23 January 2025

Slurry is a valuable nutrient – use it correctly

Farmers can protect water quality, maximise nutrient efficiency and save money on chemical fertilisers when slurry is applied following best practice.

That’s according to Cathal Somers, a Water Quality Specialist at Teagasc, who joined Stuart Childs on a recent episode of the Dairy Edge podcast.

Although slurry applications are now permitted in Zones A and B, Cathal Somers commented that the optimum time for slurry applications occurs typically from mid-February onwards, when grass growth rates and soil temperatures tend to be higher, day length increases and soils tend to be drier.

Valued at €25-26/1,000 gallons due to the nutrients contained within, Cathal Somers advised farmers to treat slurry like any other fertiliser, spreading it in the right place, at the right time and at the right rate.

Calendar farming and more specifically the dates in which slurry spreading is permitted, he explained, should be used only as a guide as to when farmers are allowed to spread slurry. More important considerations for the protection of water and to ensure the nutrients contained within are used efficiently are the growth rate of the crop to which it is applied, soil temperatures, ground conditions and the forecast for the days following application.

Key points:

• Check the weather forecast before spreading slurry. Ensure there’s no heavy rain forecast.
• Apply slurry on the drier fields on the farm.
• Only spread slurry when the soil temperature is 6°C and rising.
• Slurry should be targeted at fields with a requirement for phosphorus (P) and potassium (K), typically silage fields, were soil pH is optimum to ensure the efficient use of nutrients.
• To prevent nutrient losses to water, farmers must adhere to the 10m buffer zones for two weeks following the opening of the closed period.
• The use of Pollution Impact Potential (PIP) maps is also recommended to avoid spreading slurry in fields at a heightened risk of nutrient losses.

Although holding slurry applications until mid-February is seen as best practice for the protection of water and maximising nutrient use efficiency, Cathal is aware that some farmers may have no option but to spread before then.

If finding yourself in such a position, he recommended just lowering tanks rather than emptying completely and holding the reserve of slurry for when a ‘better bang for buck’ can be achieved. On the volumes of slurry spread in the early part of the season, he advised farmers to limit applications to 1,500-2,000 gallons per acre, as excess applications over and above this can increase the risks of losses to water quality.

Where farmers are finding that they need to spread slurry in the opening days of the season, he advised them to check their slurry storage capacity and to ensure that no clean water – either flowing directly in from the yard or through malfunctioning shoots or downpipes – is entering the tanks.

For more information, listen to the full episode of the Dairy Edge podcast below:

Protecting water quality when spreading slurry

In the below video, David Melody, a dairy farmer from Co. Kilkenny, and Deirdre Glynn, a Teagasc ASSAP Advisor, remind farmers of the key considerations to bear in mind before committing to spreading slurry.