Alert: Farmers warned to spread slurry 'very carefully', as water is affected nationally

The spreading of fertiliser is impacting water quality around Ireland, with advice from a semi-state government body now issued to farmers.

Agriculture organisation Teagasc has said that the loss of nutrients, phosphorus (P) and nitrogen (N), to water from fertiliser application is primarily to blame for poor water quality in Ireland.

As the slurry spreading season opens across the country over the coming week, it is "very important" that farmers and agricultural contractors apply slurry "very carefully", so as to prevent nutrient losses to water.

* Slurry is a valuable fertiliser:

Slurry is a valuable source of nutrients on the farm and can benefit grass and crop growth when applied correctly. At current prices for nutrients, applying 1,000 gallons of slurry @ 6% DM to grass is equivalent to a 50kg bag of 9-5-32 fertiliser when applied by LESS and is worth €29 per 1,000 gallons. Where possible slurry should be targeted at fields at index 1 or 2 for P and K to maximise its benefits.

* Regulatory requirements when spreading slurry:

In Donegal, the open period for spreading slurry is February 1. Farmers are asked to make slurry contractors aware of any water features that may be present in the fields that slurry is being applied and to ensure that slurry is kept back the correct distance.

For the first two weeks following the opening of the spreading period it is important to note that slurry must be kept at least 10 meters away from rivers, streams, watercourses and drains and reverts to 5 meters once this time period has elapsed.

When spreading slurry, it is also important to remember that weather and ground conditions can have a significant impact on nutrient being lost to water.

Spreading slurry on fields that are frozen or snow covered, waterlogged, flooded or likely to flood is prohibited by the regulations. The reason why it is prohibited is that adding slurry to fields under these conditions greatly increases the likelihood that the nutrients from slurry will be lost to water either by over land flow in the case of saturated soils or by leaching to ground water in free draining soils.

When ground conditions are suitable, it is important to check the weather forecast as slurry should not be spread when heavy rainfall is forecast as this can also lead to soil saturation and nutrient losses.

* Best practice advice when spreading slurry:

While many farmers will be able to hold off on spreading slurry until later in the spring when conditions are more suitable, others will need to spread slurry due to tanks being full.

Farmers that find themselves under pressure to spread slurry should examine if they have enough slurry storage in place or if there is clean rain water entering tanks and impacting storage. Ask your advisor for help with this and take action if there is a shortage.

* Farmers should also consider the following:

1. Timing:

Farmers need to be aware of weather conditions when applying organic fertilisers. When organic fertilisers are applied to soils, this has a large influence on the uptake of nutrients by plants and the potential for losses to waters. A consistent soil temperature of 6˚C and preferably rising will mean that grass is growing and has the potential to take up the nutrients applied.

Another essential factor is the soil moisture content. Is the soil saturated or can tractor work occur without causing structural damage to the soil? Soil that is close to or at saturation point will lead to surface water runoff if additional rainfall is likely to occur.

Checking the soil moisture content of the field and the weather forecast is important prior to applying organic fertilisers. This is especially important when using the umbilical slurry spreading system. 

This system is particularly high risk to water quality if used incorrectly, as it allows slurry to be spread when a slurry tanker wouldn’t be able to travel on land due to ground conditions. While this system does reduce soil compaction, it should not be used on saturated soils as it would pose a risk of nutrient loss to waters.

2. Location:

The fields that slurry is going to be applied to - should be chosen carefully. These should be the fields that have a requirement for P and K and with a good pH.

They should also be the drier fields on the farm, ideally with no drainage system in place and away from streams and rivers.

Fields that have high connectivity to the drainage network or fields with critical source areas (CSAs) should be avoided until later in the spring to lower the risk of nutrient loss to water. 

3. Rates:

It is important to match the rates of application of organic fertilisers to the growth rates of the grass/crop. This is especially important in the early spring period where growth rates are at their lowest.

Applying slurry at rates greater than crop demand means that nutrient is available to be washed away into the drainage network or leached to groundwater. Lower application rates of organic fertilisers are recommended in early spring.

Summary Points:

* Slurry at 6% DM applied by LESS is worth €29/1,000 Gallons and contains 
* Farmers should assess their slurry storage facilities to ensure that they meet the minimum storage requirements for their county
* The open period for slurry spreading in Co. Donegal is February 1, 2024 
* For two weeks following the opening of the spreading period slurry must be kept at least 10 meters away from rivers, streams, watercourses and drains (including dry drains) - This reverts to five meters once this time period has elapsed
* Slurry cannot be spread on fields that are: frozen or snow covered, waterlogged, flooded, if heavy rain is forecast within 48 hours
* Maximise the nutrient content of slurry by spreading when: Soil temperatures are at 6˚C and rising, soils are trafficable and are not saturated, slurry is targeted to drier fields with a requirement for P and K and have a good pH
* Avoid applying to fields that are highly connected to the drainage network of the farm, critical source areas (CSAs), until weather conditions are favourable
* Application rates of slurry must match growth rates of the crop