Slurry has swiftly moved from being considered a nuisance, to becoming a resource that will reward careful management as herd sizes grow.

The restrictions surrounding its storage and application become ever tighter.

In Ireland we have our own industry catering for both farmers and contractors and in many ways it is hugely successful, exporting to many countries around the world, as well as supplying the home market.

Scaling up

Yet, as good as we are at satisfying the demands of farmers here with suitable equipment, there is, on the continent, an industry that is another level due, in the main to the large number of anaerobic digestion plants.

Slurry nurse tanker — Road going nurse tankers are common on the continent , this one relies on a centrifugal rather than a rotary lobe pump for filling.

With the much larger volumes and bigger fields than those found in Ireland, manufacturers do not suffer the same constraints of size, and so the machinery can be correspondingly bigger and more expensive.

Slurry spreader at Agritechnica — Based on a Claas Xerion this self propelled tanker Zunhammer is kitted out with a Vogelsang pump and macerator unit

It might be thought that large scale continental machines are hardly relevant to Ireland, but there are some engineering principles involved which could well be worth taking note of.

Filling the tanker is perhaps the most fundamental difference, on the continent it all all done by a pump, relying on suction alone is simply not fast enough and does not always result in full tank, especially if drawing from a low level.

Slurry handling installation on tanker — A typical installation on a large continental slurry tanker includes a positive displacement Vogelsang pump (right) with combined stone trap and macerator (left)

Positive displacement pumps, usually of the rotary lobe variety will fill tankers much more quickly and completely than vacuum pumps, and these are employed on a near universal basis-to-fill, macerate, agitate and distribute the slurry on the larger equipment.

However, they are prone to wear and regular servicing may be required, especially if the slurry is at all abrasive or viscous, so the vacuum pump is not entirely redundant just yet.

Product application

Once in the tank there is usually the option of agitation during transport and this too is a job for the pump, some slurries are prone to settling and this is to be avoided if a consistent application rate of nutrients is to be achieved.

For applying the product there still the basic options of dribble bar, trailing shoe or injection, there was no sign of any such thing as a splash-plate at Hanover, they are now consigned to the dustbin of history.

Slurry injection unit by Volmer Engineering — Volmer Engineering of Germany produce this slurry injection unit for attachment to the rear of tankers

It was Vogelsang who made the news with regards to application, as the company took the opportunity to show in public for the first time.

It’s latest boom can be operated at width between 21-30m, thanks to its combined telescopic and folding actions.

Known as the Vogelsang Blackbird 30m, there was room enough for just half the total boom width on the stand; 30m is a good stretch for a set of heavy slurry booms.

To put it into context, that is four times the width of a standard 7.5m boom, as is commonly found on Irish tankers and therefore requires four times the feed volume, while covering the same area in a quarter of the time.

Pipework on slurry boom — The boom structure on the Vogelsang Blackbird doubles as the units pipework

Weighing 5,800kg the the outlet spacing at maximum width is 25cm which entails dragging 120 shoes across the ground, this unit will need a serious number of horses in front of any tanker it is mounted on.

Adjusting the working width is a combined function of folding tips and telescopic adjustment of the arms. When folded, the supply of the slurry to the unused outlets is cut off by inflatable bladders within the pipe, a feature which lends itself to a certain degree of section control.

Slurry distribution head — Flow between the distributer head and the trailing shoe outlets is controlled by internal bladders supplied by air via the blue pipes shown

There are four distribution heads – two on each boom, and they are fed through the support arm itself, which acts as a pipe as well as structural member. With this degree of complexity, it is essential that the slurry passes through a macerator on-loading, to ensure that no foreign bodies find their way out to the pipework.

Unblockable simplicity

Rotary distributer head type booms do involve a lot of pipework and mechanical features that can block or malfunction. A Swiss company, Swisstec Ag, has come up with an alternative boom system that involves no moving parts other than the hinges and rams to unfold it.

Slurry boom at Agritechnica — A completely different approach is taken by the Schleppfix distributer from Switzerland

Known as the Scleppfix, it consists of two manifolds which the slurry is delivered under pressure in the conventional vacuum tanker way.

As it enters the chambers, it strikes a veined plate which directs it evenly across the width of the manifold from where it flows down to spouts attached to the lower edge.

It is claimed to be blockage free, as there are no smaller apertures for the slurry to pass through. It is nether a dribble bar or trailing shoe as commonly recognised, but a combination of both.

GRP slurry tanker — A further route to saving weight is by the the use of a GRP tanker, This Annaburger unit weighs in at 3,500kg without rear attachment

Should it find it ever find its way to Ireland, then there must be some question mark over its eligibility for TAMS grants.

It parts the grass and lays the slurry on the soil surface, as is required by a trailing shoe, but the Department of Agriculture, Food and the Marine (DAFM), might quibble about the potential for ammonia evaporation as it passes through the manifold.

Unfortunately, quite how it will be decided as to whether this may, or may not, make it eligible for TAMS is shrouded in the mists of bureaucracy, making it’s importation into Ireland risky.

Slurry separation

Separating the liquid and solid factions of slurry is usually undertaken as a measure to reduce its storage requirements, yet it was also claimed at the show that it separates the nitrogen from the P and K, allowing the two factions to be considered as two distinct nutrient sources.

Unfortunately, it appears the balance of P and K between the liquid and solid portions depends on several factors, not least of which is the pH of the slurry, so, for now, it should remain only an interesting idea.

Lorry with separator — This mobile separation unit can process up to 200 cubic metres of slurry an hour

However, great caution need also be taken when considering nitrogen levels in slurry for the analysis of any particular sample can fluctuate widely between labs for many reasons, which is why Near Infra Red spectroscopy (NIR) is being touted as the way forward.

NIR sensors on slurry tankers are able to detect nitrogen levels in real time and adjust the flow to ensure a consistent application rate; P and K application rates will then be subject to nitrogen content, which is not ideal, hence the suggestion that slurry separation might go someway to overcoming this.

Schleppfix

Slurry management comes of age at Agritechnica 2023