The latest environmental statistics for Northern Ireland (NI) confirm that ammonia emissions from agriculture are still on the rise.
The figures were published by the Department of Agriculture, Environment and Rural Affairs (DAERA).
They indicate that the agriculture sector accounted for the majority of ammonia emissions in Northern Ireland in 2021.
Sources of ammonia emissions
Other sources of ammonia emissions include transport, commercial and domestic combustion and industrial processes.
In 2021, of the ammonia emissions from agriculture, 86% came from livestock, 8% from the application of fertilisers containing nitrogen and 6% from the application of other organic materials to land (sewage sludge and digestate).
Estimates of total ammonia emissions from agriculture are based on numbers of cattle, sheep, pigs, poultry, horses, goats and deer together with associated information on livestock and manure management practices and the use of nitrogen-containing fertilisers.
Emissions from livestock have increased by 9.1% since 2001 (from 25.3kt to 27.6kt in 2021).
This compares with a 14.8% decrease for the UK as a whole over the same period. Cattle numbers have declined to a lesser extent in NI compared with the UK as a whole.
Dairy cow, pig and poultry numbers have increased over this period in NI in contrast to decreasing or stable populations for the UK as a whole.
Nitrogen fertiliser
The ammonia emissions from nitrogen fertilisers have declined by 0.7kt (from 3.3kt in 2001 to 2.6kt in 2021), a 21% decrease.
According to DAERA, this is directly associated with a significant reduction in fertiliser use, particularly on grassland. Overall, ammonia emissions have increased, by 12.1%, from 28.5kt in 2001 to 32kt in 2021.
In contrast, an improving picture has evolved where nitrate (NO3) pollution of surface waters in NI is concerned.
Under the European Union Nitrates Directive, NI must monitor surface waters for NO3 pollution, against a mandatory standard of 50mg NO3/L.
In addition, a guide standard for surface waters is operational where 90% of samples should be less than 25mg NO3/L.
In the period 2000 to 2011, over 99% of sites had an annual mean concentration of less than 25mg NO3/L. In the period 2012 to 2016, all rivers that were monitored for nitrate had an annual mean concentration of less than 25mg NO3/L.
In 2021, 100% of sites had an annual mean concentration of less than 25mg NO3/L.
Long-term seasonal trend analysis shows that the monthly trends in average nitrate concentrations in rivers in NI are predominantly decreasing or stable over the 28-year period, 1992-2019.