Electric weed control can deliver results comparable to herbicides

The Department of Primary Industries and Regional Development (DPIRD) in Western Australia is leading the project in association with AGXTEND, a brand of CNH Industrial. The Grains Research and Development Corporation, the Cotton Research and Development Corporation, Wine Australia and WA consultants AHA Viticulture are also supporting the project.

Weed control in Australian agricultural systems is becoming increasingly challenging due to the rising prevalence of herbicide resistance. As a result, Australia needs to consider alternative, non-chemical forms of weed management.

Electric weed control machinery

According to a Progress Report, the current electric weed control machinery, as a non-selective weed management strategy, is most likely a good fit for agricultural weed control in non-cropping areas, for urban weed control or in viticulture. Results from field trials showed that electric weed control is highly effective with results comparable to herbicide (glyphosate) treatments.

We saw the best electric weed control after a double application at 2 km/h

DPIRD research scientists Miranda Slaven and Dr Catherine Borger compared the level of control achieved by electro-weeding with herbicide applications, and the results were significant. In August last year, it was clear that – after two passes – electric weed control treatments had a normalised difference vegetation index, or NVDI, value half that of the plots with two applications of glyphosate three weeks after treatment.

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Similar to double application of herbicides

“This trial looked at the effect of electric weed control in non-cropping scenarios”, Ms Slaven says. “We compared the single or double application of electric weed control with a single or double application of herbicides. At the completion of the trial, we saw the best electric weed control after a double application at 2 km h-1. Control was similar to a double application of the herbicides.”

In general, the researchers found that broad leaf weeds are easier to control than grass weeds with electric weed control. But, at the appropriate speeds, grass weed control is excellent with the XPower technology.

A project highlight was the excellent control of wet, fully mature, and exceptionally dense kikuyu at a viticulture site, with wet topsoil due to recent rainfall. This species is difficult to fully control with herbicide.

The damage to plants is immediate

While the manufacturer of the XPower recommends targeting weeds in dry soil, initial results did not indicate that surface soil moisture impacted control. The damage to plants is immediate, making it very easy to visually assess coverage and ensure that areas are not missed.

The influence of soil moisture on the effectiveness of electric weed control on annual ryegrass, kikuyu and wild radish was assessed in a field trial at DPIRD’s Northam Research Facility. Electric weed control effectively reduced the weed population’s density, groundcover and biomass compared to the untreated control.

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Can be effective in wet soil

In this trial and at the viticulture site, topsoil moisture did not have a significant effect on electric weed control efficacy. Therefore, it is likely that electric weed control can be applied after light rainfall, to slightly wet plants, without a reduction in efficiency.

According to Ms Slaven, the high voltage current will take the path of least resistance. “The wetter the soil is, the less resistance there is. In theory, when you apply the electric current to the weeds, if the topsoil is wet, there is potential for electric current to dissipate into the soil, rather than going down into the roots. That can mean that you don’t achieve effective control of the root system, and there is potential for regrowth of the weeds to occur.”

XPower will have an immediate value for winter and spring weed control

“In this initial trial at Northam, we simulated 2mm to 3mm rainfall events before the electric weed control application. We did not find any difference in the effectiveness when the electro-weeding was applied with dry or wet soil. We will continue to look into these effects this year as well and determine if different rainfall events and soil types effect these results.”

The researchers expect that the XPower will have an immediate value for winter and spring weed control in the viticulture and horticulture industries.

Controlling mature annual ryegrass

The scientists also looked at the performance of the machine at various application speeds and growth stages of annual ryegrass. “We wanted to see if we could do an application strategy that is similar to crop-topping or weed wiping, which hasn’t previously been done with this machinery”, Ms Slaven points out.

“Hopefully this will offer an alternative to reduce the weed seed set. These results are still being analysed.” So far, the researchers have found that electric weed control at 1.4 km h-1, controlled mature annual ryegrass, with full senescence occurring 2 to 3 weeks after treatment.

A cereal disease trial at the Muresk Institute in the Wheatbelt region of WA explored whether electric weed control can assist in the management of the Rhizoctonia fungus when annual ryegrass is treated.

Ms Slaven explains that Rhizoctonia is a widespread root disease that results in a yield loss of 1% to 5% in WA cereal crops each year. “We identified a paddock for the trial that was infected with the fungus, and then applied electric weed control to see if it could be used as part of an integrated pest management strategy. So, not only controlling the weed population, but also that of the disease.”

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Soil health

“Because the disease is attached to the root system, there is potential for the electric current to travel down to the roots, and also impact the disease. Our results did not find that there was any reduction in the fungus, but we did find effective control of the annual ryegrass population. And the lack of effect on the Rhizoctonia indicates that there is unlikely to be an impact of electric weed control on the soil microbial population. That is a good outcome as well, particularly for organic growers.”

With any kind of agricultural machinery technology, there may be a fire risk

Current international research has found that use of the XPower machine does not affect soil health, Ms Slaven says. “We have begun to investigate these potential effects using Rhizoctonia as an indicator species and we haven’t found any effect. But we’ll continue to analyse that in viticulture trials where we are more thoroughly analysing the soil bacterial populations. This analysis is outsourced and we are waiting on the results.”

The researchers will also look at potential fire risks, but so far, the risks seem limited. Ms Slaven emphasises that farmers should always be careful. “With any kind of agricultural machinery technology, there may be a fire risk, depending on how you’re operating the machinery and the conditions of the day.”

The researchers hope to find possibilities that might be beneficial for the future development of the technology.

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