In an ongoing battle with some hard-to-kill weeds, business partners Robert Eveleigh and Gary Coulton started investigating their options for fallow weed detection and spot spraying on their properties in the Bellata area of northern NSW.

“We could see the advantages of weed detection technology, but neither of us wanted to spend additional hours on a tractor doing a slow and boring task,” Robert admits.

“Choosing a robotic platform for the weed detection and spot spraying technology means we can direct our limited labour resources into other tasks,” he explains. 

The robot’s slow operation speed (9. kmh) coupled with Weed-IT weed detection sensors gives excellent weed control – far superior to blanket spraying with a wide boom, particularly on sloping country.

Being a lightweight machine, the robot also causes far less compaction and is the first machine in use after rain.

“Two of the farms are contoured, and one of those is quite steep. This was the main reason we chose a fixed spray boom rather than a trailing unit on the robot,” Robert says.

“Although the robot has an expect contours setting, which you can toggle on and off as required, we generally prefer to use a slower operating speed when spot-spraying fallow weeds in steeper, contoured fields.”

When inter-row spraying in dryland cotton on these farms, Robert turns on the expect contours setting. Otherwise, the robot can mistake the crop growing on the contour banks as an obstacle.

Robert and Gary grow dryland cereals and chickpea in winter and dryland and irrigated cotton in summer on an aggregation of four properties with a total cropping area of 1400ha.

The dryland rotation usually is cotton, double-crop chickpeas or wheat, summer fallow, wheat or long-fallow back to cotton, giving periods of both summer and winter fallow to store soil moisture and drive down the weed seed bank using the spot sprayer.

The main fallow weeds are barnyard grass, feathertop Rhodes grass, fleabane, peachvine and sowthistle.

They decided to fully automate with a high-clearance Swarmbot on 3m wheel spacing mounted with a 12m RBE boom coupled with Weed-IT Quatro sensors, and a 1500L tank.

They took delivery of their spot-spraying unit, Conan, in September 2023, and in the following 12 months, Conan clocked up about 1500 engine hours doing fallow and cotton inter-row spot-spraying across the four farms.

Barnyard grass and feathertop rhodes grass are their most difficult-to-control weeds, both of which have a high tolerance of, or resistance to, glyphosate.

Robert uses the robotic spot sprayer to apply the double-knock tactic to target these weeds.

The first knock is glyphosate (Group 9) mixed with haloxyfop (Group 1, Verdict) at the registered higher optical sprayer rates, followed by paraquat (Group 22) as the second knock. They also use a broadacre application of metolachlor (Group 15) to target these two grasses during the long fallow ahead of cotton.

Going into cotton, Robert usually does a broadacre application of residual herbicide, such as diuron (Group 5) or terbuthylazine (Group 5, Terbyne), then follows with Conan spot spraying to kill any weed escapees.

Since moving to automated weed detection, they have used 70 per cent less herbicide in their fallow weed management and expect their herbicide use to reduce even further due to the flow-on effect of driving down weed seed numbers.

Automated spot spraying is a valuable tool in the WeedSmart toolbox to reduce the risk of herbicide resistance in weeds through timely application on small weeds and reduced weed seed set.

“We have just added a fence-line kit to the spray boom which allows us to spray along fences and to spray right up to the base of other obstacles such as power poles,” Robert said.

“Being able to consistently spray these non-crop areas will reduce the encroachment of weed seed into the crop area.”

Robert and Gary manage the farms without additional labour, so with the robot doing most of the fallow spraying, their workload has reduced significantly.

“While the robot is spraying, we can focus on planting cotton, harvesting wheat or even recreation,” he said.

“It’s like having another person working full-time on the farm.’

“Now the mapping is complete, and we are confident the robot is operating as we want it to, we just need to check it each morning and fill it as required.

“It is a great feeling to drive away knowing the robot can take care of itself during the day, only spraying when the conditions are right.”

The onboard weather station prevents Conan from operating when wind conditions or temperatures are unsuitable for spraying.

Under adverse conditions, the robot will go into ‘sleep’ mode until the weather improves. They hope Conan will soon connect with the local WAND tower to further enhance the robot’s ability to detect conditions that increase the risk of spray drift.

One feature Robert is keen to see added to the platform is onboard rain detection.

Apart from viewing the field through Conan’s CCTV camera, there is no way to determine how much rain has fallen. If a storm passes overhead, the robot will continue working, and because Robert lives away from the farm, he is often unaware of isolated storms or showers at the farm.

Although their irrigation area is relatively small, Robert and Gary would eventually like to use the robot to spot spray there as well.

Conan has 3m wheel spacing, which suits their dryland cropping, but the irrigated area is set up on 2m spacing, so the expansion will present some challenges. Wingtip lift for irrigation, dock and refill capability, and precision planting are all features Robert and Gary are keen to adopt as they become available.

For more information about automated weed detection go to www.weedsmart.org.au