The many benefits of slurry separation

Slurry separation is becoming increasingly popular on beef farms, as changes to nitrates rules drive many farmers to look at slurry management options other than obtaining more land or reducing livestock numbers.

Slurry separation can allow for a more targeted use of organic nutrients on farm while offering a cost-effective transport option where manure is being exported off farm.

It is not a new technology. Over 30 years ago, during the farm manager phase of my career, it was an integral part of slurry management on the farms I ran. At that time, there were no restrictions around slurry storage, nutrient management plans and spreading dates.

The process involves the separation of slurry into solid and liquid forms. The mechanical separator removes the larger fibre particles from the liquid.

The remaining liquid slurry will have a lower dry matter and should not need agitation before spreading on the land.

Raw cattle slurry will typically have a dry matter of 7-10pc, while the liquid slurry is generally at 4-6pc. It is also lower in volume, which allows for better utilisation of slurry storage.

As the slurry is more liquefied it will percolate into the soil more readily than normal slurry, so it is exposed for less time and the risk of ammonia losses to the atmosphere are reduced.

Slurry from intensively fed beef cattle is a high-value manure due to its nutrient content.

If separated, the liquid material can also be used as a top dressing for cereal crops, provided it is applied at the correct growth stage and weather conditions are suitable.

While modern spreading techniques such as dribble bar and trailing shoe have greatly improved efficiency in terms obtaining maximum crop results from slurry, it is a bugbear of mine to see slurry residues returning in silage clamps at time of harvesting, particularly after dry spells.

This organic material will affect fermentation, reduce mineral absorption by the animals and lead to an increased mycotoxin risk. Separation of fibre particles from liquid slurry decreases the likelihood of slurry residues remaining at the base of grass plants.

The separated solid material will comprise around 25pc of the total slurry volume, depending on slurry type, animal diet and separation technique.

It can be stored and then spread on land, similar to farmyard manure. This material fits perfectly with tillage rotations, forage maize, horticultural crops and grass reseeds.

This solid component can be easily transported to farms with a requirement and ability to import organic manure.

With the ever-increasing cost associated with straw bedding and the limited availability of alternative bedding options such as peat, woodchips and miscanthus, some farmers have explored the use of this separated solid material as a green bedding solution.

It needs to be at the higher level of the dry matter range (in excess of 35pc) and is really only suitable for bedding yearlings and mature cattle.

It has been a widely used option on intensive dairy farms in Northern Ireland for 25 years as a dressing option for cubicle beds.

A number of beef units have also started using this material as a bedding source, prioritising straw for feeding and for bedding younger stock.

For those who have bedded cattle with peat or woodchips in the past, the solid separated material will act in a similar fashion. An initial bedding depth of 10-15cm is advised with a top dressing every two weeks.

The design and operation of separation equipment is part of a suite of practical solutions to one biggest issues facing the livestock sector.

Hopefully in time this equipment may be eligible for grant funding and become a realistic slurry management tool on many livestock farms.