Introducing management strategies to help reduce ammonia (NH₃) emissions and lessen the impact of the chemical on the surrounding environment is crucial.

However, it is important to first of all understand the emission sources and magnitude of nitrogen (N) release to navigate the ‘pinch points’ on farm where you can employ innovative technologies to achieve maximum impact.

Senior air quality technologist, Judith McCord states that modelling of the College of Agriculture, Food and Rural Enterprise (CAFRE) Dairy Centre inputs through the National Ammonia Reduction Strategy Evaluation System (NARSES) allowed the flow of total N and total amount of ammoniacal N (TAN) to be quantified.

The use of this farm ammonia modelling tool identified where ammonia is produced and how N is managed through the farm enterprise cycle.

The ammonia assessment was compiled using farm data relating to herd and manure management from the following three age stages of livestock:

Dairy cows;
Dairy calves (0-1-years-of-age);
Dairy replacement heifer (1-2-years-of-age).

CAFRE commissioned the Agri-Food and Biosciences Institute (AFBI) to work on the modelling of farm ammonia emissions with and without ammonia mitigation technologies applied.

The modelling assessed a range of legislative and voluntary measures implemented at the CAFRE Dairy Centre.

Reducing ammonia

Ammonia emissions for the CAFRE Dairy Enterprise for the year modelled amounted to 3.54t. This scenario comprised as follows:

187 Holstein Friesian dairy cows;
30% replacement rate;
100% stabilised urea used on grazing and forage ground (no calcium ammonia nitrate);
100% use of low emission slurry spreading equipment (LESSE);
Targeted and reduced crude protein (CP) diet of 17% for the milking herd;
Low emission flooring in the milking cow cubicle house and high frequency scraping;
All above ground slurry stores covered with an impermeable cover.

Application of slurry using LESSE reduces ammonia emissions on the CAFRE Farm Estates.

The non-mitigated comparison modelled comprised as follows:

100% calcium ammonium nitrate (CAN) (no stabilised urea)
Splash plate slurry application;
No targeted or reduced dietary protein;
Standard concrete flooring with limited scraping;
Open above ground slurry stores.

This scenario resulted in modelled emissions of 6.61t NH₃ /year.

At the CAFRE Dairy Centre, lactating dairy cows had 48% lower ammonia emissions when there were mitigation strategies implemented in comparison to having none in place.

The dairy replacement enterprise and dairy calves had 55% and 68% lower ammonia emissions respectively when the relevant mitigation technologies were applied.

McCord commented that the result was very encouraging, and said: “The use of ammonia-reducing technologies on Northern Ireland farms will help the sector reduce ammonia emissions.”

Judith McCord, senior technologist, CAFRE reports on the use of reduced and targeted crude protein diets for the dairy cattle at CAFRE.

Emission sources

The biggest hotspots for emissions within the CAFRE Dairy Centre were in the milking cow category and manure handling during housing and spreading.

Housing emissions account for 42% of the total in both the mitigated and non-mitigated scenarios. However, mitigation technologies modelled in housing such as low emission flooring and reduced protein diets accounted for reductions of 0.78t and 0.34t/year, respectively.

Emission sources on farm showed positive reductions in manure spreading and manure storage, where the use of LESSE and impermeable covered slurry stores accounted for approximately 2t/year of combined reductions.

Above ground slurry stores are covered to reduce ammonia emissions at the CAFRE Dairy Centre.

The use of protected urea in the mitigated scenario reduced the amount of total greenhouse gas emissions (GHG) emissions produced in comparison to unprotected urea.

McCord said: “Mitigation strategies that can be implemented at various stages of the system will help to reduce ammonia emissions.”

“Demonstrated clearly at CAFRE – the efficient management of nitrogen can contribute to a reduction of ammonia emissions by up to 54%.”

The top three ammonia-reduction technologies to apply on farm, based on the CAFRE ammonia emissions scenarios, are as follows:

100% use of LESSE;
Installing low emission flooring which has an ammonia efficiency factor of 11kg NH₃, alongside high frequency scraping (every 2 hours);
Reducing CP in milking cow diets by up to 2%.

Reducing ammonia

Emission sources

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