Teagasc has provided estimated results of the first year of a two-year study to determine soiled water and slurry quantities produced on dairy farms.
The estimates indicate that the volume of slurry produced by a cow is underestimated currently, as is the soiled water produced on farm.
Teagasc noted that the current slurry volumes 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, despite a significant increase in the productivity of the typical dairy cow in Ireland.
The estimates also suggests that there is a significant volume of water getting into storage tanks on farms, amounting to the equivalent of approximately 20-40L/cow/week on average.
However, Teagasc said that this data is preliminary and should not be interpreted as the final outcome of the survey.
In late 2022, the Department of Agriculture, Food and the Marine requested that Teagasc outline a methodology to assess current volumes of dairy soiled water and slurry produced on dairy farms. In response to this, a survey of 100 dairy farms was proposed.
The resulting project was agreed to run from 01/10/2022 to 31/03/2025. An initial phase was completed in winter 2022/23 and, subsequently, a full-scale farm-monitoring regime was established on 100 farms spread nationwide, starting in July of 2023.
The estimates Teagasc have provided cover the first year of the survey, up to June 2024.
Current regulations require a storage allowance of 0.33m3 (330L) per cow per week for slurry storage while the accepted figure for soiled water storage is 0.21m3 (210L) per cow per week. For all storage tanks, an additional allowance is required for rainfall runoff from any adjacent uncovered areas.
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, such as rainwater or silage effluent.
In each independent storage tank, measuring equipment was installed to continuously monitor the volumes stored.
In analysing the data collected, tanks were categorised into those collecting slurry only, soiled water only, or combined slurry and soiled water tanks.
In all cases, the contribution from rainfall varied between farms, and week by week.
For slurry-only tanks, from November to February, the mean volume collected was 413.8L/cow/week, which includes rainfall runoff amounting to the equivalent of approximately 20-40L/cow/week on average.
For soiled water-only tanks, the mean volume collected in peak months, July-October 2023 and March-June 2024, was 300L/cow/week, which includes rainfall runoff amounting to the equivalent of approximately 20-40L/cow/week on average.
The peak volume collected for slurry and soiled water tanks was in October 2023 at 626.7 L/cow/week. Total volumes collected include rainfall runoff amounting to the equivalent of approximately 20-40L/cow/ week on average.
Teagasc said that the second year of monitoring is required to provide a full understanding of overall volumes collected.
The survey project will provide data to the department to inform policy associated with the Nitrates Action Programme. However, any changes to current regulations will be dependent on the consideration of a range of other issues in addition to this data.