The precise application of slurry had long been a focus of attention before the current explosion in the price of fertiliser, an event which has certainly invigorated interest in its efficient use.

Cost aside, there is the growing realisation that phosphate (P) and potash (K) resources are not infinite, and so better use is going to be have to be made of what is already available.

Slurry as a resource

Nitrogen may be abundant in the atmosphere, but it takes a good deal of energy to convert it to a useable form, so that too has limits on its use, which are mainly set by energy prices.

Abbey vacuum tanker slurry — Getting nutrient rich animal waste back on to the field has become far cleaner and more orderly over the years

Slurry is rich in all three of these basic nutrients so getting it applied evenly and at a known rate is essential if it is to be considered a fertiliser in its own right, rather than a waste product to be disposed of.

Up until recently, the ubiquitous splash plate slopped it on the ground in a rather indiscriminate fashion which wasted a good deal of the nitrogen and annoyed the neighbours.

With the advent of ground level application, it is at last possible to apply the material in a much more disciplined fashion and this has been enhanced further by the addition of flow meters which precisely record the amount delivered and where.

Click on the video below to get a glimpse of the spreader in action during Agriland’s visit to Lyons Farm.

The next step is to not only record the quantity delivered but actually control the rate at which it is applied, as would be the case with any other fertiliser.

This is now now achievable on all new tankers, and many older ones, with either a dribble bar or trailing shoe boom according to Grasstec, which is promoting its latest flow monitoring and control system.

One early user is University College Dublin (UCD) which took delivery of a 3,000 gallon Abbey twin-axle vacuum tanker late last year.

The opening of this year’s slurry spreading season has seen it being put through its paces as the college farm explores its potential.

Accurate application of slurry — GPS makes possible the neat alignment of bouts

No longer the wallflower

Abbey has a reputation for forging ahead with the development of the humble tanker and elevating it to the status of specialised nutrient applicator.

In this pairing with a Muller Flowmeter system from Grasstec, the vacuum tanker has taken another step forward and the college is now able to record just how much slurry has been applied, when it was applied, and where.

Flow meter on vacuum tanker — The flow meter and control valve sit high on the side of the tank

This information is then recorded in the cloud-based farm management software and so is available to all with permission, to access the the data.

In the case of the college this group not only includes the farm manager and tractor operator, but also academics who may be involved in research projects which could be influenced by the application of slurry.

As convenient as this may be, there are many other benefits to the system, including the ability to prevent the slurry being placed where it shouldn’t, especially alongside water courses.

ISOBUS connection on Abbey vacuum tanker — Tanker and tractor are connected by standard ISOBUS plug

In addition, the tanker will only work in those areas that are to have slurry applied. If the tanker finds itself in the wrong field, the valve won’t open and the liquid stays in the tank.

These parameters may be easily changed from a mobile app or other device linked into the database, enabling a slurry application plan to be constructed and regulated from the office or tractor cab.

Exact amounts

However, the major advantage is that the rate at which the slurry is applied can be altered in real time as the tractor moves across the field.

The Muller flowmeter has no moving parts to wear or jam. It works by measuring the conductivity of the slurry against its inner lining, meaning that it will not block the feed pipe.

Flow meter grasstec trimble slurry — A combination of GPS steering guidance and metered flow, results in accurate placement of the slurry

By placing an infinitely variable valve immediately downstream of the flowmeter, the amount of material passing through can be regulated automatically.

Thus, as the tractor’s speed varies, so does the rate at which the material flows into the macerator for distribution to the booms.

It will also means that in future, different rates can be applied in different areas of the field, based on prescription maps or other previously collected data.

Nitrogen regulation

Although not fitted to this unit, it is also possible to attach an NIR sensor which measures the nitrogen content of the slurry and adjusts the flow rate to apply the desired quantity of this important nutrient.

Currently, the college calculates the desired application rate by reference to the analysis of the slurry in the collection tanks. It is considered a reliable indicator as all the tanks are thoroughly mixed before emptying.

Flowmeter with valve — A nitrogen sensor is a further option which can be fitted to control the flow valve

Mapping the yield is somewhat more problematic as the fields are grazed as well as cut for silage, so this important figure can only be estimated at present.

Ian Kealy, farm machinery manager at UCD Lyons Farm, notes that the Grasstec system, which marries the Muller flowmeter to the Trimble GPS installation, should not be considered as just another bolt-on attachment to the tanker.

Instead, he sees the encroaching digitalisation as an opportunity to install each tractor and implement as a component of a much more tightly managed enterprise – the tanker as an extension of the network, not vice versa.

The hardware

The matching of an Abbey Machinery tanker to the latest software is a natural progression for the Co. Tipperary-based manufacturer has rightly assumed that slurry application will become ever more closely managed and regulated in the future.

This decision has led to the company providing well equipped machines which offer standards of efficiency and safety for others to match, although none of it comes free.

The model in use has a trailing shoe boom, with adjustable ground pressure, fed by a Vogelsang macerator rather than distributor head. Turnaround time in the yard was quick, helped by the storage tanks being full.

Abbey tanker steering rear axle — The steering rear axle greatly enhances the ability to negoiate tight corners.

The rear axle steering saw it comfortably cope with confined spaces while in the field it could be turned tightly on the headlands without digging up the sward.

The flow meter and valve are installed on the suction line which takes the liquid from the centre of vessel rather than rear. The control unit was placed in a sturdy box, attached to the front of the chassis.

One small criticism of Ian’s was the lack of a pressure gauge that could be read from the cab. Although it might be argued that it was no longer necessary, he did miss the reassurance of a large dial connected directly to the tank.

Looking ahead

Bringing digital management aids to farming is an incremental process. We are repeatedly presented with visions of the future where everything is in place and all is running smoothly, but arriving at that apparent paradise is a long trip.

This journey is one of many steps and the college farm has taken several of them with the Grasstec equipped Abbey tanker. Precisely placing and mapping the addition of nutrients to the soil is important, but it is only one half of the equation.

Trimble UCD Kealy — L-r: Ian Kealy of UCD, Grace Sweetman and John Grainger of Grasstec

To complete the picture there will also need to be some record of the effect that those nutrients are having on yield. Unfortunately, this is problematic when the fields are grazed, as sheep leave something to be desired as accurate yield monitors.

However, input levels can now be more accurately targeted and their application be more consistent, which removes a large degree of uncertainty from any results upon which management decisions may be made.

Vantage Ireland

The Trimble GPS equipment and Muller flowmeter are supplied by Vantage Ireland who are the sole agents for these brands in Ireland. Vantage Ireland is a wholly owned subsidiary of Grasstec of Co. Cork.

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