To assess the potential for urea plus a urease inhibitor (Agrotain), and urea plus urease and nitrification (DCD) inhibitors, to reduce nitrous oxide emissions from grassland compared to calcium ammonium nitrate (CAN), while maintaining sward production.
The form of N that is surface applied can have a major effect on N2O emissions, particularly in regions like Northern Ireland with a mild, wet climate and high organic matter soils. N2O emissions have been shown to be up to 3 times greater from a nitrate containing source (e.g. calcium ammonium nitrate CAN) compared to ammonium based fertilizers. CAN is the dominant form of synthetic fertilizer used in Ireland. However, switching from CAN to urea fertilizer will increase emissions of ammonia. Urea can be an inefficient N source due to NH3 volatilisation. Urease inhibitors reduce NH3 losses by slowing down the hydrolysis of urea making it a suitable all year round fertilizer. Urea is considerably cheaper than CAN in the UK and has a higher N content (46%N), so there could be a cost – benefit in using urea amended with a urease inhibitor instead of CAN, if DM yields were comparable. The additional benefit in using amended urea rather than a nitrate based fertilizer is the potential reduction in N2O emissions, under wet conditions. It is expected that the results of this research will demonstrate that switching from CAN to Agrotain amended Urea significantly reduces N2O emissions as well as transportation & spreading costs per ton of N, since Urea contains 46%N whereas CAN only contains 27.5%N.