A machine that kills weeds with laser beams can reduce dependence on chemical solutions, protect crops, eliminate unnecessary tillage and save farmers thousands of rands.
By Amelia Genis, Senior Journalist at African Farming and Landbouweekblad
Since Carbon Robotics, a Seattle-based company, launched the LaserWeeder in February 2022, it has sold about 100 of these machines.
Here’s how the Cornell Chronicle, which publishes news from Cornell University in New York, described the LaserWeeder in an article: It is a large machine that passes over crop rows and take photos. A deep-learning computer program analyses the images to distinguish weeds from crops. Then the lasers zap the weeds to kill them. The program also allows farmers to prioritise types of weeds to target, such as small plants growing close to crops that may be difficult for humans to spot and remove.
The price tag for one of these machine is reportedly up to $1,5 million, although the model is not specified.
Building on the original design and farmer feedback, Carbon Robotics has since launched the LaserWeeder G2 series, which now includes five models. The smallest can target at least 3 000 plants per minute, whereas the larger models handle significantly more.
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Researchers Compare Laser Technology With Leading Herbicides
The College of Agriculture and Life Sciences at Cornell University recently conducted trials on farms in New Jersey and New York, and found that the laser weeding was as effective as – or even more effective than – three commonly used broadleaf herbicides in controlling annual weeds.
The herbicides used in the trials were S-metolachlor (L11118, Act 36 of 1947), bentazone (L7720, Act 36 of 1947) and phenmedipham (not registered in South Africa). Trials were carried out in beet, spinach and pea fields.
According to the Cornell Chronicle, the LaserWeeders performed well against weeds such as common pigweed (Chenopodium album) and annual ragweed (Ambrosia artemisiifolia), but were less effective on common purslane (Portulaca oleracea) and annual grasses.
The reason for this is that laser beams target a plant’s growing point, or meristem, and some weed species have hidden meristems. For example, grasses’ growing points are underground. The machines were also generally more effective against smaller weeds, which require less energy to destroy.
Compared to untreated controls, laser weeding reduced the percentage of a field covered by weeds by up to 45%; and reduced weed density – the number of weeds present in a square meter – by up to 66%, resulting in 97% less weed biomass by season’s end.
Another advantage was that crop growth was hardly affected – crop stunting was less than 1%. In fact, crop biomass increased by up to 30% when laser weeding replaced herbicide use.
