Fertiliser the main source of greenhouse gases from Irish agriculture – Study finds

Fertiliser is now the main source of N2O emissions from Irish agriculture, according to research carried out by Teagasc and Agri-Food and Biosciences Institue (AFBI).

Speaking of research findings at today’s fertiliser industry meeting at the Botanic Gardens, AFBI’s Rachael Carolan said that emissions from slurry and manure were lower than expected.

“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 greenhouse gas reporting.

This results in fertiliser becoming the main source of N2O emissions from Irish agriculture.

To off-set some of the impact of greenhouse gas emissions, particularly from Nitrogen-based fertilisers, Teagasc and AFBI have carried out research on the use of urea.

This research was carried out in Teagasc Johnstown Castle and it has highlighted practical ways to reduce greenhouse gas emissions and maintain production.

According to Teagasc, the form of Nitrogen (N) fertiliser used can have a big impact on the level of greenhouse gas emissions and Calcium Ammonium Nitrate (CAN) is the most widely used form on Irish farms.

Teagasc’s Dr Patrick Forrestal said that making the switch to stabilised urea from CAN can have a positive impact on greenhouse gas emissions from fertiliser spreading.

“The project found that switching from CAN to urea with the urease inhibitor (stabilised urea) reduced direct greenhouse gas 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%.

Also speaking at the event, Teagasc Dr Karl Richards said that this is exciting research, as it can save farmers money, maintain yields and nitrogen use efficiency.

Benefits of using urea with a urease inhibitor:
  • 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%.
  • NBPT treated urea is generally less expensive than CAN.
  • Averaged over all grassland sites, switching from CAN to NBPT treated urea reduced direct emissions of the Greenhouse gas N2O by 73%.