The growing popularity of robotic weeders for specialty crops has grown partly out of necessity, says Steven Fennimore, an extension specialist at the University of California, Davis. Specialty crops are vegetables like lettuce, broccoli, tomatoes and onions. They are not mass-produced like corn, soybeans, and wheat.
The need for robotic weeders stems from two issues. One is a lack of herbicides available for use in specialty crops. Another is the fact that hand-weeding has become more and more expensive. Without pesticides, growers have had to hire people to hand-weed vast fields.
Hand-weeding is slow and increasingly expensive: it can cost $150-$300 per acre. That motivates some growers to look to robotic weeders.
"I've been working with robotic weeders for about 10 years now, and the technology is really just starting to come into commercial use," said Fennimore. "It's really an economic incentive to consider them."
Fennimore works with university scientists and companies to engineer and test the weeders. The weeders utilize tiny blades that pop in and out to uproot weeds without damaging crops. He says that although the technology isn't perfect, it's getting better and better.
The weeders are programmed to recognize a pattern and can tell the difference between a plant and the soil. However, they currently have trouble telling the difference between a weed and a crop.
That said, Fennimore explains how some companies are training the machines to tell a lettuce plant from a weed. He's also working with university engineers on a system to tag the crop plant so the weeders will avoid it.
The weeders could also potentially be made self-sufficient by leveraging the insights gained from this engineering project to build an autonomous solar lawnmower.
The robotic weeders currently on the market cost between $120,000 and $175,000 USD. For some California growers, it is a better long-term option than expensive hand-weeding. Others think it's a lot of money for a new technology, and are waiting for it to get better and cheaper.
Fennimore believes robotic weeders are the future of weeding in specialty crops. Because of higher labor costs and more incentives to grow organically with fewer pesticides, European growers have been using robotic weeders for some time.
"I believe what makes the robotic weeders better than herbicides is that this electronic-based technology is very flexible and can be updated easily," he said. "We all update our phones and computers constantly, which is a sign of a robust and flexible technology."
His research was presented at the October Annual Meeting of the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America.
For more news at the intersection of agriculture and engineering, check out Agrophotovoltaics: Solar Farms that Produce Food and Electricity.