The volume of slurry and soiled water produced on dairy farms is "underestimated" compared to current regulations, according to new results from a major Teagasc project.

Slurry allowances used to "quantify the volume of slurry a dairy cow produces" have been in place since the nitrates directive came into effect in Ireland in 2006.

However these allowances do not, according to Teagasc, reflect the "dramatic increase in the productivity of the typical dairy cow in Ireland".

Currently farmers must have provision for 0.33m3 (330 litres) per cow per week for slurry storage and 0.21m3 (210 litres) per cow per week for soiled water storage - plus an allowance for rainfall runoff from any adjacent uncovered areas.

However, based on the latest Teagasc research - which included a survey of 100 farms to assess current volumes of dairy soiled water and slurry produced - data would suggest present regulations may not have kept pace with industry growth rates.

The results of the project point to "higher milk yields and more slurry output, necessitating more capacity than previously mandated by outdated benchmarks".

It also suggests that there is a "significant volume of water" getting into storage tanks on farms - equivalent of approximately 20-40 L/cow/week on average.

The slurry and dairy soiled water volume estimates project ran from October 2022 to March 2025 and continuously monitored the volumes stored.

According to Teagasc phase 1 of the research project (July 2023 – June 2024) was carried out during a "relatively wet period" with sustained adverse weather.

Phase 2 (July 2024 – March 2025) was "relatively dry" and peak rates of slurry and soiled water collection did not vary widely, despite clear differences in seasonal patterns of collection.

"Farm derogation status did not have a significant impact on slurry volumes collected," it added.

The results from this research will be reviewed by the Department of Agriculture, Food and the Marine (DAFM) and could result in "potential changes to current regulations".

Teagasc has warned that this may lead to farmers facing significant costs to provide "additional storage capacity".

"This project will provide data to DAFM to inform policy associated with the Nitrates Action Programme (NAP), any changes to current regulations will be dependent on the consideration of a range of associated issues by DAFM, in addition to this data," it added.