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Farming with Robots

Can more mechanization reduce the use of chemical herbicides?

Weeds, farmers’ biggest headache since time immemorial, just won’t stop popping up.

Modern agricultural technology thought it had weeds beaten with its synthetic pesticides and gene manipulation. But nature has come roaring back with evolved weeds robust enough to resist the chemicals farmers typically throw at them. And so they throw more. But herbicide overuse threatens the health of insect and animal life, and maybe ours, too. Last month an agency of the World Health Organization declared glyphosate – the active ingredient in Monsanto’s Roundup – a possible human carcinogen.

But technology may yet come to the rescue. Teams of engineers around the world are hard at work inventing cutting-edge, weed-busting robots to step in and take over from broadcast herbicides. These robots just might make good on biotechnology’s broken promise: reducing the amount of chemicals used to grow our food.

photo of a solar panel-covered device on wheels in a farm fieldphoto courtesy the Australian Centre for Field RoboticsThe Ladybird, an autonomous weed-killer.

Technology has made it possible for just 2 percent of the US population to feed the rest of the nation. Biotechnology’s herbicide-tolerant crops made weed suppression easier with blanket spraying. Today, the vast majority of soybean, corn and cotton fields are planted with glyphosate-tolerant varieties.

According to a study by Charles Benbrook, total herbicide use in the United States increased by 527 million pounds between 1996 and 2011. That opened the door to glyphosate-resistant weeds, which now infest more than 62 million acres of US cropland, threatening farmers’ yields. The farm chemical industry’s solution? They’re promoting new seeds, this time tolerant of the additional and more toxic herbicides 2,4-D and dicamba. The chemical treadmill just keeps going.

Now, it’s a long way from “The Jetsons” to today’s farm robots. Most weeding bots still can’t navigate themselves around a farm field. They depend on a human driver, who brings a common sense approach, something engineers can’t yet program into computers.

But what robots do bring is enough accuracy and precision to potentially reverse escalating herbicide use trends (though they would not necessarily eliminate the use of herbicides). Using sophisticated computer vision technology, robots can distinguish weeds and either uproot or shoot them with tiny spot sprays of a deadly liquid. Even if that liquid is a conventional herbicide, a switch from today’s blanket spraying to spot spraying could reduce herbicide use by an estimated 90 percent, the manufacturers claim.  

Because spot spraying uses small amounts of herbicide, robotic weeding vehicles can be relatively light and nimble. Ladybird, a driverless research robot developed by the Australian Centre for Field Robotics at the University of Sydney, can trundle up and down field rows using only the solar power generated by the panels on its back. “You’ve got an aging population over here on farms, you’ve got a growing middle class in China and India. We’ve got to make more food with less resources,” says Ladybird’s systems engineer Mark Calleija. He sees platoons of driverless weeding bots patrolling Australian farm fields in as little as two or three years’ time.

LettuceBot, by Blue River Technology of Sunnyvale, California, may need a driver, but, unlike Ladybird, it has progressed beyond the research stage. LettuceBot earns its keep by thinning lettuce seedlings on fields in Salinas, California and Arizona. And it does that without herbicides. The machine sends out a spritz of fertilizer instead – fertilizer so concentrated that it scorches and kills the plants it lands on. Once the fertilizer on the dead plants is absorbed back into the earth, it feeds the plants still left standing.

The next step for LettuceBot – once the company sources an organic fertilizer that can kill – is targeting weeds in organic agriculture. “This is the number one reason why organic products cost more than conventional production–the fact they can’t use herbicides to control weeds,” says Blue River CEO Jorge Heraud. Robots might help drive down the cost of organic food, but, in the process, they’ll snatch jobs from farm workers. In lettuce thinning, for instance, a driver and his robot can do the work of up to 25 hand weeders. Which isn’t to say those weeders are easy to find. “You need to have a little army of people,” says Heraud. “There’s a big shortage of labour to do this job.”

LettuceBot has a competitor in Robocrop. This is a line of precision-guided hoes and in-row weeders developed by Garford Farm Machinery, a British company founded – not by engineers – but by a family of farmers. Like LettuceBot, Robocrop’s newest spot-spray product can kill with shots of either herbicide or fertilizer. It’s also used to apply nematodes, beneficial soil microorganisms that control pests. Precisely targeted applications in cabbage have reduced the quantity of nematodes needed by 90 percent. The spot sprayer is also used to shoot organic compost tea at crop leaves to prevent foliage problems.

Digging a plant out by its roots is known as “mechanical” weeding and, if done with as little soil disturbance as possible, it’s one of the most sustainable ways to weed. Garford is a veteran of robotic mechanical weeding, having marketed its first camera-guided hoe back in 2000. Its newest in-row mechanical weeder clears 98 percent of a field’s surface, using rotating tines that reach to within two inches of each crop plant. Five hundred of these manned robots have so far been sold around the world, including in the United States.

Mechanical weeding remains one of few ways to tackle herbicide-resistant weeds. Even the UK – which has no large-scale genetically modified plantings – is plagued with resistant weeds, especially in its wheat fields. That’s because of tough environmental restrictions on some herbicides, leading others to being overused. The weeds may spell trouble for British farmers, but they create an opportunity for Garford Farm Machinery. “We see a future where we could be one of the only options as far as wheat growing is concerned,” says Philip Garford, the company’s managing director.

Herbicide-tolerant biotechnology was sold to American farmers partly on its promise to reduce chemical use on crops. And look what happened. It’s too early to tell if weeding robots will make good on that same promise, but all signs point to it. Because whether robots attack weeds using a surgical drop of herbicide or organic fertilizer, or whether they pull weeds up by their roots, the end result should be the same – a significant decrease in the volume of herbicides that can harm insect populations, pollute waterways, and end up on our plates. It’s still early days in robotic weeding, but it’s easy to see the technology has the potential to be hugely disruptive. Robots could even eliminate the need for herbicide-resistant crops altogether, their inventors claim.

“It’s an inspiring goal, something that I see two or three steps removed from where we are now,” says Heraud. “But we’re going to get there; we’re going to have this large impact.”

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