Teagasc conducted a survey of 100 farms to assess current volumes of dairy soiled water and slurry produced on dairy farms.
The Slurry and dairy soiled water volume estimates project ran from October 2022 to March 2025, beginning with a winter 2022/23 phase to refine measurement methods and collect baseline data, followed by full-scale nationwide monitoring.
On each selected farm, a number of surveys were completed to catalogue both the storage facilities and the typical management with regard to stock, parlour details, washing routine, uncovered areas and potential additional sources (rainwater, silage effluent etc.). In each independent storage tank, measuring equipment was installed to continuously monitor the volumes stored.
The survey found that on dairy farms the volume of slurry and soiled water produced is underestimated presently compared to the current regulations which require 0.33 m3/cow/week for slurry storage and 0.21 m3/cow/week for soiled water storage, plus an allowance for rainfall runoff from any adjacent uncovered area.
This outcome reflects higher milk yields and more slurry output, necessitating more capacity than previously mandated by outdated benchmarks.
The current slurry allowances used to quantify the volume of slurry a dairy cow produces have been in place since the nitrates directive was implemented in Ireland in 2006. This is despite a dramatic increase in the productivity of the typical dairy cow in Ireland.
The results of this study suggest that the volume of slurry produced by a cow is underestimated currently, as is the soiled water produced on farm. This study also suggests that there is a significant volume of water getting into storage tanks on farms, amounting to the equivalent of approximately 20-40 L/cow/week on average.
While Phase 1 of this study (July 2023 – June 2024) was carried out during a relatively wet period with sustained adverse weather and Phase 2 (July 2024 – March 2025) was relatively dry, 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.
The report will provide guidance to the Department of Agriculture, Food and the Marine to inform policy associated with any potential changes to current regulations. Farmers will face significant costs to provide additional storage capacity should these higher rates be adopted and must plan ahead for investments, possibly using the Nutrient Storage Investment Scheme (TAMS 3).
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