End of the slurry spreading closed period guidance

Date published: 30 January 2025

However, applications of slurry and manure can only resume from this date if ground and weather conditions are suitable to allow the uptake of nutrients from the slurry, for example avoid spreading on wet or frozen ground. Care should be taken to observe the increased buffer zones and reduced application rates required by NAP during the month of February.

It must also be noted that nutrient applications whether via organic manure or chemical fertiliser must only be made where there is crop need.

Climate change is affecting our weather patterns, with heavier rainfall incidents, which can increase land run-off adding further nutrients to water bodies, and warmer temperatures affecting water conditions. This is further increasing the risk of blue-green algae forming blooms during summer and autumn months.

Increased buffer zones

During the month of February NAP states that buffer zones should increase from:

• 20m to 30m for lakes
• 10m to 15m for any other waterway
• 3m to 5m for any other waterway if using Low Emission Slurry Spreading Equipment (LESSE) in fields with an incline of less than 10% or the adjoining field is less than 1ha in size or not more than 50m wide.

Reduced application rates

During February and the first two weeks of October the maximum single application of slurry must not exceed 30m³ per ha (2,700 gallons per acre), reduced from 50 m³ per ha (4,500 gallons per acre).

During February grass growth will be limited due to lower soil temperatures and shorter day length, so the nutrient requirement is lower. By reducing the maximum single application of slurry to 30m³, it will more closely align to the nutrient requirement of the grass plant at this time, reducing the risk of surplus nutrients being lost into waterways.

Spreading conditions

Outside of the closed period, you should only apply slurry when ground and weather conditions are suitable, avoiding areas that pose a high risk of nutrient loss to waterways. Never apply nutrients to waterlogged soils, to land that is flooded or liable to flood, on frozen ground or if heavy rain is falling or forecast within the next 48 hours. Applications also cannot be made on steep slopes where a risk of water pollution exists.

Soil temperature

Spreading when soil temperatures are consistently above 6℃ is advised as it means that grass is growing and has the potential to take up nutrients. Nutrient uptake will be greater when soil temperature rises to 8-10℃ and soil biology really starts to convert nutrients into plant available forms.

The timing of slurry application has a large influence on the uptake of nutrients by plants and the potential for losses to water. Focusing slurry applications later in the spring when grass growth is higher will increase nutrient use efficiency.

Where to spread

Avoid spreading in paddocks with high connectivity to the drainage network until later in the spring when there is a lower risk of nutrient loss to water.

Spreading on sloping land

Care should be taken on all sloping land near a waterway and a risk assessment carried out to determine if you can spread fertiliser (including organic manures) on it.

The following factors must be considered in making these risk assessments:

• type and amount of fertiliser being applied,

• time to incorporation of organic manures (land other than grassland only),

• proximity of waterways,

• soil conditions and

• forecast weather condition.

The measures contained within NAP, including closed periods, buffer zones and reduced application rates are designed to improve nutrient efficiency within the farm and improve water quality. These important management practices and legal requirements apply to all farms within Northern Ireland, with the aim of improving nutrient utilisation of organic manures and chemical fertilisers while also reducing the likelihood of nutrient run-off into waterways.

Remember – nutrients lost from spreading slurry in the wrong conditions in February and March will be transported to Lough Neagh and other lakes at just the worst time, as the nutrients will promote algal growth in the spring and summer.