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Chapter 6: Agriculture
6.1 Sector overview
The agriculture sector emissions totalled 36,856.64Gg CO2 equivalent and represented 49.2% of all greenhouse gas emissions in 2002. Emissions in this sector are now 15.5% higher than the 1990 baseline value of 31,911.15Gg CO2 equivalent (Figure 6.1.1). The increase is attributable to a 10.4% increase in CH4 emissions from enteric fermentation and a 27.6% increase in N2O emissions from the agricultural soils category. Prescribed burning of savanna (grasslands) has been included for the first time in the 2002 inventory. Emissions from savanna burning are a minor source of emissions (1.0Gg CO2 equivalent) but have decreased 70.2% from the 1990 level.
Emissions of CH4 from enteric fermentation dominate the sector producing 64.0% of CO2 equivalent emissions (Figure 6.1.2). Emissions of N2O are the other large component with N2O emissions from agricultural soils comprising 34.2% of emissions.
Agriculture is the principal industry of New Zealand and agricultural products are the predominant component of exports. This is due to several factors: the favourable temperate climate, the abundance of agricultural land and the unique farming practices used in New Zealand. These practices include the extensive use of all year round grazing systems and a reliance on nitrogen fixation by legumes rather than nitrogen fertilizer.
Since 1984, there have been changes in the balance of livestock species. There has been a trend for increased dairy production and deer numbers for meat and velvet production due to the prevailing good world prices. This has been counterbalanced by land coming out of sheep production and consequently decreased sheep numbers. Beef numbers have remained relatively static. There have also been productivity increases across all major animal species and classes. At the same time there has been an expansion of the land used for plantation forestry. The land area used for horticulture has not changed significantly since 1990 although the types of produce grown have changed with less grain but more vegetables, fruit and grapes for wine production.
New Zealand uses a June year for all animal statistics and reports a rolling three year average in the inventory. The June year reflects the natural biological cycle for animals in the southern hemisphere. To maintain consistency, a single livestock population characterisation is used as the framework for estimating CH4 emissions from enteric fermentation, CH4 and N2O emissions from manure management and N2O emissions from animal production. A complete time-series of the agriculture data are shown in the tables accompanying this chapter and information on livestock population census and survey procedures is included in Annex 3A.
6.2 Enteric Fermentation (CRF 4A)
6.2.1 Description
In 2002, emissions from enteric fermentation comprised 23,584.68Gg CO2 equivalent. This represents 31.5% of New Zealand's total CO2 equivalent emissions. The category is dominated by emissions from cattle which represent 57.9% of emissions from enteric fermentation. The current level of emissions from enteric fermentation is 10.4% above the 1990 level, however there have been large changes within the category. The largest increase has been in emissions from dairy cattle which have increased 65.6% since 1990. This increase has been offset by decreases in emissions from sheep (-15.6%), goats (-84.7%) horses (-20.1%) and swine (-13.1%).
CH4 is produced as a by-product of digestion in ruminants e.g. cattle and some non-ruminant animals such as swine and horses. Ruminants are the largest source of CH4 as they are able to digest cellulose. The amount of CH4 released depends on the type, age and weight of the animal, the quality and quantity of feed and the energy expenditure of the animal (IPCC, 1996).
CH4 emissions from enteric fermentation have been identified as the largest key source category for New Zealand, comprising 31.5% of the level assessment and 18.1% of the trend assessment (Tables 1.5.2 and 1.5.3). In accordance with good practice (IPCC, 2000), the methodology for estimating CH4 emissions from enteric fermentation in domestic livestock was revised to a Tier 2 methodology for the 2001 inventory.
6.2.2 Methodological issues
New Zealand's methodology uses a detailed livestock population characterisation and livestock productivity data to calculate feed intake for the four largest categories in the New Zealand ruminant population (dairy cattle, beef cattle, sheep and deer). The amount of CH4 emitted is calculated using CH4 emissions per unit of feed intake. As with any modelling approach, some assumptions are necessary to fill data gaps. These are explained in the full description of the Tier 2 approach included in Annex 3A and Clark et al.(2003). For the 2002 inventory, there are only minor revisions to the calculations. These included the updating of provisional animal statistics reported in the 2001 inventory, recalculating the three year average populations and minor corrections to calculation algorithms.
6.2.3 Uncertainties and time-series consistency
Animal numbers
Many of the calculations in this sector require livestock numbers. Both census and survey methods are used with surveys occurring in the intervening years between each census. Detailed information from Statistics New Zealand on the census and survey methods is included in Annex 3A.2.
Methane emissions from enteric fermentation
In the 2001 inventory, the CH4 emissions data from domestic livestock in 1990 and 2001 were subjected to Monte Carlo analysis using the software package @RISK to determine the uncertainty of the estimate (Clark et al., 2003; Table 6.2.1). For 2002, the Monte Carlo numerical simulation was corroborated by analytical (that is, by the calculus) solution of an equation that captured the inventory calculation. For the 2002 inventory, compared with 2001, there are only minor changes to population data and no changes to the underlying probability distribution functions. The 95% confidence interval is calculated using the standard deviation and mean values. The mean values are the reported CH4 emissions. For 1990-2002, the standard deviation divided by the mean was equal to 0.27.
Table 6.2.1. Enteric methane emissions 1990 and 2001 and the 95% confidence interval (± 1.96 standard deviations from the mean) estimated using Monte Carlo simulation
| Year | Enteric CH4 emissions (Gg/annum) | 95% CI Min | 95% CI Max |
|---|---|---|---|
1990 |
1,015.5 |
478.1 |
1,552.9 |
2001 |
1,099.4 |
517.6 |
1,681.2 |
2002 |
1,123.1 |
528.8 |
1,717.4 |
Note: The methane emissions used in the Monte Carlo analysis exclude those from swine and horses.
The uncertainty is dominated by variance in the measurements used to determine the 'CH4 per unit of intake' factor. For the measurements made of this factor, the standard deviation divided by the mean is equal to 0.26. This uncertainty is thought to be mostly natural variation from one animal to the next. Uncertainties in the estimation of energy requirements, herbage quality and population data are thought to be much smaller (0.005 - 0.05), so these variables play a much smaller role.
6.2.4 Source-specific QA/QC and verification
CH4 emission rates measured for 20 selected dairy cows scaled up to a herd have been corroborated using micrometeorological techniques. Laubach and Kelliher (in press) used the integrated horizontal flux (IHF) technique and the flux gradient technique to measure CH4 flux above a dairy herd. Both techniques are comparable, within estimated errors, to scaled-up animal emissions. The emissions from the cows measured by IHF and averaged over 3 campaigns are 329 (±153) g CH4/day/cow compared to 365 (± 61) g CH4/day/cow for the scaled-up measurements reported by Waghorn et al. (2002) and Waghorn et al. (2003).
6.2.5 Source-specific recalculations
The 2001 data are recalculated using final rather than provisional animal numbers in the three year average. This increases the level of emissions reported in 2001 (Chapter 9).
6.2.6 Source-specific planned improvements
A national inter-institutional ruminant CH4 expert group was formed to identify the key strategic directions for research into the CH4 inventory and mitigation to maximise the benefit of the existing programmes, and to develop a collaborative approach to improve the certainty of CH4 emissions. This is funded through the MAF. A private sector funded Pastoral Greenhouse Gas Research Consortium has been established to carry out research primarily into mitigation technologies and management practices but also on-farm inventory considerations. The implementation of the Tier 2 approach for enteric CH4 emissions is a consequence of the research conducted by the expert group.
6.3 Manure Management (CRF 4B)
6.3.1 Description
CH4 and N2O are produced during the anaerobic decomposition and storage of manure. Emissions from the manure management category comprised 1.7% of emissions from the agriculture sector.
Livestock manure is composed principally of organic material. When the manure decomposes in the absence of oxygen, methanogenic bacteria produce CH4. The emissions of CH4 are related to the amount of manure produced and the amount that decomposes anaerobically. CH4 from manure management has been identified as a key source category for New Zealand in the 2002 level and trend assessments (Tables 1.5.2 and 1.5.3).
This category also includes emissions of N2O related to manure handling before the manure is added to the soil. The amount of N2O released 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 category is relatively small at 75.33Gg CO2 equivalent of N2O in 2002. In comparison, agricultural soil emissions of N2O totalled 12,617.71Gg CO2 equivalent.
6.3.2 Methodological issues
Methane
Estimates of CH4 emissions from manure management for cattle, sheep and goats are derived from Joblin and Waghorn (1994). Joblin and Waghorn used stock numbers, feed intake and digestibility data from Ulyatt (1992) to estimate total faecal output from cattle, sheep, goats and deer at approximately 16 million tonnes dry weight in 1990. The same emission factors are used for each year of the inventory (Table 6.3.1).
Table 6.3.1 Derivation of New Zealand emission factors for CH4 emissions from manure
| Animal class | Faecal dry matter (1000 t) | Estimated maximum CH4 potential (1000 t) | Emissions factor (kg/animal/year) |
|---|---|---|---|
Dairy cattle |
2683.6 |
3.1 |
0.889 |
Non-dairy cattle |
3647.5 |
4.2 |
0.909 |
Sheep |
9009.1 |
10.3 |
0.178 |
Goats |
115.4 |
0.1 |
0.119 |
Deer |
313.5 |
0.4 |
0.369 |
Total |
15769.1 |
New Zealand specific methodology/emissions factors are not available for CH4 emissions from manure management for swine, horses and poultry, but emission estimates using IPCC default emission factors are included. These estimates are considered preliminary and will undergo change if New Zealand specific emission factors are derived.
Nitrous oxide
For the N2O calculation six alternative regimes for treating animal manure, known as animal waste management systems (AWMS), are identified in the IPCC Guidelines (1996). With the exception of dairy cattle, animals are allocated to the different AWMS according to the information provided in the IPCC 1996 guidelines for the Oceania region. For dairy cattle, New Zealand specific data from Haynes and Williams (1993) are used. Animals are allocated to four AWMS: (1) anaerobic lagoons, (2) pasture, range and paddock, (3) solid storage and dry-lot and (4) other systems.
The pasture, range and paddock AWMS is the predominant regime for animal waste in New Zealand as 100% of sheep, goats, deer and non-dairy cattle are allocated to it and 89% of dairy cattle. Emissions from the pasture, range and paddock AWMS are reported in the agricultural soils category.
Excretion of nitrogen for each AWMS is calculated in the worksheets accompanying this sector. A time-series of Nex values used for calculating animal production N2O emissions is also shown in the worksheets. These parameters have been derived by using the nutrient input/output model OVERSEER® to determine the annual quantities of nitrogen deposited in excreta by grazing animals. The OVERSEER® model uses feed intake from the Tier 2 model used to determine CH4 emissions (Clark et al., 2003) and an assessment of feed nitrogen content.
6.3.3 Uncertainties and time-series consistency
CH4 estimates from the anaerobic degradation of animal waste are still preliminary and are based on the maximum potential emission of CH4 from animal waste. Actual emissions are likely to be substantially lower in a ranging from 10 to 50% of the reported values with an uncertainty between 50 and 90% (Joblin and Waghorn, 1994).
Emission factors from manure and manure management systems, the livestock population, nitrogen excretion rates and the usage of the various manure management systems are the main factors causing uncertainty in N2O emissions from manure management (IPCC, 2000). New Zealand uses the IPCC default values for EF3 (direct emissions from waste) which have uncertainties of -50% to +100% (IPCC, 2000), but uses a detailed livestock characterisation and New Zealand specific nitrogen excretion rates.
N2O emissions from manure management are not a key source category for New Zealand. In contrast, uncertainties in N2O emissions from the agricultural soils category are a key source category and have been assessed using Monte Carlo simulation. The results of the simulation are discussed in the "agricultural soils" category.
6.3.4 Source-specific QA/QC and verification
CH4 emissions from manure management was identified as a key source category for New Zealand in the 2001 inventory. In preparation of the 2002 inventory, the data for this category underwent a Tier 1 QC checklist (refer Annex 6 for examples).
6.3.5 Source-specific recalculations
There are no recalculations for this category in the 2002 inventory.
6.3.6 Source-specific planned improvements, if applicable
Research has been undertaken on improving the estimate of CH4 emissions from manure (Saggar et al., 2003). Results from the research will be reviewed and incorporated in New Zealand's inventory for 2003.
6.4 Rice cultivation (CRF 4C)
6.4.1 Description
There is no rice cultivation in New Zealand.
6.5 Agricultural soils (CRF 4D)
6.5.1 Description
The agricultural soils category is the source of most N2O emissions in New Zealand comprising 12,617.71Gg CO2 equivalent in 2002. Emissions are 27.6% over the level in 1990. The category comprises three sub-categories:
- direct emissions from animal production (inputs from grazing animals)
- indirect N2O from nitrogen lost from the field as NOx or NH3
- direct N2O emissions from agricultural soils as a result of adding nitrogen in the form of synthetic fertilisers, animal waste, biological fixation, inputs from crop residues and sewage sludge.
All three of these sub-categories have been identified as key sources for New Zealand (Tables 1.5.2 and 1.5.3). Direct soil emissions from animal production is the fourth largest key source category comprising 7255.24Gg CO2 equivalent, indirect N2O from nitrogen used in agriculture comprised 3258.01Gg CO2 equivalent and direct N2O emissions from agricultural soils comprised 2104.46Gg CO2 equivalent.
Agricultural soils may also emit or remove CO2 and CH4 (IPCC, 1996). CO2 emissions from organic, mineral and limed soils are included in the LUCF sector.
6.5.2 Methodological issues
N2O emissions are determined using the IPCC 1996 approach where emission factors dictate the fraction of nitrogen deposited on the soils that is emitted into the atmosphere as N2O. The two main inputs are nitrogen fertiliser and the excreta deposited during animal grazing.
The worksheets for this chapter list the emission factors and other parameters used in the calculations. These are IPCC factors and parameters unless otherwise indicated. In particular, two New Zealand specific factors/parameters are used: EF3(PR&P) and FracLEACH. These factors were extensively reviewed for the 2001 submission, and a new value for FracLEACH was used from the 2001 inventory onwards and back-calculated to1990.
Animal production (N2O)
Direct soil emissions from animal production refers to the N2O produced from the pasture, range and paddock AWMS. This AWMS is the predominant regime for animal waste in New Zealand as 89% of dairy cattle and 100% of sheep, goats, deer and non-dairy cattle are allocated to it. Grazing animal excreta dominates the nitrogen input to pastoral soils. The emissions calculation is based on the livestock population multiplied by nitrogen excretion (Nex) values and the percentage of the population on the pasture, range and paddock AWMS. The Nex and allocation to AWMS are discussed under the manure management category of the inventory. The Nex values have been calculated using the model OVERSEER based on animal intake values used for calculating CH4 emissions for the different animal classes and species. This ensures that the same base values are used for both CH4 and N2O emission calculations.
Indirect N2O from nitrogen used in agriculture
Nitrogen fertiliser use is determined by the Zealand Fertiliser Manufacturers' Research Association (FertResearch) from sales records for 1990 to 2003. A rolling three year average is used to calculate inventory data. There has been a five fold increase in nitrogen fertiliser use over the 12 years, from 57,541 tonnes in 1990 to 289,716 tonnes reported in 2002. The N2O that is emitted indirectly through synthetic fertilizer and animal waste being spread on agricultural soils is shown in the worksheets accompanying this sector. Some of the nitrogen contained in these compounds is emitted into the atmosphere as ammonia (NH3) and NOx through volatilisation, which returns to the ground during rainfall and is then re-emitted as N2O. Emission factors are applied to the amounts of nitrogen that volatilise from synthetic fertilizer and waste.
The N2O emitted indirectly from nitrogen lost from agricultural soils through leaching and run-off is shown in Table 5 of the worksheets. This nitrogen enters water systems and eventually the sea with quantities of N2O being emitted along the way. The amount of nitrogen that leaches is taken as a fraction that is deposited or spread on land (FracLEACH).
Research studies in New Zealand together with a literature review have shown lower rates of nitrogen leaching than is suggested in the IPCC guidelines. In inventories reported prior to 2003, a New Zealand parameter for FracLEACH of 0.15 was used. However, analysis using the OVERSEER® nutrient budgeting model calibrated against four large scale, multi-year animal grazing trials indicated that a value of 0.07 for FracLEACH more closely followed actual field emissions (Thomas et al., 2002). A value of 0.07 for FracLEACH was adopted and used for all years.
Direct N2O emissions from agricultural soils
Direct emissions from agricultural soils are calculated in the five tables of worksheet 4.5. The emissions arise from synthetic fertilizer use (SN), spreading animal waste as fertilizer (AW), nitrogen fixing in soils by crops (BW) and decomposition of crop residues left on fields (CR). All of the nitrogen inputs are collected together and an emissions factor applied to calculate total direct emissions from non-organic soils.
The FAW calculation for animal waste includes all manure that is spread on agricultural soils irrespective of which AWMS it was initially stored in. This includes all waste in New Zealand except for emissions from the pasture range and paddock AWMS. No animals are reported for daily spread AWMS as advised by the IPCC guidelines. The rates of nitrogen excretion per animal for dairy cattle, non-dairy cattle, sheep and deer are derived from the OVERSEER® model as described previously. The values used for goats and poultry are unchanged from previous submissions. An emissions factor (EF3) of 0.01 is applied to the excretion value (Carran et al., 1995; Muller et al., 1995; de Klein et al., 2003; Kelliher et al., 2003).
Direct N2O emissions from organic soils are calculated by multiplying the area of cultivated organic soils by the IPCC default emissions factor (Table 2 of worksheet 4.5). Recent analysis identified 202,181 hectares of organic soils of which it is estimated that 5% (i.e. 10,109 ha) are cultivated on an annual basis (Kelliher et al., 2003). The IPCC default emissions factor (EF2 equal to 8) is used for all years of the time-series. Prior to the 2001 inventory, there was a revision of the area of cultivated soils as the previous estimate was based on a survey undertaken in 1970. The previous survey reflected the total amount of peat soil, not cultivation.
6.5.3 Uncertainties and time-series consistency
Uncertainties in N2O emissions from agricultural soils are assessed for the 1990 and 2002 inventory using a Monte Carlo simulation of 5000 scenarios with the @RISK software (Kelliher et al., 2003). The emissions distributions are strongly skewed reflecting that of pastoral soil drainage whereby 74 % of soils are classified as well-drained, while only 9 % are classified as poorly drained.
The Monte Carlo numerical assessment was also used to determine the effects of variability in the nine most influential parameters on uncertainty of the calculated N2O emissions in 1990 and 2001. These parameters are shown in Table 6.5.2 together with their percentage contributions to the uncertainty. There was no recalculation of the influence of parameters for the 2002 inventory. The Monte Carlo analysis confirmed that uncertainty in parameter EF3, the emissions factor for excreta N deposited during grazing, has the most influence on total uncertainty accounting for 91 % of the uncertainty in total N2O emissions in 1990. This broad uncertainty reflects natural variance in EF3 determined largely by the vagaries of the weather and soil type.
Table 6.5.1 Uncertainties in N2O emissions from agricultural soils for 1990 and 2002 estimated using Monte Carlo simulation
| Year | N2O emissions from agricultural soils (Gg/annum) | 95% CI Min | 95% CI Max |
|---|---|---|---|
1990 |
31.9 |
17.2 |
58.2 |
2002 |
40.6 |
23.4 |
70.4 |
Table 6.5.2 Percentage contribution of the nine most influential parameters on the uncertainty of total N2O emissions inventories for 1990 and 2001
6.5.4 Source-specific QA/QC and verification
The nitrogen fertiliser data obtained from FertResearch are corroborated by the MAF using urea production figures and industrial applications (including resin manufacture for timber processing) data.
Field studies to establish a better quantification of EF3 have been performed as part of a collaborative research effort called NzOnet [The research conducted by NzOnet is funded by the MAF. NzOnet draws on the skills of researchers in Crown Research Institutes and universities, and includes researchers from the private sector. NzOnet is also supported by the NZCCO.] . NzOnet researchers in the Waikato (Hamilton), Canterbury (Lincoln) and Otago (Invermay) have measured EF3 for pastoral soils of different drainage class (de Klein et al., 2003). Kelliher et al. (2003) assessed all available EF3 data and its distribution with respect to pastoral soil drainage class to determine an appropriate national, annual mean value. The research and analysis indicate that if excreta is separated into urine and dung, EF3 could be set to 0.007 for urine and 0.003 for dung. However, it is recognised that the dung EF3 data are limited. Combining urine and dung EF3 values, the dairy cattle total excreta EF3 is 0.006. In comparison, the current New Zealand specific value is 0.01 and the IPCC default value is 0.02. Although the current data suggest that a reduction may be appropriate, the on-going studies do not yet provide sufficient evidence to change EF3 from the New Zealand specific value of 0.01 (Kelliher et al., 2003).
6.5.5 Source-specific recalculations
There are no changes to the methodology or recalculations for the 2002 inventory.
6.5.6 Source-specific planned improvements
The work of NzOnet will continue in order to better quantify N2O emission factors for New Zealand's pastoral agriculture.
6.6 Prescribed burning of Savanna (CRF 4E)
6.6.1 Description
Prescribed burning of savanna is not a key source category for New Zealand. Previous inventories have not reported emissions from savanna burning, however there is limited burning of tussock (Chionochloa) grassland in the South Island for pasture renewal and weed control. This tussock burning is included in the savanna category for the 2002 inventory. The amount of burning has been steadily decreasing since 1959 as a result of changes in lease tenure and a reduction in grazing pressure. In 2002, total emissions accounted for 1.00Gg of CO2 equivalent - a 70.2% reduction from the 3.34Gg CO2 equivalent estimated in 1990.
The IPCC Guidelines (1996) state that in agricultural burning, the CO2 released is not considered to be a net emission as the biomass burned is generally replaced by regrowth over the subsequent year. Therefore the long term net emissions of CO2 are considered to be zero. However the by-products of incomplete combustion, CH4, CO, N2O and NOx, are net transfers from the biosphere to the atmosphere.
6.6.2 Methodological issues
New Zealand has adopted a modified version of the IPCC methodology (IPCC, 1996). The same five equations are used to calculate emissions however instead of using total grassland and a fraction burnt, New Zealand uses statistics of the total amount of tussock grassland that has been granted a consent (a legal right) under the Resource Management Act (1991) for burning. Only those areas with a consent are legally allowed to be burned. Expert opinion obtained from land managers is that approximately 20% of the area allowed to be burnt is actually burnt in a given year.
Current practice in New Zealand is to burn in damp spring conditions which reduces the amount of biomass consumed in the fire. The composition and burning ratios used in calculations are from New Zealand specific research (Payton and Pearce, 2001) and the IPCC reference manual (1996). The sources are identified in the worksheets accompanying this chapter.
6.6.3 Uncertainties and time-series consistency
The same sources of data and emission factors are used for all years. This gives confidence in comparing emissions through the time-series from 1990 and 2002. The major sources of uncertainty are the percentage of consented area actually burnt in that season, that biomass data from two study sites are extrapolated for all areas of tussock, and that many of the other parameters (i.e. the carbon content of the live and dead components, the fraction of the live and dead material that oxidise and the N:C ratio for the tussocks) are the IPCC default values. Uncertainty in the New Zealand biomass data has been quantified at ±6% (Payton and Pearce, 2001), however many IPCC parameters vary by ±50% and some parameters lack uncertainty estimates.
6.6.4 Source-specific QA/QC and verification
There was no source specific QA/QC for this category.
6.6.5 Source-specific recalculations
The 2002 inventory is the first inventory to report emissions from savanna burning.
6.7 Field burning of agricultural residues (CRF 4F)
6.7.1 Description
Burning of agricultural residues produced 29.931Gg CO2 equivalent in 2002. Emissions are currently 18.4% over the 1990 baseline. Burning of agricultural residues is not identified as a key source for New Zealand.
New Zealand reports emissions from burning barley, wheat and oats residue in this category. Previous inventories have also included maize, but this is now excluded as maize residue is not burnt in New Zealand. New Zealand uses three-year averages of crop production in combination with the IPCC default emission ratios and residue statistics. Oats are included under the same emission factors as barley.
The amount of crop residues produced varies by country, crop and management system. Burning of crop residues is not considered to be a net source of CO2 because the CO2 released into the atmosphere is reabsorbed during the next growing season. However, the burning is a source of emissions of CH4, CO, N2O and NOx (IPCC, 1996).
6.7.2 Methodological issues
The emissions from burning of agricultural residues are estimated in accordance with the IPCC guidelines (IPCC, 1996). The calculation uses crop production statistics, the ratio of residue to crop product, the dry matter content of the residue, the fraction of residue actually burned, the fraction of carbon oxidised and the carbon fraction of the residue. These figures are multiplied to calculate the carbon released. The emissions of CH4, CO, N2O and NOx are calculated using the carbon released and an emissions ratio. N2O and NOx emissions calculations also use the nitrogen to carbon ratio.
6.7.3 Uncertainties and time-series consistency
No numerical estimates for uncertainty are available for these emissions. The fraction of agricultural residue burned in the field is considered to make the largest contribution to uncertainty in the estimated emissions (IPCC, 2000). Good practice suggests that an estimate of 10% of residue burnt may be appropriate for developed countries, however New Zealand estimates that 50% is burnt. This figure is developed from expert opinion of MAF officials working with the arable production sector.
6.7.4 Source-specific QA/QC and verification
There was no source specific QA/QC for this category.
6.7.5 Source-specific recalculations
There are no recalculations for this category.
Worksheets accompanying the agriculture sector
The worksheets for the agriculture sector document the underpinning data (livestock population data and timeseries) emission factors, calculations and emissions data used to collate emissions from the agriculture sector.
