The application of nitrogen (N) fertilisers to agricultural soils is a major source of nitrous oxide (N 2 O) emissions. The Intergovernmental Panel on Climate Change (IPCC) has set a default emission factor of 1% (EF 1) for N fertiliser applied to managed agricultural soils. This value does not differentiate between different N fertiliser formulations or rates of N application. The objective of this field study under spring barley was to determine N 2 O EF's for different N fertiliser formulations including urea and urea stabilised with the nitrification inhibitor dicyandiamide (DCD) and/or the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) and to evaluate their N 2 O loss abatement potential relative to calcium ammonium nitrate (CAN). The highest EF 1 measured was 0.49% for CAN which was less than half the IPCC default value of 1%. While the urease inhibitor did not reduce emissions relative to CAN; the nitrification inhibitor significantly reduced emissions compared to CAN with EF 1 as low as 0.00% for a typical spring barley site. There was no significant impact of CAN or urea application rate on EF 1 but there was a significant negative relationship 2 observed for urea in 2013. The study highlights the importance of generating higher Tier emission factors in terms of fertiliser type for use in national inventories.

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