Key points

• Optical spot sprayers (OSS) are increasingly being used by growers across Queensland’s Darling Downs and northern NSW
• Benefits include less chemical use, improved hard-to-kill weed control, more chemical rotation options, reduced water use, time savings and reduced weed seed-set
• Other weed technologies include drone-mounted options that use sensors or cameras to detect weeds, creating a map that is used by sprayers for site-specific control

Advances in optical spot sprayer (OSS) technology and other weed control methods are allowing some paddocks to be brought back into successful cropping, while helping to maintain zero or no-till practices.

Paul McIntosh, WeedSmart industry development agronomist (northern region), says advances have been significant for summer and winter cropping programs in northern farming systems.

“Although these sorts of fallow sensor sprayers were around in the mid-to-late 1990s, the accuracy and effectiveness of this newer generation has basically given many landowners their paddocks back.”

OSS uses near-infrared (NIR) sensors mounted on a spray boom to ‘see’ weeds by detecting active chlorophyll. A message is sent to the nozzles, which then spray the weed. This differs from the conventional blanket approach, where the whole paddock is sprayed.

Immediate benefits of OSS are less chemical use, huge improvements in multiple chemical or mode-of-action rotation options, reduced water use as a major time saver when spraying, reduced weed seed-set and a potential reduction in spray drift in sensitive areas.

Mr McIntosh says it is also important to acknowledge that many growers now spray more regularly than in the past. “This is to ensure smaller, easier to control weeds are targeted."

The practice is also helping to manage herbicide resistance while maintaining zero or no-till practices.

“Over the past 25 years, some major herbicides became very economical – dare I say cheap – and led to many of the original sensor sprayers being packed away in lieu of using high-capacity, self-propelled sprayers,” Mr McIntosh says.

“Fast-forward to the present day and we have fallow weed problems, changed weed spectrums and significant levels of herbicide resistance in some species. Plus, the frustrating need to return to more mechanical operations to control tough weeds means our zero or minimum-till programs have been under increasing threat.

“Fortunately, the new generation of OSS has helped overcome our weed problems and while that means another major capital outlay, it is surely one that is on everyone’s purchase list.”

Mr McIntosh says that the popularity of OSS means second-hand rigs are becoming available. “Increasingly, the pioneering owners of these new-age rigs are upgrading for wider and more-effective units, and this means second-hand sprayers are becoming an option for those who decided to wait and see before purchasing a WEEDit or WeedSeeker sprayer.”

Investment

Nonetheless, deciding whether to invest in an OSS can be a more difficult decision than routine machinery upgrades.

Precision agriculture specialist Jeremy Jones from Dalby Rural Supplies says this tends to be because it is a completely new investment and not as simple as, say, a tractor upgrade.

However, he finds that once growers have made the decision, they quickly embrace the new possibilities.

In his experience, most start with a 12-metre WEEDit, a boom-mounted, sensor-based system that can operate day and night and can be used for blanket spraying, fixed-rate spraying or a combination of both.

Mr Jones says that once growers have used them, they often lament their decision not to purchase the 24m or 36m versions. “Or they decide to keep the 12m version and more recently also invest in an autonomous robot to run it. Once they see the value, they upgrade or move towards autonomy.”

Dalby Rural Supplies partners with SwarmFarm Robotics if clients choose an autonomous option.

On Queensland’s Darling Downs, Mr Jones says there has been a huge uptake in OSS. “On the Downs, about 80 per cent of growers are using them. I expect it will some day be the norm, with all sprayers built being optical-spray ready.”

Darling Downs grower Rohan Parkinson, who farms 2800 hectares at Dulacca, has used WEEDit technology since 2017 and is on to his second machine.

He says the decision to invest in an OSS was both economic and agronomic. “We could not kill the weeds and I didn’t want to till. So, I thought, ‘we’ll just have to do it’.”

It is a decision he has not regretted. “I think it’s the single most important thing you could do on a farm. We use less chemical and have effective fallow weed control. The payback period on the WEEDit was less than three years.”

With herbicide costs often one-third of outgoings, he says, any decision to reduce those costs is important. “Especially now with the cost of glyphosate. The current costs of blanket spraying are astronomical.”

St George agronomist Phil Lockwood, from Meremley Agricultural Services, says his clients are noticing increased weed control when using OSS. “And in those 50/50 situations where you’re deciding whether to spray or not, it’s a no-brainer – you go out. Growers are also going out more regularly. This is leading to better control compared to the past and a reduction in glyphosate use.”

Future options

The first boom-mounted sprayers, such as WEEDit and WeedSeeker, are called green-on-brown (GoB) optical spot sprayers because they work in fallow situations. The next step is boom-mounted, green-on-green (GoG) camera-based systems that can be used both in crop and in fallow.

They work by using a camera – either red, green, blue (RGB) or hyperspectral – to record an image. Using machine learning, an algorithm assesses these images, identifying weeds that need to be sprayed. This differs from GoB technologies that use NIR technology to look for chlorophyll.

Jeremy Jones says that because of the extensive artificial intelligence (AI) and machine learning required to do this, commercialisation has been delayed. Early models are specific to weed species and crop type.

Bilberry and John Deere have released commercial systems. Bilberry, the French-based company with an office in Western Australia, has partnered with Agrifac and Goldacres to supply the platforms on which the system is mounted.

John Deere purchased California-based Blue River in late 2017. It operates in a similar way to the Bilberry system but is concentrating on weeds in cotton and vegetable rows.

John Deere has also released its own GoB system called ‘See and Spray’. It is fitted to self-propelled sprayers and is the only factory-fitted system on the market. In a partnership with the University of Southern Queensland, it works via a camera-based RGB system that looks for weeds in fallows, not in-crop.

Another system is the xarvio Smart Sprayer. xarvio™ Digital Farming Solutions, a BASF company, has collaborated with both Bosch and Amazone. The sprayer has not been released yet.

James Cook University is also working on a system called AutoWeed, which is a camera and AI-based system for GoG and GoB spraying.

The competition and applications for this technology continue to develop.  Greeneye Technology, is also using a camera and AI for GoG and GoB. It says it can also detect disease symptoms. It plans to launch in North America this year.

Mr Jones says that despite the excitement about these new technologies, GoG spraying is still evolving and may not prove as popular on the Darling Downs in the short term as the GoB optical spot sprayers. “We are doing such a good job with fallow weeds that in-crop weeds are not as big an issue. We follow the WeedSmart Big 6 Tactics and that’s an effective tool here just now.”

Mr McIntosh agrees, but says it is important to remember that although being able to use a wide spectrum of chemistry has helped put some weeds on the back foot, weeds are survivors. “So, adopting the WeedSmart Big 6 Tactics and ensuring no survivors or stopping weed seed set is valuable advice and a desirable goal.”

Mr Jones says there are also agronomic questions: “Which crops would benefit most from green-on-green spraying? Should the focus be on fallow weed control, and the use of residuals be used pre-planting? Which chemistries are available to achieve the desired results?”

Instead, he believes the future may be investment in more autonomy. “If you have 8000 hectares and a 36m sprayer, that’s a lot of tractor hours to get out there every month. If you could use an autonomous robot, you could gain seven days a month.

“I think the more the industry buys into that, the more development will happen. We have sold seven robots recently for this reason and are filling more orders now.”

Inventive drone solution

After looking at fallow, site-specific weed management options, Coonamble-based grower John Single and his sons Tony and Ben decided to create their own weed detection solution.

Coonamble-based grower Tony Single (pictured) along with his father John and brother Ben created their own drone-based weed detection solution. Photo: Sharon Single

Single Shot uses normalised difference vegetation index (NDVI) to find weeds in fallow. NDVI finds vegetation by measuring the difference between near-infrared, which vegetation strongly reflects, and red light, which vegetation absorbs.

Tony, who chairs the Grain Orana Alliance, says the family decided to build its own unit after researching available options.

“There was nothing on the market – or that we could see coming – that suited our farming system. We wanted a system that quickly and accurately allowed us to map individual weeds on a broadacre scale, giving us the information to prevent and manage herbicide resistant weeds and maintain cost-effective weed control across the farm.

“We operate a 4500ha dryland cropping enterprise. Typical to our area, east of Coonamble, we have heavy clay soils with high water holding capacity. It means fallow maintenance is critical. In a zero-tillage system, sustainable herbicide use is key.”

Working with robotics specialists, Tony’s brother Ben, who is a mechanical and aerospace engineer, came up with drone-mounted Single Shot. It can map 200ha/hour and can pick up weeds as small as four centimetres in size. The weed information collected is processed and a weed map produced. These weed maps can then be loaded into any compatible GPS section-controlled sprayer.

Tony says spot spraying is fast becoming an important part of the farm’s integrated weed management program, while being able to decouple weed mapping from spraying helps with decision-making.

“Firstly, you can look at the map and decide whether you need to spray. Or you can choose how you want to spray – be that as a blanket, a spot-spray or a combination. And you can choose the size of weed you are targeting, with instant feedback on the percentage of the paddock you will be spraying.

“We have found on some occasions there were a lot more weeds in the paddock than we thought, and we were able to make the decision to use a blanket application as opposed to only finding out there are too many weeds halfway through an application with existing technology.”

Knowing how much of the paddock will be sprayed also helps in herbicide choice and rates, managing costs, he says. “As we know the percentage of the paddock to be sprayed, we can choose to use newer, more-effective chemistry in a cost-effective manner.”

Additionally, Tony often chooses to fly over a paddock post-spraying to see if any weeds survived. “Surviving weeds have a higher probability of being resistant. If weeds are detected, I then have a weed map I can use to enact control measures from a different herbicide group.”

Initially, Single Shot was used for standalone spot spray applications, using the farm’s existing 36m Goldacre trailed sprayer, with no modifications needed. Recently Tony has added a dedicated spot spray line to one boom with 18m x 2m sections. This incorporates valves that turn on and off instantly. “This gives us the ability to spot spray and blanket spray simultaneously.”

The sky’s the limit

Tony says the family is still discovering other uses for the technology. For example, it is possible to create a map from multiple passes, detecting every weed. When combined in a map, this information could be used to apply pre-emergent herbicides at the beginning of the next season.

“Or, from a green-on-green perspective, the system has been used to identify large surviving weeds in early growth stage wheat crops, opening up control options that wouldn’t normally be viable on a broadacre scale.”

He also sees possibilities to incorporate Single Shot with autonomous operations. “An algorithm can be used to calculate the shortest path between weeds in the paddock. This could reduce the need for a robot to travel whole paddocks, instead zoning in on where it is needed.

“It will also enable spray drones to be used more effectively, significantly reducing the flight length and spray volume required to cover all weeds as opposed to the whole paddock.”

Other options

Other drone-mounted technologies are also being used and developed, with drones fitted with either an NVDI sensor, for GoB options, or an RGB camera for both GoB and GoG spraying options.

Some drone-mounted options include Goondiwindi-based start-up InFarm, Hardi Geo Select and Single Shot.

InFarm uses a drone to capture high-definition images, which are uploaded into a processing platform that uses a weed-identifying algorithm.

A sprayer ready file can then be uploaded into a standard variable-rate unit and this data controls the nozzles and sections, turning them on and off depending on the presence of weeds.

Hardi Geo Select recently launched a drone to sprayer technology that uses NDVI to identify weeds within a bare paddock. The drone records weeds’ geolocation data, which is put through the software and transferred to the sprayer. It will be released this year (2022).

More information: Jeremy Jones, 0458 626 101, jeremy@dalbyruralsupplies.com.au; Paul McIntosh, 0429 566 198, paul@pulseaus.com.au; Phil Lockwood, 0428 198 573, philliplockwood@bigpond.com; Rohan Parkinson, 0428 955 118, rohan@parkinsonbros.com.au; Tony Single, info@singleagriculture.com.au; WeedSmart Big 6.

Manufacturers

• Bilberry
• WeedSmart - Messina family, Mullewa WA
• Blue River Technologies
• YouTube video - See & Spray - Blue River Technology's precision weed control machine
• John Deere See & Spray
• YouTube video - John Deere Gain Ground with See & Spray
• Amazone Smart Sprayer
• AutoWeed
• InFarm
• Hardi Geo Select
• Single Shot
• Weed-it Optical spot spraying
• YouTube video - Croplands Weed-it Explained
• YouTube video - Weed-it Quadro walk through with Steve Norton.