Developing revised emission factors for nitrous oxide emissions from agricultural pasture treated with nitrification inhibitors
Objectives
The project comprised two parts. Objectives specified in the contract for the Part I are:
• Review national and international literature on the effectiveness of nitrification inhibitors in reducing direct and indirect N2O emissions from grazing animal urine and dung excreta, nitrogen fertiliser and soils. Assess the relevance of the literature and the scientific rigour applied in the work.
• Develop criteria through which non-peer-reviewed literature will be assessed. Non-peer reviewed literature will then be assessed according to the criteria and, where appropriate, findings incorporated in the report.
• Develop revised emission factors for EF1, EF3(PRP), and FracLEACH or any other emissions factors that might be modified, under a range of scenarios building on and refining the method of Clough et al. (2006), including:
• Rate and application of nitrification inhibitors (per hectare);
• The formulations, methods and circumstances (including timing) through which nitrification inhibitors are applied that may affect annual emission factors
• Number of hectares applied with nitrification inhibitors and the soil’s drainage class that can strongly affect EF3(PRP);
• The stocking and production rates that determine nitrogen excretion rate
• Historical time series from date of first use of nitrification inhibitors,
• Any other factors that might be relevant in assessing the level of emission reduction due to nitrification inhibitors
• The derivation of these factors will:
• Quantify the level of uncertainty associated with each emission factor and its associated nitrification efficacy factor (fractional reduction in emission factor attributable to the use of the inhibitor) and the reasons for this uncertainties;
• Compare uncertainties with general uncertainties from nitrous oxide emissions from the agricultural sector; and
• Be consistent with the principles of Inter-governmental Panel on Climate Change (IPCC) Good Practice Guidance in that the data are transparent, accurate, complete and consistent2.
• Compare the revised factors with:
• IPCC default emissions factors;
• New Zealand Specific emission factors
• Emissions factors developed by other countries.
• Complete the Ministry for the Environment checklist for inventory change approval.
The objectives specified in the contract for the Part II are:
• Describe how anthropogenic emissions of N2O are reduced below that which would have occurred in the absence of the use of the nitrification inhibitors.
• Compare the likely reduction in emissions with those calculated elsewhere, if available, for Clean Development Mechanisms (CDM) and Joint Implementation (JI) agreements involving nitrification inhibitors.
To our knowledge, comparable CDM or JI agreements involving nitrification inhibitors were not available for comparison. Consequently, this objective will not be considered further in the report.
• Estimate future use of nitrification inhibitors and limitations to their use, and impact on emissions until the end of Commitment Period 1 to enable an estimate of future liabilities associated with N2O emissions.
• Recommend how the revised factors should be monitored, including the long-term effectiveness of nitrification inhibitors as a nitrification inhibitor
• The production rate and number of animals (based on farm records) grazing on pastures treated and not treated with nitrification inhibitors and the soil’s drainage class (based on treated area soil inspections)
• The rate of nitrification inhibitors applied, in terms of total treated hectares (based on certified applicator GPS records) and dosage in kilograms of nitrification inhibitors per hectare (also based on certified applicator records)
• The relative effectiveness of nitrification inhibitor products available
Most nitrification inhibitors have not been assessed for their effectiveness in reducing N2O emissions from grazed pasture systems. This fact rendered much of the international literature irrelevant to the project. Further, it is essential that application of the nitrification inhibitor to New Zealand soils is sustainable including no deleterious environmental consequences. Dicyandiamide (DCD) (chemically written as C2H4N4) has been studied for more than 80 years (for example, McGuinn 1924) and it has been subject to many tests with no reported environmental side effects (Suter et al. 2006). Suter et al. (2006) determined that DCD and DMPP were the available nitrification inhibitors most suited for use in pastoral systems. The reader is also directed to a review done in New Zealand by Edmeades (2004). In New Zealand, Suter et al. reported DMPP is only available as a coated ammonium nitrate fertiliser. They concluded that this form of DMPP delivery would greatly limit its efficacy with respect to urine excreta patches in soils beneath grazed pasture and also make the inhibitor’s use cost prohibitive. Research trials using DCD have recently been conducted in New Zealand’s pastoral agricultural system. In agreement with Suter et al. (2006), we focus on DCD. Consequently, this objective will not be considered further in the report.
• any other factors that may be relevant to national N2O emissions related to nitrification inhibitors
• provide a draft report of Part II
2 Definitions of these terms by the UNFCCC are:
Accuracy: Estimates should be accurate in the sense that there is no systematically over or under bias in emissions or removals as far as can be judged, and that uncertainties are reduced as far as practicable.
Transparency: means that assumptions and methodologies used for an inventory should be clearly explained to facilitate replication and assessment of the inventory by users of the reported information.
Consistency: an inventory should be internally consistent in all its elements with inventories of other years. An inventory is consistent if the same methodologies are used for the base and all subsequent years and if consistent data sets are used to estimate emissions or removals from sources or sinks.
Completeness: an inventory covers all sources and sinks ,as well as gases, included in the IPCC Guidelines as well as other existing relevant source/sink categories which are specific to individual Annex I Parties. Completeness also means full geographic coverage of sources and sinks of an Annex 1 Party.
Contact for Enquiries
Sustainable Land Management and Climate Change
MAF
Pastoral House
25 The Terrace
PO Box 2526, Wellington
Tel: 0800 CLIMATE (254 628)
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