Aware of the dearth of options for tackling pernicious grassland weeds without clobbering clover, Charlie Murray went in search of a solution.

The core of his Clyde Agriculture business, which he runs with wife Irene, is providing high-grade grass and herbage seed mixtures to livestock farms throughout the UK.

And having witnessed his customers spend thousands creating diverse swards, only to degrade them when tackling weeds, he thought there must be a better way.

See also: Ecorobotix spot sprayer slashes chemical costs by over 90%

A breakthrough occurred a few years ago when he met Colin Taylor from SoilEssentials.

“From that point I was aware that credible spot-spraying technology was out there and I felt it would be an important service to offer our customers,” says Charlie.

Then, having seen the firm’s Skai machine at the Royal Highland Show in 2023, he was convinced it was the way to go.

The final job was to run it past local contractor Alistair Brown, who was happy to provide a tractor and operato.

The system arrived in early 2024 attached to a 12m Team sprayer, accompanied by a gang of SoilEssentials experts who quickly got it up and running.

Currently, docks are the only grassland weed it can tackle, but more undesirables will soon be added to its repertoire.

Information is translated into application maps © James Andrews

High-definition cameras

In simple terms, it works thanks to five high-definition cameras – four on the boom and one on the front of the tractor – which identify individual docks and signal the relevant nozzles to apply the chemical.

The sprayer itself is fairly standard, apart some high-spec options such as boom recirculation and individual nozzle control – the latter provided by ultra-fast Gevasol solenoid units that open in just 0.1sec.

But it’s behind the scenes where the really clever part takes place. Embedded in the software are artificial intelligence models that have been “taught” by SoilEssentials’ engineers to recognise weeds.

This process involves showing it thousands of pictures, until it is able to reliably identify the target.

When in use, the system carries out its identification in a fraction of a second, placing a box around the weed and assigning it a GPS reference.

These co-ordinates are then used to make sure the relevant nozzles are switched on at precisely the right time.

The positioning signal comes from a GPS receiver built into the Skai hardware, which connects to satellites that don’t require a subscription.

These give perfectly acceptable results, but it is possible to achieve still higher accuracy when taking a feed from a tractor that’s running on RTK.

Charlie Murray © James Andrews

Testing the accuracy

Charlie drove the sprayer himself for most of last season so that he could get to grips with the system and monitor how well it was working.

“As the tractor [a New Holland T6.180] is running on autosteer I had plenty of opportunity to look around and assess how it was performing,” he says.

The process was made easier thanks to a detailed screen in the cab which has bar charts displaying spraying activity.

“These give the operator confidence the system is working properly, particularly the section behind the tractor.”

To further assess efficacy, dye was often added to the tank to improve visibility of the application process from the cab.

As the system goes about its dock-hunting business, it issues each of the weeds it identifies with a percentage certainty.

Generally, the machine is set to spray those with an 80% rating or higher, but the parameters can be tweaked if necessary.

On top of this, it produces detailed application maps which are uploaded to SoilEssentials’ Kore cloud-based precision farming platform.

These can then be used to track weed populations over time, which should hopefully decline with the use of the system.

Precise timing

The sprayer achieved a very high success rate all season, only being outsmarted by the odd curled dock in the early days.

However, by taking pictures of these that developers could add to the programme, accuracy was soon improved.

Timing is also critical for getting the best from the system.

“There is always enthusiasm for controlling docks in May, but this can be a tricky time in the season as there are cool nights and a risk of light frost that can limit the translocation of the chemical to the roots,” says Charlie.

“Waiting until later in the year can sometimes offer more favourable weather conditions, and better weed control will be achieved if application takes place following a cut of silage or on topped grazing land.”

Another challenge is ensuring docks are at a suitable stage for spraying, as they need to be prominent enough for the system to identify them.

“Heavy canopies of grass and clover can impair camera vision and therefore affect performance,” he says.

Nozzles are triggered by the control system © James Andrews

Chemical savings

A secondary benefit of treating only weeds is a dramatic reduction in chemical use.

The maximum proportion of a field Charlie sprayed last season was 37%, but 10% was more common and it was sometimes lower than 5%.

Thanks to this reduction, his customers always have a lower overall bill than would be the case if getting a contractor to spray the whole field conventionally – the average being slightly more than half the cost.

In addition, grass is healthier and the targeted removal of docks helps further improve yield.

“A 1% infestation of docks equates to a 1% grass yield loss – so a 3.75ha sward yielding 10t of dry matter a hectare with a 5% dock population would lose sufficient yield to feed a 650kg cow for 180 days,” says Charlie.

Teething problems

Despite its complexity, Charlie only had one problem with the system last season, which appeared to be triggered by some very bright, low sun.

Instead of picking up the docks it decided to target everything else in the field.

But the problem was soon solved as a team from SoilEssentials came out, rebooted the software and had it up and running in a couple of hours.

“Support is essential for complex systems like this and SoilEssentials has been great on that front,” he says.

Maintenance is also minimal with just the camera lenses requiring a daily wipe with a microfibre cloth.

That said, dirt build-up isn’t excessive as there are covers which are fitted when not in use.

Next steps

With one season under its belt, Charlie is confident of the tool’s dock finding abilities.

Plus, the fact that the system records extra images as it works, which are then sent to SoilEssentials to add to the model, means accuracy will only improve.

Thistles are next on the hit list and he’s put some time into gathering pictures to get this up and running.

For this work, the machine is put into a specific image gathering mode and he drives across the field while it records.

“After that, I think rushes would be my main priority, and perhaps nettles.”