soil potential N2O emissions from Irish managed grasslands

National scale information regarding nitrous oxide (N2O) emission is important as an evidence base that underpins landuse policy and mitigation approaches. However, the highly variable rates of nitrification and denitrification make the prediction of N2O emission demanding. Here, we evaluated the role of abiotic and biotic factors on the potential denitrification and nitrification of Irish soils, in order to identify the key factors regulating potential N2O emissions at a large scale. To do so, we collected 136 soil samples from 32 sites in Ireland, and characterised the soil physico-chemical properties, the prokaryotic and fungal community composition, the abundance of N cycling communities and evaluated the soil potential nitrification, denitrification and end product N2O / (N2O + N2). We found large differences in soil potential denitrification between sites (up to 41.5 mg N kg-1 soil day-1) with most of the emissions released in the form of N2O rather than N2. Soils with highest potential nitrification rates also exhibited the highest potential denitrification rates, and similar parameters were linked to both processes. The factors most predictive of soil potential denitrification were both the soil physico-chemical properties and the prokaryotic community composition. Soil phosphorus content was as important for predicting potential denitrification as pH and total nitrogen. Soil community structure, rather than functional denitrifiers abundance, was an important predictor of the potential denitrification and the end product N2O / (N2O + N2). The prokaryotic community composition was more strongly associated with denitrification rates and the resulting end products than fungal communities. Increased relative abundance of the prokaryotic phyla Actinobacteriota and Crenarchaeota, were linked to the complete denitrification pathway. Altogether, these results lay the foundation for a better understanding of the key factors regulating the potential denitrification in Irish soils and important soil properties to consider to increase prediction of the potential denitrification at larger scales.