Managing fertiliser nitrogen to reduce nitrous oxide emissions and emission intensities from a cultivated Cambisol in Scotland

Abstract

Emissions of nitrous oxide (N2O) were measured from an arable site in south east Scotland for twelve months during 2011–2012 using an intensive sampling strategy. This fully replicated and blocked field experiment aimed to provide accurate measurements of N2O emissions from one of the UK's principle geoclimatic zones supporting agricultural production and to produce robust N2O emission factors (EFs). Calculated EFs were compared to the IPCC's default Tier 1 EF of 1.25%, and the new value of 1%, to assess their suitability for use in locations throughout the UK. Emissions from ten treatments fertilised with either ammonium nitrate or urea at rates of 0kgNha−1 to 200kgNha−1, and sown with spring barley, were measured using the static closed chamber technique. Potential N2O mitigation options were investigated; these included the use of a nitrification inhibitor (NI), split fertiliser applications and variations in the form and quantity of fertiliser applied. Crop yields were measured to enable calculation of N2O emission intensities for each treatment; this is an important factor to consider when assessing N2O mitigation options due to the need to maintain crop yields. Cumulative N2O emissions varied between 1.32kg N2O-Nha−1 and 3.82kg N2O-Nha−1 with a mean 42% decrease in emissions associated with the use of the NI. Increases in crop yield were associated with increases in N fertiliser application, and the amendment of treatments with a NI and the use of a split fertiliser application significantly decreased crop yields by approximately 10% and 5% respectively. Annual EFs ranged between −0.28% to 1.35%. Emission intensities decreased with increasing fertiliser application at low N application rates, and the optimum fertiliser application rate to obtain minimum emissions but maximum crop yield was 160kgNha−1.