Ammonia emissions from pasture-based production systems: a collation of Irish research

Keywords: ammonia volatilisation, grassland, slurry, pasture-based, fertiliser, nitrogen.

Ammonia (NH3) emissions are a major concern for livestock production systems due to the economic loss of nitrogen (N) from the system and more imminently due to challenging National Emissions Ceiling targets established to reduce the environmental impacts associated with NH3 emissions. Intensive pasture-based systems in particular, with their relative high requirement for N inputs, face a major challenge to continuing to produce food sustainably while reducing or limiting NH3 emissions. Ammonia emissions research on pasture-based systems in Ireland has been on-going for over thirty years and has encompassed the major sources of emissions along the manure management chain and fertiliser N emissions.

The objective of this paper is to outline the most recent NH3 research conducted in Ireland, to summarise the previous research completed on slurry land spreading and fertiliser N in Ireland, and to discuss some of the practical considerations associated with the adoption of NH3 mitigation options for pasture based systems. The majority of Irish research has focused on mitigation options at land-spreading and fertiliser N application. Of these, some of the early research on slurry acidification at land-spreading has proven it to be highly effective with NH3 emissions being reduced consistently by >80%. However, options such as application timing and application techniques, while having lower and more variable reported percentage reductions in NH3 emissions, can be more practical to implement. Until recently there has been a lack of research in Ireland on NH3 emissions from excreta deposition during grazing, concrete yards, housing and slurry storage, which together account for up to 67% of Irish agricultural NH3 emissions.

Recent research in Ireland has begun to focus on these areas. Ammonia emissions associated with concrete yards (22 to 29% total N lost as NH3) and cattle building (7.8% total N lost as NH3 on average) were higher than those found for excreta deposited at pasture (6.06% total N lost as NH3 on average), thus illustrating that increasing the grazing season length has the potential to reduce NH3 emissions. Switching fertiliser N formulation from urea to calcium ammonium nitrate (CAN) or stabilised urea is very effective, giving 84% and 78% reductions on average in Irish trials, respectively. Such a change is practical at farm level but may increase fertiliser N costs. In conclusion, there are many options available to reduce NH3 emissions on pasture-based systems. Their practicality and additional costs must be considered if they are to be adopted at farm level.

William Burchill Crops, Environment & Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Co. Wexford, Ireland and Teagasc Kanturk, Percival Street, Kanturk, Co. Cork, Ireland.

Patrick J Forrestal, Crops, Environment & Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Co. Wexford, Ireland.

Ian Kavanagh, Crops, Environment & Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Co. Wexford, Ireland.

Gary J Lanigan, Crops, Environment & Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Co. Wexford, Ireland.

36 pages, 13 figures, 5 tables, 72 references