obtained from the Agricultural Production survey was verified with
data from the main supplier of DCD. This company has a 90 per cent share of the market.
Values obtained from this company were approximately 87 per cent of the reported DCD
usage data obtained from the Agricultural Production survey, indicating the values were
reasonably accurate.
Table 5.5.10 compares the New Zealand-specific values for EF 1 , and EF 3 with the 2006
IPCC default value and emission factors used by Australia. For EF 1 the New Zealand
value is the same as the IPCC default value. For EF 3 the value for cattle, poultry and
176 New Zealand’s Greenhouse Gas Inventory 1990–2013