Completeness Time series QAQC


Complete coverage of the direct and indirect N2O emissions from managed land requires estimation of emissions for all of the anthropogenic inputs and activities (FSN, FON, FCR, FPRP, FSOM and FOS), if they occur. Experience has shown that none of these sub-categories are likely to be missed in inventories, although countries may have difficulty obtaining accurate statistics for all sub-categories, particularly the amounts of crop residues (by crop type) that are typically returned to soils, and the area of drained/managed organic soils.

Currently, the IPCC method does not explicitly address activities such as plastic sheeting or greenhouse hydroponic systems that may influence N2O emissions. These additional activities can be considered if appropriate, and if national activity data for these activities are collected. Some of these activities can be readily included in national inventories based on available information. For the additional commercial and noncommercial organic fertilisers, the default emission factor used for applied N may be used. Further research will be required to develop the flux data that are needed to develop emission factors for use of plastic sheeting and hydroponic systems in horticultural areas.


Ideally, the same method is used throughout the entire time series. However, it is likely that the detail and disaggregation of emissions estimates from this source category will improve over time. In cases where some historical data are missing, it may be necessary to derive the data using other references or data sets. For example, annual data of areas for drained/managed organic soils may need to be derived by interpolation from a longer time series based upon long-term trends (e.g., from decadal statistics over a 20- or 30-year period). Estimates of the amounts of crop residue incorporated annually may also need to be derived based on expert judgment.

Interannual changes in FracGASF, FracGASM, FracLEACH, EF4, and EF5 are not expected unless mitigation measures are undertaken. These factors should be changed only with the proper justification and documentation. If updated defaults for any of these variables become available through future research, inventory agencies may recalculate their historical emissions.

It is important that the methods used reflect the results of action taken to reduce emissions and the methods and results are thoroughly documented. If policy measures are implemented such that activity data are affected directly (e.g., increased efficiency of fertiliser use resulting in a decrease in fertiliser consumption), the effect of the policy measures on emissions will be transparent, assuming the activity data are carefully documented. In cases where policy measures have an indirect effect on activity data or emission factors (e.g., a change in animal population feed practices to improve animal productivity that results in a change in N excretion per head), inventory input data should reflect these effects. The inventory text should thoroughly explain the effect of the policies on the input data.


Tier 1 checks of the emission estimates should be undertaken by the persons preparing the inventory along with expert review by people outside the inventory preparation process. Additional Tier 2 quality control checks and quality assurance procedures may also be applicable, particularly if higher tier methods are used to determine direct and indirect N2O emissions from this source category. Supplement the general QA/QC related to data processing, handling, and reporting, with source-specific category procedures discussed below. The persons who collect data are responsible for reviewing the data collection methods, checking the data to ensure that they are collected and aggregated or disaggregated correctly, and cross-checking the data with previous years to ensure that the data are reasonable. The basis for the estimates, whether statistical surveys or 'desk estimates', must be reviewed and described as part of the QC effort. Documentation is a crucial component of the review process because it enables reviewers to identify mistakes and suggest improvements.

Review of emission factors

The inventory compiler should review the default emission factors and document the rationale for selecting specific values.

If using country-specific factors, the inventory compiler should compare them to the IPCC default emission factors. Also, if accessible, relate to country-specific emission factors used by other countries with comparable circumstances. Differences between country-specific factors and default or other country factors should be explained and documented.

Review of any direct measurements

If using factors based on direct measurements, the inventory compiler should review the measurements to ensure that they are representative of the actual range of environmental and soil management conditions, and inter-annual climatic variability, and were developed according to recognised standards (IAEA, 1992).

The QA/QC protocol in effect at the sites should also be reviewed and the resulting estimates compared between sites and with default-based estimates.

Activity data check

The inventory compiler should compare country-specific data on synthetic fertiliser consumption with fertiliser usage data from the IFA and synthetic fertiliser consumption estimates from the FAO.

The inventory compiler should ensure that N excretion data are consistent with those used for the manure management systems source category.

National crop production statistics should be compared to FAO crop production statistics.

The inventory compiler should ensure that the QA/QC has been completed for livestock characterisation, because data are shared with the livestock section.

Country-specific values for various parameters should be compared to IPCC defaults and any significant differences explained.

External review

The inventory compiler should conduct expert (peer) review when first adopting or revising the method. Given the complexity and uniqueness of the parameters used in calculating country-specific factors for these categories, specialists in the field should be involved in such reviews.


Direct and Indirect N2O Emissions

Document and archive all information required to produce the national emissions inventory estimates. Direct and indirect N2O emissions from managed soils are reported in aggregate or disaggregated by land-use category or other subcategory (e.g., ricelands) under the IPCC category 'AFOLU'. Reporting should be done at the same level of disaggregation as was done when calculating the emissions. In addition to completing the reporting formats, the following additional information is necessary to document the estimate:

Activity data: Sources of all activity data used in the calculations (i.e., complete citations for the statistical databases from which data were collected), and in cases when activity data were not available directly from databases, the information and assumptions that were used to derive the activity data. This documentation should include the frequency of data collection and estimation, and estimates of accuracy and precision.

Emission factors: The sources of the emission factors that were used (specific IPCC default values or otherwise). In inventories in which country- or region-specific emission factors were used, or in which new methods (other than the default IPCC methods) were used, the scientific basis of these emission factors and methods should be completely described and documented. This includes defining the input parameters and describing the process by which these emission factors and methods are derived, as well as describing sources and magnitudes of uncertainties.

Emission results: Significant fluctuations in emissions between years should be explained. A distinction should be made between changes in activity levels and changes in emission, volatilisation and leaching factors from year to year, and the reasons for these changes documented. If different factors are used for different years, the reasons for this should be explained and documented.

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