ghg-inventory-1990-2013

5.2.6 Source-specific planned improvements
Pasture quality nationwide sampling measurements
A review by Bown et al (2013) of values of the pasture metabolisable energy
concentration and nitrogen content provided updated national estimates of pasture quality.
An independent peer review of this report concluded that New Zealand should consider
collecting more measurements before changing the values used in its national Agriculture
Inventory (Stevens, 2014).
Bown et al, (2013) had identified further improvements that could be made to sampling
pasture quality, particularly of hill country pasture grazed by non-dairy cattle, sheep and
deer, and further work to support regional disaggregation of pasture quality data.
New Zealand organised a workshop in November 2014 to bring together industry
associations and researchers. A smaller working group was formed and is due to meet in
2015 to discuss and commission a multiyear study to improve the sampling, especially
where gaps were identified by Bown et al (2013).
Emission factor lactating cattle
A three-year project to update the current estimate of the relationship between DMI and
CH 4 emissions in lactating cattle started in early 2013. The research is using the
New Zealand Agriculture Greenhouse Gas Centre ruminant methane measurement
facility purpose-built calorimeter chambers to measure the relationship between enteric
fermentation emissions and DMI. As part of the study, milk yields and nitrogen content
and partitioning of the feed will be conducted. The results will be used to improve the
estimates of CH 4 and nitrous emissions from dairy cattle.
Emission factor sheep
Enteric emissions factors for sheep are being reviewed. This will include the results of
recent trials using the respiration chambers based at New Zealand’s Agriculture
Greenhouse Gas Research Centre. Results from these trials are undergoing detailed
statistical analysis for future publishing and inclusion in the national Inventory.
5.3 Manure management (CRF 3.B)
5.3.1 Description
In 2013, emissions from the Manure management category contributed 1,219.0 kt CO 2 -e
(3.1 per cent of emissions from the Agriculture sector). Emissions from Manure
management have increased by 480.0 kt CO 2 -e (64.9 per cent) from the 1990 level of
739.0 kt CO 2 -e. Methane from Manure management from dairy cattle was identified as a
key category for New Zealand in the 2015 level and trend assessment and methane from
Manure management from sheep was identified as a key category in a trend assessment.
Livestock manure is composed principally of organic material. When the manure
decomposes in the absence of oxygen, methanogenic bacteria produce CH 4 . The amount
of CH 4 emissions is related to the amount of manure produced and the amount that
decomposes anaerobically (ie relates to how the manure is stored) (table 5.3.1). In 2013,
CH 4 emissions contributed 1129.6 kt CO 2 -e (92.7 per cent of the Manure management
category) (table 5.3.1).
The Manure management category also includes N 2 O emissions related to manure
handling before it is added to agricultural soil. The amount of N 2 O emissions depends on
the system of waste management and the duration of storage. With New Zealand’s
extensive use of all-year-round grazing systems, this sub-category contributed a relatively
small amount of N 2 O in 2013 (89.4 kt CO 2 -e, 0.2 per cent of the Agriculture sector) (table
148 New Zealand’s Greenhouse Gas Inventory 1990–2013