CAFRE Slurry Spreading Demonstrations

Slurry from housed livestock in N. Ireland contains valuable sources of plant nutrients in the form of Nitrogen, Potash and Phosphate.  On average 9000 litres (2000 gallons) of dairy cow slurry has a total nutrient content of approximately 27 KG of N; 11 KG of P; and 29 KG of K. At current fertilizer prices, these nutrients in every tanker load are worth £65.  However, the method and timing of slurry application are two factors that determine the utilization efficiency of these nutrients by the growing crop.  Spreading slurry during the growing season, using equipment such as a Trailing Shoe can improve the utilization of slurry nitrogen.  

Over 400 farmers have recently attended ten on-farm Trailing Shoe demos.  They were able to see first hand the benefits of using this technology under Northern Irealnd conditions.  The benefits include:

Many of the benefits listed above ease the management of slurry spreading on farm, but are difficult to quantify financially.  One benefit that is readily financially quantifiable is the potential for saving fertilizer use through the improved nitrogen utilization from slurry.

Research at AFBI, Hillsborough has demonstrated that spreading slurry using a Trailing Shoe slurry tanker almost doubles the utilization of slurry nitrogen compared to conventional splash plate spreading.  The resultant saving in nitrogen fertilizer costs is worth up to £35 per hectare per crop of grass silage where slurry is applied at a rate of 50m³/ha (4500 gal/acre).

Trailing Shoe spreading technology has been adopted as a management policy at Greenmount Campus, CAFRE to increase nitrogen utilization from slurry and reduce fertilizer costs.  Fertiliser savings on the 180 cow Dairy Unit 2008 are expected to be up to 10 tonnes of 27 percent Nitrogen at a cost of over £3,000.

The research trials conducted at AFBI, Hillsborough, indicate yield benefits from trailing shoe slurry application up to three weeks after the silage harvest.  AFBI researchers have not observed any detrimental impacts on the quality of silage made from the ensiled grass re-growth.  This wider window of opportunity also applies prior to first cut silage in March or early April when farmers would traditionally have been reluctant to apply late slurry applications to silage swards where there was a good grass cover.

Most trial work has been carried out at relatively high application rates, typically 50 m³/ha (4500 gal/acre).  With conventional splash plate application, most dairy farmers would restrict application rates to less than 50 percent of these levels between silage cuts.  The trailing shoe spreading system therefore gives heavily stocked farms the opportunity to apply greater quantities of slurry during the growing season resulting in improved nutrient utilization and savings in fertilizer costs.

As indicated above, dairy cow slurry has a high content of potash (K).  Given the high rate of removal of potash from the soil by heavy crops of grass harvested for silage, the recommended CAFRE practice is to apply the majority of slurry on swards destined for silage harvesting to replace the potash removed by the crop.  However, where enough slurry is available, 17m³/ha (1500 gal/acre) each year will maintain the P & K level of soils analyzed at Index 2 along with straight nitrogen fertilizer.

Trailing shoe slurry spreading equipment deposits slurry on the soil surface in narrow bands about 50 mm (2”) wide.  By comparison, with conventional splash plate spreading the slurry is spread across the complete sward surface.  Trailing shoe spreading reduces the exposure of slurry to the air.  This reduces ammonia volatilization resulting in improved slurry nitrogen utilization. The reduction in ammonia volatilization also means a reduction in the level of smell associated with slurry spreading.  Combined with the slurry deposition on the soil surface, the reduced visibility and smell from slurry spreading operations should help improve relations between farmers and other rural dwellers!

Research studies to date have proven that the Trailing Shoe slurry spreading technology has many benefits to offer.  These include improving slurry nitrogen utilization and widening the spreading window during the growing season.  Ongoing research studies into the technology at AFBI, Hillsborough indicate that repeat applications of slurry by trailing shoe do not have any detrimental impact on sward persistency and grass quality.

CAFRE staff would like to thank all the host farmers who kindly made their facilities available to us. Without your cooperation, these events would not have been possible.

Trailing Shoe Slurry Spreading Demonstrations - Summer 2008

Trailing Shoe Slurry Spreading Technology

Over 400 farmers have attended demonstrations of Trailing Shoe Slurry Spreading at ten venues across Northern Ireland in recent weeks