Balancing Greenhouse Gas and Agricultural Production Targets on Irish Farms

Research undertaken by both Teagasc and the Agri-Food and Biosciences Institute (AFBI) has highlighted practical ways for agriculture to reduce greenhouse gas emissions, maintain production and save farmers money. Scientists from Teagasc and AFBI presented key results from a multi-site and multi-year experimental field trial that focussed on both grassland and spring barley. These trials evaluated the effects of fertiliser formulation and organic excreta on the potent greenhouse gas nitrous oxide (N2O) and on the air pollutant ammonia (NH3). Recently published results were presented today, Friday, 10 June to stakeholders from the farming industry, fertiliser industry and government policymakers at a meeting in Teagasc National Botanic Gardens.

The SUDEN/AGRI-I projects are funded by the Department of Agriculture, Food and the Marine (RSF 10/RD/SC/716 and 11/S/138) and the Department of Agriculture, Environment and Rural Affairs in Northern Ireland (AFBI, E&I 13/4/06). The experimental trial sites included Johnstown Castle, Co. Wexford (Teagasc), Moorepark, Co. Cork (Teagasc) and Hillsborough, Co. Down (AFBI).

Striking a Balance

EU member states have committed to reduce their overall greenhouse gas (GHG) emissions by 20% by 2020 and to reduce emissions of the air pollutant ammonia. Simultaneously, ambitious agricultural production targets have been set both North and South in response to the increased demands for food and abolition of EU milk quotas (Going for Growth 2020; Food Wise 2025). In order to achieve these targets, the farming industry is facing increasing pressure to simultaneously increase yields, to improve nitrogen (N) use efficiency whilst reducing emissions of the potent GHG N2O and ammonia. These emissions are associated with the application of mineral and organic N fertilisers.

Teagasc and AFBI have collaborated for the last 3 years to investigate agricultural N2O emissions and ways to reconcile both production and environmental targets. Dr. Rachael Carolan, Agri-Food & Biosciences Institute, Northern Ireland said: “The project highlighted that greenhouse gas emissions associated with dung and urine excreta deposited by grazing animals were 85 and 41% lower respectively compared to the international factor used for national GHG reporting. This results in fertiliser becoming the main source of N2O emissions from Irish agriculture.”

The project further investigated ways to reduce GHG emissions from fertiliser. The form of N fertiliser used can have an impact on the magnitude of GHG emissions. CAN is currently the most widely used straight fertiliser N source in Ireland. Dr Patrick Forrestal Teagasc Johnstown Castle said: “The project found that switching from CAN to urea with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) reduced direct GHG emissions associated with fertiliser application by 73% on average in grassland. Treating urea fertiliser with NBPT also reduced ammonia losses by up to 78.5%.”

Dr Karl Richards summarised the event by saying “This exciting research has highlighted that switching from CAN to urea treated with NBPT saves the farmer money, while simultaneously maintaining yields and nitrogen use efficiency and reducing greenhouse gas emissions.”

Results from these multi-site and multi-year Irish field trials show that:

• Fertiliser nitrogen is the main source of the potent Greenhouse gas N2O on Irish farms.
• Averaged over all grassland sites, switching from CAN to NBPT treated urea reduced direct emissions of the Greenhouse gas N2O by 73%
• CAN and NBPT treated urea consistently produced similar yields and N off-take in grassland and spring barley
• Untreated urea had lower fertiliser N recovery and therefore lower efficiency than both NBPT treated urea and CAN
• NBPT reduced NH3 volatilisation from urea fertiliser by 78.5%. As a result NBPT treated urea is approximately equivalent to CAN in terms of NH3 loss
• NBPT treated urea is generally less expensive than CAN

More detail on the projects can be found on the website http://agri-i.ie/

Under Irish soil and climate conditions, replacing CAN with stabilised urea is an effective mitigation strategy to reduce N2O emissions, whilst maintaining current production levels.