Laser targeting

A team of scientists at Leibniz University and a laser center in Hanover are developing an alternative to herbicides that would use robots or flying drones to zap weeds with laser beams.

Chickweed, dandelion and shepherd's purse are typical pests that have beleaguered farmers in central Europe since the arrival of agriculture. Today these weeds compete with sprouting corn, rapeseed or turnips for sunlight, water and soil nutrients.

Until now, conventional farms have battled these pests with expensive herbicides that are often poisonous and can spread to land and water beyond the target plant.

"Our goal is to develop a more environmentally-friendly way of getting rid of weeds. The use of herbicides is associated with risks", said Christian Marx, a researcher with the Laser Zentrum Hannover.

The laser weed control project is headed by Thomas Rath and Heinz Haferkamp at the Leibniz University Hanover.

Less labor

In Germany, some 16 million liters of herbicides are used every year, he said.

In organic farming, the weeds are yanked out by hand or scorched away. Although this is more environmentally friendly than herbicides, it is labor intensive and not practical for large-scale conventional agriculture.

The main challenge for the laser project, which is being supported by the German Research Foundation, is to develop sensors that could distinguish the correct species of plant and be able to direct the laser at just the right point.

"It would be no good if it would kill anything green," Marx said.

The beams focus their potency on the weed's growth center, killing it. They also have to be just the right intensity to kill the plant. Previous research suggests beams that are too weak actually promote plant growth.

"A field doesn't need to be perfectly free from weeds. It's important to give crops an advantage of two to four weeks and kill unwanted weeds in that period," Marx said. "After that crops like sugar beet have branched out enough to suppress the weeds on its own."

Various applications

The robots or drones have cameras that record accurate images of the crops, which are then processed by special software that recognizes the plant and optimally positions the laser beam.

The agricultural industry has shown interest in the project, which is currently being tested in a greenhouse.

"A laser works only where it's supposed to. Compare it to destroying weeds with a gas burner: This technique heats up its environment and is difficult to handle when there's wind. A laser works on point," Marx said.

The researchers think the laser tool is best suited for use in greenhouses or tree nurseries.

Large fields would present a challenge for the laser robots, which could not be mounted on a tractor since the shaking motion would prevent accuracy.

Another possibility is drones, or small robotic planes that would fly over the fields. These could also fight weeds near protected waters, where herbicides are not allowed to be used. According to Marx, the German railway service has expressed interest in the project as well.

"30 percent of the railway tracks are in water protection areas where you can't use herbicides anyway."

The researchers are planning further trials outdoors but say it will take at least five more years before the laser is ready to market.

Author: Andreas Sten-Ziemons / Sarah Steffen / sad
Editor: Nathan Witkop