AN ENGINEER has turned to a microwave oven to help Australian farmers beat the threat posed by chemical-resistant "super" weeds.
Graham Brodie of Melbourne University has adapted microwave technology, mounted on the back of a tractor-pulled trailer, to kills weeds and weed seeds in grain crops as chemical spraying becomes increasingly ineffective, The Australian reports.
After five years of trials, graingrowers deeply worried by the rapid spread of weeds on their farms are excited about the technology's practical potential.
So too are international machinery manufacturers, now beating a path to the gates of Dookie Agricultural College near Benalla to investigate the commercial opportunities offered by the groundbreaking research.
"There was some early limited work using microwaves in the 1970s but the conclusion was it was not a viable because chemicals were so cheap and there were no problems with resistant weeds," Dr Brodie said.
"It's still early days, but what has changed is both that widespread resistance is such a challenge for farming communities and we know definitely from these trials now that microwave kills weeds above the ground and seeds in the soil."
Four microwave panels, each capable of emitting two kilowatts of rays (about double the power of a kitchen microwave oven), are mounted in a row on the back of Dr Brodie's Dookie prototype.
As the tractor moves at walking pace across the paddocks, weeds beneath the directed rays shrivel and die as the intense low frequency microwaves heat and explode the plant cells.
Dr Brodie believes his microwave weed killer will be used both before farmers sow their winter grain crops across entire paddocks, and between close wheat or barley rows once the crops are growing, using precision GPS-controlled technology to protect the crops but kill inter-row weeds.
"Herbicide resistance and environmental concerns already limit the chemical options available for weed management," Dr Brodie said. "In looking for alternative weed treatments, we have found that microwave treatment is immediate, chemical-free and leaves no residue at the treatment site."
Further trials, funded by the Rural Industries Research and Development Corporation, will now determine if the best way to kill more weeds and seeds deep in the soil is to use a more powerful microwave emitter, perhaps five or 10 times as strong as the current model.
A more powerful microwave source might allow the tractor or self-propelled microwave trailer to travel faster across the ground, while still effectively killing weeds.
Dr Brodie predicts his microwave weed killer will be in wide commercial use on Australian farm within six years, providing growers with a safe and chemical-free way to reduce weed competition in their wheat paddocks.
His ultimate goal is to develop a robotic microwave machine or "ground-drone" powered only by solar energy and GPS-guided precision-farming technology, that could be left on its own in a crop or paddock to quietly, efficiently and cheaply control weeds without the need for any human labour.
The only potential downside of the technology is that it can also kill worms and other useful microbes in the soil down to a depth of about 5cm because of the intense microwave "heat" blast generated.
"But we are still working on a lot of those issues; ultimately we might even be able to incorporate weed-seeking (infra-red) technology in it so that the machine only turns its microwave rays on when it encounters a weed," Dr Brodie said.
"Cost-wise we think it will be cheaper or comparable to chemicals, but its main advantage is it kills weeds in such a different way that it gets around the whole problem of chemical resistance."
Weeds have been estimated cost Australian agriculture more than $4 billion each year in control costs and lost production.
Read more on The Australian.