The Environmental Protection Agency (EPA) recently published a report based on analyses of catchments where nitrogen concentrations in water were too high.

The report, Assessment of the catchments that need reductions in nitrogen concentrations to achieve water quality objectives was published just in advance of the EPA Water Conference 2021, which carried the theme of ‘Water: integrating policy and practice’.

The report reveals some really interesting nuggets about nitrogen, and how high concentrations of it in water is one of the main factors leading to poor water quality in Ireland.

Water and nitrogen

Below are some of the key messages contained within the EPA’s report.

The primary water-quality issue of concern in Ireland is elevated concentrations of nutrients called nitrogen and phosphorus. Such concentrations contribute to an increase in the growth of algae and aquatics plants, which impacts aquatic ecosystem health.

Nitrogen concentrations in waters have been increasing since 2013. Excess nitrogen in waters can also impact drinking-water quality, and Ireland’s estuaries and coastal waters, and groundwater drinking supplies, are particularly at risk.

Case in point – only 38% of our estuaries and coastal waters are meeting their water-quality targets, the report stated.

There are a number of key catchments of concern: Maigue/Deel; Bandon; Lee; Blackwater; Suir; Nore; Barrow; Slaney; Tolka/Liffey; and the Boyne river catchments.

Between 2013-2019, all but one of the catchments of concern showed increasing trends in the amount, or load, of nitrogen discharging to the sea via rivers;

Nitrogen in our waterways comes mainly from agriculture – chemical fertiliser and organic fertiliser (manures and urine) from livestock.

In the predominantly rural catchments, more than 85% of the sources of nitrogen in the catchment are from agriculture.

Excess nitrogen leaches down through freely draining soils, into groundwater, and then into our rivers and streams. The more freely draining the soil is, the more favourable it is for nitrogen leaching.

The primary water-quality issue of concern in Ireland is elevated concentrations of nutrients called nitrogen and phosphorus.

Many variables determine how much of the nitrogen used in farming ends up in our waterways, including farm practice, soils, climate and losses to air.

About 25% of the nitrogen used on land is captured in the food that is produced and the remainder is either available for losses to the environment or is stored in the soil organic matter.

The Ag Climatise roadmap has set a target of an absolute reduction in the overall level of nitrogen fertiliser being used on Irish farms from a high of 408,000t in 2018 to 325,000t in 2030.