Australasian Science: Australia's authority on science since 1938

Lasers Slash Herbicide Use

By Stephen Luntz

Weed identification technology could slash herbicide use in farming, saving money and the environment while reducing concerns about potential health effects.

Edith Cowan University’s (ECU) Photonic Weed Detection System scans a field with three lasers, two in the visible light range and one in the infrared. Weeds will reflect back different proportions of the light from each laser than the planted crop, allowing the system to automatically distinguish friend from foe, hitting only the weeds with a stream of targeted herbicide. By preventing the need to spray weed removers across the whole field, the process can cut herbicide use by 75%.

ECU Electron Research Institute Director Prof Kamal Alameh says the system “cannot distinguish everything from everything” so it must be tuned to distinguish the most common weeds from the crop to be protected. Consequently, rarer weeds may escape being sprayed, but by their nature these are a small problem.

“For sugar crops 95% of the weeds are one species,” he says. When protecting cotton, which is threatened by multiple weeds, the system is simply programmed to spray anything with a different light signature from cotton itself.

“We could distinguish more species if we added more lasers, but that would increase the cost and slow the system down as more processing would be required,” Alameh says.

Australian farmers spend almost a billion dollars per year on herbicide, and the amount is rising. Photonic Detection Systems, ECU’s corporate partner, will lease the detection modules to farmers. Alameh estimates that, if mass-produced, each module will cost around $1500, although each unit will only cover a relatively small area in a single pass.

The availability of better targeting techniques could have unexpected effects. Alameh says that if crops are no longer being exposed to herbicide there may be no need for herbicide-resistant varieties. Round-up resistant soy, corn and canola are the most widely used genetically modified crops.

Besides the cost savings, reduced herbicide use will help crops grow better. Moreover, herbicide exposure may be associated with conditions as diverse as Parkinson’s disease, skin rashes and breast cancer.