Trial chips away at weed challenges

Trial chips away at weed challenges

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The Weed Chipper couples the age-old chipping hoe approach with modern optical weed detection technology and mechanisation to create a non-herbicide tactic to tackle herbicide resistant weeds of any size.

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Drone shots showing a commercial paddock prior to treatment with the Weed Chipper (top) and the soil divots after weed control treatment (bottom). Photo by AHRI.

Drone shots showing a commercial paddock prior to treatment with the Weed Chipper (top) and the soil divots after weed control treatment (bottom). Photo by AHRI.

RESEARCHERS have put the world's first site-specific mechanical weeder for large-scale grain production systems through its paces and proven that it can effectively control weeds in fallow situations.

The Weed Chipper couples the age-old chipping hoe approach with modern optical weed detection technology and mechanisation to create a non-herbicide tactic to tackle herbicide resistant weeds of any size.

Herbicide resistance weeds are challenging conservation cropping systems, especially with the rise of glyphosate resistance affecting fallow and pre-seeding weed control options.

Like the optical sprayers that have vastly reduced chemical usage over the past 20 years, the Weed Chipper is fitted with sensors that detect weeds and trigger individual tynes, instead of spray nozzles, to rapidly chip out the weeds.

University of Sydney associate professor and director of weed research Michael Walsh said Australia has had an unfortunate habit of claiming world-firsts in the extent and severity of herbicide resistance.

"Fortunately, we have also been leaders in the development of new tools to help combat the problem," Dr Walsh said.

"The Weed Chipper ticks the conservation cropping box, causing minimal soil disturbance in commercial-scale evaluations.

"With the field trials completed and a commercial partner found, the Weed Chipper concept is ready for fine-tuning with designer sweeps to maximise weed kill."

The concept of the Weed Chipper arose through a group of growers discussing weed control in a fallow field when the idea of a rapid response tyne to chip out weeds was conceived.

With investment from the GRDC, a group of agricultural engineers and weeds researchers led by Dr Walsh, along with grower and industry advisors, built and tested prototypes of the Weed Chipper.

The University of Western Australia Agricultural School of Engineering senior lecturer Andrew Guzzomi led the engineering development of the rapid response tyne, which was based on the Shearer Trashworker hydraulic breakout system.

Dr Walsh said the situations where the Weed Chipper is a perfect fit included treating large and/or stressed weeds to prevent seed set and drive down the weed seed bank.

"It's useful as a double knock partner to a herbicide application, particularly if the second spray can't be applied within the ideal timing window," Dr Walsh said.

"It can replace a pre-seeding knockdown with a non-herbicide tool to enable early sowing and provide weed-free conditions to boost crop establishment and competition.

"It's also good for efficient patch management tool to nip herbicide resistance in the bud without compromising moisture and stubble conservation in the fallow."

Extensive field trials were conducted to test the efficacy of the Weed Chipper on a range of winter and summer weeds at varying growth stages and plant sizes.

Dr Walsh said in the 2017 winter and 2017/18 summer growing seasons, the researchers tested four winter and three summer weed species.

They included rigid ryegrass (Lolium rigidum), wild oats (Avena fatua), annual sowthistle (Sonchus oleraceus) and turnip weed (Rapistrum rugosum) and three summer weed species - jungle rice (Echinochloa colona), feather fingergrass (Chloris virgata) and hairy fleabane (Conyza bonariensis) at Narrabri, New South Wales and at Warwick and Gatton in Queensland.

"In the Narrabri field trials the weeds were planted as two-leaf seedlings on eight different occasions so that on the day of treatment the weeds, ranging from two-leaf seedlings to flowering plants, were pitted against the Weed Chipper under the same conditions," Dr Walsh said.

"The result was essentially 100 per cent control of all species, at all growth stages, at all three locations."

In another test, the Weed Chipper was evaluated for weed control efficacy and soil disturbance levels in commercial-scale fallows at three sites, totalling eight hectares, at the University of Sydney's Llara farm at Narrabri.

In this real-world evaluation, it achieved 88pc weed control efficacy with standard v-shaped sweeps.

Across the 8ha trial area, the tynes were triggered 5055 times, equivalent to a weed density of 0.6 plants per 10 square metre.

Being well-suited to the control of larger weeds, this machine provides a fantastic non-chemical option to clean up survivors in a double-knock operation within a conservation cropping system. Photo by AHRI.

Being well-suited to the control of larger weeds, this machine provides a fantastic non-chemical option to clean up survivors in a double-knock operation within a conservation cropping system. Photo by AHRI.

Dr Walsh said the Weed Chipper disturbed only 1.8pc (642m2) of the paddock's surface area during weed control.

"The divot created each time a weed was detected was 0.3m2 and the displaced soil was spread over an area of 2.2m2 in the direction of travel," he said.

"The response tyne is designed so that the amount of soil disturbance can be altered as required to control the target weeds, while the cultivation depth and duration can be increased to target large tap-rooted and fibrous weed species, or reduced for smaller, shallow-rooted species.

"With such low-level disturbance, the Weed Chipper is a practical option for no-till farmers wanting to reduce their reliance on herbicides, particularly glyphosate, in the fallow."

The Weed Chipper concept has been proven to be an effective non-herbicide weed control tool and WA based company Precision Agronomics Australia (PAA) has partnered with UWA to commercialise the novel technology.

It is a non-chemical alternative to optical spraying and the physical upturning of weeds will reduce weed seed-set to potentially prevent or delay resistance evolution.

Field trials showed the tool is a highly-effective way to manage key weed species, even when the plants are up to 70 centimetres in diameter and any tactic that can consistently achieve 90 to 100pc weed control needs to be taken seriously.

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