• Three field sites:• Clay loam at

3. Methods• Three grassland field sites in Ireland:

Drainage impeded at Hillsborough, Co. Down Moderately drained at Johnstown Castle, Co.WexfordWell drained at Moorepark, Co Cork.

• Fertiliser N formulations evaluated in year 1 (2013/14) and year 2 (2014/15): CAN, Urea, Urea + n-BTPT, Urea + DCD and Urea + n-BTPT + DCD.

• Fertiliser N rates (0 – 500 kg N ha-1 yr-1) applied in five equal splits, the 200 kg N ha-1 yr-1 rate is presented.

• N2O-N emissions measured using static chambers (Fig . 1) and NH3 emissions measured using wind tunnels

(Fig 2.) to give indirect N2O emissions.

• interaction (P<0.001)

The impact of fertiliser formulation on N2O emissionsMary Harty1,3, Patrick J. Forrestal1, Rachael Carolan2, Karen L. McGeough2, Catherine J. Watson2,3, Ronnie J. Laughlin2, Dominika Krol1,

Gary Lanigan1 and Karl G. Richards1 1 Teagasc, Johnstown Castle, Environmental Research Centre, Co. Wexford, Ireland. 2 Agri-Food and Biosciences Institute, Belfast, Northern Ireland. 3 Queen’s University Belfast, Northern Ireland. mary.harty@teagasc.ie

1. Objective: To evaluate the effect of switching from calcium ammonium nitrate (CAN) to urea or urea with the urease inhibitor N-(n-butyl) thiophosphoric triamide (n-BTPT) and/or a nitrification inhibitor dicyandiamide (DCD) on nitrous oxide (N2O) emissions.

2. Introduction: Approximately 11.8% of Ireland’s national GHG emissions are due to fertiliser N application to agricultural soils (EPA, 2014). Use of nitrate-N (NO3–N) based fertilisers in a temperate maritime climate may result in fertiliser N2O-N emission factors (EFs) higher than the IPCC default of 1%. Switching from CAN to urea based fertilisers could potentially reduce N2O loss by managing the soil NO3–N pool, a key risk factor for denitrification.

4. Results: Table 1 – Direct N2O EFs (EFs in red indicate ≥ IPCC default of 1%)

This work is funded by the Walsh Fellowship programme and Department of Agriculture Food and Marine, Research Stimulus FundThe authors would like to acknowledge the help of the technical and lab staff at Teagasc and AFBI.

Reference:Environmental Protection Agency. 2014. Ireland National Inventory Report – 2014, page 116.Forrestal et al., 2015. Ammonia emissions from stabilised urea fertiliser formulations in temperate grassland. Soil Use and Management (in review)

6. Summary:• Urea formulations generated sig. lower direct N2O emissions than CAN in five of six site years (Table 1)• Nitrification inhibitor (DCD) was highly effective in lowering N2O emissions (Table 1)• Incorporation of indirect N2O EFs in overall N2O EFs brings urea EF closer to IPCC default value of 1%

although overall urea emissions are still significantly lower than overall CAN emissions (Figure 3)• The addition of urease inhibitor (n-BTPT) reduced urea indirect N2O EFs to levels comparable to CAN

(Figure 3)• Use of urea with urease and or nitrification inhibitor shows potential as a mitigation strategy for N 2O

emissions (direct and indirect) relative to CAN. • The magnitude of N2O emissions from CAN are site and rainfall dependent.• Multi-site and year datasets are critical for developing meaningful national N2O EFs.

*Treatment differences determined using F protected LSD test (P<0.05) . Direct N2O emissions for CAN significantly different to all other urea treatment s except Urea+n-BTPT in Johnstown in Year 1.** Hillsborough LTAR based on average rainfall data from 1995-2011, Johnstown and Moorepark LTAR based on average rainfall data from 1981-2010.

Fig 1 – Static Chambers

Fig 2 – Wind Tunnels

• interaction (P<0.001)

5. Results: Figure 3 – Year 2 N2O EFs Direct and Indirect

Johnstown Hillsborough