Nitrous Oxide Emissions in Spring Barley Production As Influenced By Fertiliser Nitrogen Source and Inhibitor Selection.

Agriculture is responsible for 29% of total greenhouse gas (GHG) emissions in Ireland and for 84% of global anthropogenic nitrous oxide (N₂O) emissions. Ireland has set targets under the Kyoto protocol to reduce GHG emissions to 13% above 1990 levels by 2020. The addition of nitrogen (N) fertilisers to soils is one of the main contributors to N₂O emissions in agriculture. In Ireland calcium ammonium nitrate (CAN) is the dominant source of (N) fertiliser used in spring barley production. Fifty percent of N in CAN is in the nitrate form which primes the soil system for N₂O loss under environmental conditions which favour denitrification. Switching from ammonium nitrate to urea based fertiliser holds potential for reducing N₂O losses, but could increase N loss through ammonia volatilisation. The inclusion of a urease inhibitor with urea is a volatilization loss mitigation strategy. Addition of a nitrification inhibitor delays the conversion of ammonium to nitrate thus reducing the pool of soil nitrate available for denitrification. The objectives of this study are to assess a) the effect of switching from ammonium nitrate to urea based fertiliser, b) the effect of the nitrification inhibitor dicyandiamide, and c) the effect of the urease inhibitor (N-(n-butyl) thiophosphoric triamide) on N₂O emissions from spring barley production in a temperate maritime climate. Initial results indicate that fertiliser nitrogen source and inhibitor selection affect N₂O emissions in spring barley production.