Low Emission Slurry Spreading –Delivering for Farmer and the Environment

Eddie Webb, B&T Soil & Environment Adviser, Teagasc Galway/Clare

The permitted period for spreading slurry in Galway/Clare is 16^th January. Slurry has becoming an increasing valuable resource on farms especially in light of continuing increased fertiliser prices. The traditional method of spreading slurry by means of slurry tankers with splash plates is being replaced by low emission slurry spreaders (LESS).  The new nitrates regulations have resulted in a phased introduction of LESS on farms as set out in table below. This requirement will result in slurry being spread by LESS becoming more prevalent on farms with the Climate Action Plan having a target of 90% in 2027.

The main environmental and monetary benefit to farmers is the reduced loss of ammonia during slurry spreading with agriculture being responsible for 98% of all ammonia emissions. Ireland has failed to reach it ammonia emissions targets in recent years. Ireland’s 20230 emission target ammonia can be achieved through the full implementation of ammonia reduction technologies including LESS and protected urea fertiliser. 

Nitrogen in the form of ammonia is lost from organic manure when they come into contact with air, particularly on warm or windy days. The more nitrogen loss as ammonia, the less effective the manure will be as a fertiliser.  There is an increasing need to reduce ammonia emissions to prevent damage to sensitive sites, to protect human health and to improve the efficiency of nutrient use.

LESS increases the Nitrogen recovered from slurry compared to splash plate where losses are high due to weather, wind and the sun. Teagasc research has found that loses in the form of ammonia can be reduced by 60%. The main loss is by volatilisation and LESS technology reduces the surface area to which slurry is applied and puts the slurry directly on the ground/soil.

As highlighted above, LESS will give an extra 3 N units/acres compared to the traditional splash plates when spread at 1000 gallons/acre. In financial terms this will translate into additional gain over €10/acre when slurry is spread at 2000 gallons/acre.  Another additional benefit is with LESS is the lower level of contamination and faster recovery of grass/silage swards. This gives farmers the flexibility of choosing paddocks without worrying about poor cleanouts after grazing.

Slurry spreading should be targeted to those fields which have the highest requirement. Cattle slurry is a good source of P and K fertiliser and should be applied to parts of the farm that have either low soil P or K levels or to silage fields that have a high requirement. Soil analysis on farms have shown that fields located far from the farmyard are typically lower in soil P and K as they receive lower applications of slurry. Silage fields tend to be located furthest away from the yard and often have low soil fertility levels, as well as the largest demand for both P and K. The fertiliser value of slurry has increased in line with increased fertiliser prices which may offset the extra transport costs incurred in spreading to fields located further away from the farmyard.

In summary farmers should target slurry where there is the greatest need. Farmers should preparer and implement a nutrient management plan to ensure the nutrients are targeted where they are most needed. Slurry spreading should be avoided where heavy rain is forecasted within 48 hours The buffer zones to be adhered to when spreading slurry include :

• 5m of surface waters (extending to 10m in the first two and last two weeks of the spreading season)
• 10m of surface waters where the slope towards water exceeds 10%
• 15m of exposed cavernous or karst features, such as swallow holes and exposed rock
• 20m of a lake shoreline
• 25-200m of a water abstraction point for human consumption