Electro Weeding Sparks Interest

electric weed control
Units like the XPower XPS zap weeds with an electric current, delivered via charged metal combs sweeping over the ground.

As weeds become increasingly resistant to chemical herbicides, pressure is mounting to find alternative methods for weed control throughout Australia. JOHN POWER investigates the use of electric current to tackle weeds.

OPERATOR: Department of Primary Industries & Regional Development, WA
LOCATION: Southwest Western Australia
CONTACT: www.wa.gov.au

Herbicides are losing their effectiveness across the world in the never-ending battle against weeds, prompting renewed interest in alternative methods to eradicate or suppress pest plants. 

Just as importantly, there is a widespread philosophical desire to minimise the use of potentially toxic chemicals in sensitive environments, and to ‘find another way’ to control weeds.

The use of electric current to kill plants, or ‘electro weeding’, has been acknowledged for over a century, but modern technologies that are both affordable and (hopefully) effective are only now emerging as viable alternatives to chemical herbicides. These technologies, the majority of which are marketed as tractor-mounted systems for commercial use, are finding boutique markets around the world.

In Australia, university research into electro weeding (and variants on the theme) has been underway for years –and now the first research-based trial by a government department is about to commence in Western Australia.

The WA Department of Primary Industries and Regional Development (DPIRD) is awaiting delivery of Zasso tractor-mounted electro weeding machinery from Switzerland in order to conduct a two-year field trial in the state’s Grainbelt region. Units are designed to sweep over weed-infested ground and, upon contact with plants, zap them with an electric current; the charge is meant to kill or severely harm the plant.

In February this year, the DPIRD announced that it will join with Case New Holland Industrial (CNHi) to test the technology’s suitability to control weeds in Australian dryland and irrigated agriculture, in southwest WA. CNHi became a minority shareholder of Zasso back in October 2020, at which time the company also renewed a supply agreement for the XPower Products through the AGXTEND business of CNHi.

The trials will examine which weeds are easiest to control with electricity and the technology’s potential uses in Australian agriculture to generate cost savings and influence crop yields.

Speaking to a Grains Research Updates 2022 virtual forum in February, DPIRD research scientist Miranda Slaven explained that electric weed control could be part of an integrated solution to reduce dependence on chemical inputs and create more sustainable farming systems.

“Finding alternative weed control strategies to chemical measures is important in Australia, due to increasing rates of herbicide resistance and increasingly discerning market demands,” she said.

“This new equipment is at the frontier of agricultural technology, and it is valuable to test it under Australian growing conditions to examine its potential application as a non-chemical methodology in our agronomic systems.”

The equipment will initially be tested on its ability to control weeds on Viticulture and horticulture properties, and later along roadsides and fencelines, as well as its use for fallow weed control at the department’s research facilities in the Grainbelt.

The research will target herbicide-resistant weeds such as annual ryegrass and wild radish, and problematic agricultural weeds, including feathertop Rhodes grass and fleabane, as well as perennial weeds, including kikuyu and wireweed.

The project has support from the Grains Research and Development Corporation; Wine Australia, WA; consultants AHA Viticulture; and the Cotton Research and Development Corporation.

EQUIPMENT USED

Peter Thompson, AGXTEND Product Manager, says the electro weeding equipment being trialled in Australia includes XPower units for Urban application (the XPU) and the XPower for Viticulture (the XPS). The XPU, Peter explains, is targeted at urban environments such as council roadsides, bike tracks, etc, while the XPS is built to manage under-vine weeds in Viticulture. The XPS features a laterally pivoting applicator head that swings back upon contact with the base of the trunk or stem. There is also a configuration (the XPO) for under-tree weed management in orchards, though XPO units will not feature in the Australian trial. “We haven’t brought in the XPO at this point in the trial, but initially Viticulture, Orchards and the Urban/Councils would be the focus markets to begin,” Peter says.

“There are two models available when it comes to the actual power supplies. The 24kW, typically used for the Viticulture and Orchards, and 36kW typically used on the Urban applicator. Both are mounted on the rear 3-point linkage and driven via PTO of the tractor. We recommend a minimum of 110hp to operate the 36kW unit.”

HOW IT WORKS

The concept of the XPower is to create an electrical circuit through the plant, from the biomass above the ground through the roots and back. It is recommended for best results to operate with low top-soil moisture and a medium-to-high subsoil moisture level. As water is conductive, a high level of moisture on the surface will result in the voltage passing back the other electrodes above the root system, limiting the effect to the root system of the plant.

The physical characteristics of different kinds of weeds, unsurprisingly, will influence the behaviour of the electro weeding treatment.

“Much like chemical application, there are limitations and/or different approaches taken depending on the weed type,” Peter says. “A broad leaf weed will have a larger surface area, thus conducting more voltage through the plant versus a grass-like weed. The root system will also be a factor; a dense root system means voltage is going to be distributed over a greater area compared to a tap root-type weed, where voltage is concentrated down to the central point.”

Like any method of weed control, conditions such as plant maturity and density will also affect the management approach. For a ‘woody’ weed, the best approach would be to remove as much of the biomass of the weed as possible above-ground initially, and then treat the young regrowth with the XPower unit. 

“By doing this, the mature part of the weed, which has high lignin content, is removed – the higher the lignin content, the less conductive the weed becomes,” Peter says. “It also removes a lot of the biomass above the ground, allowing the voltage to conduct through the new growth of the weed down into the root system, creating more effective results.”

EFFECTS ON SOIL

An important aspect of the trial will be the effect of electro weeding on soil. Trial project lead, research scientist Catherine Borger, says a literature review and reports from Europe suggest soil health and soil biota are not compromised by the technology.

“Our research will include an analysis of the technology’s effect on soil health, including soil microbial density and diversity, as well as soil root pathogens, such as rhizoctonia,” Catherine says.

Meantime, Peter adds that “Studies to date show no harm to the soil environment or other roots.”

FIRE RISKS

Another vital feature of the research will be testing to ascertain the potential for the equipment to cause fires.

“Due to the high voltage used there is the likelihood of arcing to occur,” Peter admits. “Because of this, it is recommended not to operate in environments with possible hazards such as built-up residue/fuel in dry conditions. If planning to adopt XPower weed control, other management practices need to be taken into consideration to manage these risks. However, the risk in the Urban environment and Viticulture settings targeting winter weeds is low.”

The XPower XPS electro weeding unit is designed for applications in Viticulture.

MAINTENANCE & COSTS

Very little maintenance is required to maintain the equipment. Electrodes are typically replaced annually on the XPS, and up to three times a year on the XPU, given that it tends to work on more abrasive surfaces. “It’s a very simple process to change the actual electrodes,” Peter explains. “For safety, it is recommended the units be inspected annually by a qualified technician.”

Prices differ depending on the applicator and size of the Power Supply unit. Currently, a typical XPS setup is approximately 110,000€ (AUD $165,000) and the XPU 135,000€ (AUD $200,000).