Differing effects of fertiliser use on nitrous oxide emissions from grassland sites in Ireland

Field experiments at six Irish grassland sites (2013–2014) examined the influence of nitrogen (N) fertiliser type and application rate on nitrous oxide (N₂O) emissions. Calcium ammonium nitrate (CAN) replaced with urea-based fertilisers, particularly when stabilised with inhibitors such as NBPT or DCD, reduced direct N₂O emissions by up to 80% while lowering costs. Emission factors (EFs) were strongly influenced by fertiliser formulation and rate, with CAN consistently producing higher and more variable emissions than urea. Stabilised urea (urea + NBPT) was least sensitive to increasing rates. Collectively, these studies highlight that fertiliser choice and rate are key management levers for mitigating agricultural greenhouse gases and underscore the need for country-specific emission factors to improve national greenhouse gas inventories.