Microwaves: More bing for your weed control buck?

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An Australian AgTech startup has secured a significant seed investment to commercialise technology that could revolutionise the agriculture industry and wipe out the need to use chemicals to control weeds.

The Gr owave technology invented by researchers at the University of Melbourne, harnesses the power of microwaves to kill weeds from the inside and rids soil of emergent weeds, dormant seeds as well as reduces pathogens and their impact.

“With the economics of the solution so compelling, the technology has the potential to have an impact on a broad range of agricultural markets,” said Paul Barrett, Growave Director and head of physical sciences at IP Group.

The seed investment came from IP Group, Grain Innovate and Artesian and will be used to take the novel, chemical-free weed treatment to a global market.

“This r epresents the fifth investment by IP Group in Australia and New Zealand with its partnership agreement with the Group of Eight and University of Auckland,” said Paul.

Field trials

“While there is strong international interest in the technology, Growave will firstly focus on domestic markets with new trials commencing on farmland at Dookie in Victoria and in southern Queensland in the Lockyer Valley on an organic vegetable farm.

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“It is anticipated in 18 months the Growave technology will be ready for commercial deployment,” says Paul.

“Herbicide resistance is a growing problem worldwide so people are looking for alternative ways to manage weeds.”

The modular design of the technology means Growave can be integrated into existing farming operations.

“This not only means reducing or eliminating the need for herbicides, but also saving labour associated with weed management,” said Dr Graham Brodie from the University of Melbourne.

“It can be mounted onto a tractor or trailer, and used in wet or windy weather, unlike herbicides and soil fumigation.

“As no chemicals are used, treated crops and fields do not require isolation. It is environmentally friendly and less expensive per hectare than most alternatives,” said Graham.

IP Group is a leading intellectual property commercialisation company focused on evolving great ideas from its partner universities into world-changing businesses. In Australia and New Zealand, IP Group works in close partnership with the Go8 Universities and the University of Auckland to identify ground breaking technologies, rooted in hard science, which have the most promising commercial potential. Artesian is a leading global alternative investment management company with offices in Sydney, Melbourne, Singapore, Shanghai, New York and London. GrainInnovate was established by the Grains Research & Development Corporation (GRDC) and Artesian to deliver innovation for the Australian grains Industry.

SOME BACKGROUND TO MICROWAVES AND WEEDS

Weed seeds

• As early as the 1970s researchers have been studying the lethal effect of microwave heating on seeds, including weed seeds. • This early research showed that weed seed damage was mostly influenced by a combination of seed moisture content and the energy absorbed per seed. In addition, both the specific mass and specific volume of the microwaved seeds were strongly related to seed mortality. • Larger and more rounded seeds focus more energy into their core, which results in higher temperatures at the centre of the seed leading to higher mortality rates. • Subsequent research on wild oats has demonstrated that the weed seed’s susceptibility to microwave treatment is entirely dependent on the surrounding soil temperature. • In the case of wild oats, when the soil temperature rose to 75°C due to microwave treatment, there was a sharp decline in both oat seed and naturalised weed seed germination. • When the soil temperature rose above 80°C, seed germination in all weed species was totally inhibited.

Already emerged weeds

• Back in the 1970s, researchers also considered the effect of microwave energy on growing weed plants – bean (Phaseolus vulgaris) and Honey Mesquite (Prosopis glandulosa) seedlings. • It was discovered that plant aging had little effect on the susceptibility of bean plants to microwave damage, but honey mesquite’s resistance to microwave damage increased with aging. • They also discovered that bean plants were more susceptible to microwave treatment than honey mesquite plants.

In the mid 2000s, the ef fect of microwave treatment on marshmallow (Malva parviflora) seedlings was tested, using a prototype microwave system based on a modified microwave oven.

Based on energy calculations for plants and seeds on the surface of sandy soil, the energy needed to kill dry seeds is an order of magnitude higher than the energy needed to kill already emerged plants.

Costs and benefits?

• In a 2016 field experiment at the University of Melbourne Dookie campus (Victoria), researchers looked at the economic impacts of microwave soil irradiation on farm profitability. • The researchers estimated that the direct and indirect (ie loss of crop yield) costs of chemical weed management is around $150 to $200 per hectare averaged across

Australia’s cropping regions. • In their Dookie field experiment, the researchers estimated that pre-sowing soil irradiation using microwave to kill dry weed seeds had a direct per hectare cost of $400 to $500. But there was a wheat yield increase of almost 40 per cent compared to the ‘control‘ (ie non-microwaved plots). This gave a profit of around $450 per hectare on the pre-sowing microwaved area. • There were also additional benefits of the microwave treatment in terms of better soil nutrient availability and its long-lasting effect (up to three cropping seasons). • The researchers concluded that, in general,

Australian dryland wheat farmers could potentailly realize an additional $370 per hectare using microwave treatment for weed management.

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