ghg-inventory-1990-2013

grazing livestock on pasture, range and paddock land, which is covered in the next
section (urine and dung deposited by grazing animals (CRF 3.D.1.3)).
Animal manure is not used for feed, fuel or construction in New Zealand. In accordance
with IPCC good practice guidance (IPCC, 2000), the following equations are used to
determine direct N 2 O emissions from the application of animal manure to soil. As
recommended by IPCC (2006), the adjustment for NH 3 and NO x emissions from
volatilisation is no longer applied:
44
28 ∙ ∙
Where: F AM is the total amount of animal manure nitrogen applied to soils from manure
management systems (other than pasture, range and paddock), which is derived
as a fraction of the nitrogen excretion rates, N ex , described in section 5.3.2, and,
EF 1 is the proportion of direct N 2 O emissions from nitrogen input to the soil
(0.01; table 5.5.2).
The output of the Tier 2 livestock population characterisation and feed-intake estimate
(section 5.1.3) and nitrogen excretion calculation (section 5.3.2) is used to calculate
national manure N quantities per livestock category, which are allocated per manure
management system as detailed in table 5.3.2. This ensures the same base values are used
for the N 2 O emission calculations throughout New Zealand’s Inventory. Further details
can be found in the Inventory methodology document (http://mpi.govt.nz/news-andresources/statistics-and-forecasting/greenhouse-gas-reporting/).
Because the majority of livestock manure in New Zealand is excreted directly onto
pasture, emissions from the organic N fertiliser subcategory are relatively small.
However, emissions from this source have almost doubled since 1990 due to the increase
in dairy population numbers. In 1990, manure fertiliser emissions were 78.5 kt CO 2 -e
(0.2 per cent of agricultural emissions) and in 2013 this had increased to 147.8 kt CO 2 -e
(0.4 per cent of agricultural emissions).
Urine and dung deposited by grazing animals (CRF 3.D.1.3)
The majority of livestock in New Zealand are grazed outdoors on pasture. This system is
the predominant regime for managing animal manure, with 95 per cent of dairy cattle
excreta and 100 per cent of non-dairy cattle, sheep, deer and other livestock manure
allocated to it (table 5.3.2).
In line with good practice guidance (IPCC, 2006), the following equations are used to
determine direct N 2 O emissions from grazing livestock manure:
For sheep, cattle and deer urine only, and urine and dung for all other livestock
categories:
44
28 44
28 ∙ ∙ ∙
For sheep, cattle and deer dung only:
44
28 44
28 ∙ ∙
∙
Where: N T is the population of livestock category, T (population as calculated in section
5.1.3),
Nex T is the annual average nitrogen excretion per head by each livestock
category (kg N/head/year) (section 5.3),
New Zealand’s Greenhouse Gas Inventory 1990–2013 165