Could robot weedkillers replace the need for pesticides?

On a sweltering summer day in central Kansas, farm fields shimmer in the heat as Clint Brauer watches a team of bright yellow robots churn up and down the rows, tirelessly slicing away any weeds that stand in their way while avoiding the growing crops.

The battery-powered machines, 4ft (1.2 metres) long and 2ft (0.6 metres) wide, pick their way through the fields with precision, without any human hand to guide them.

Brauer, a former California-based tech executive who moved back to his family farm in central Kansas after his father developed Parkinson’s disease, sees the robots as critical tools to help farmers reduce their reliance on chemicals and be more protective of their health and the environment.

His Greenfield agricultural technology company now builds and programs its robots in a shed behind an old farmhouse where his grandmother once lived. Twenty farmers are signed up for the robotic services this season, and the company hopes to weed 5,000 acres (2,023 hectares) this year.

“The answer is here,” he said. “This solves a lot of problems for farmers.”

Farmers have been fighting weeds in their fields – pulling, cutting and killing them off with an array of tools – for centuries. Weeds compete with crops for soil moisture and nutrients and can block out sunlight needed for crop growth, cutting into final yields. Over the last 50-plus years, chemical eradication has been the method of choice. It is common for farmers to spray or otherwise apply several weedkilling chemicals on to their fields in a single season.

But as chemical use has expanded, so has scientific evidence that exposure to the toxic substances in weedkillers can cause disease. In addition to glyphosate’s link to cancer, the weedkilling chemical paraquat has been linked to Parkinson’s disease. Another common farm herbicide, atrazine, can be harmful to reproductive health and is linked to several other health problems.

Weedkilling chemicals have also been found to be harmful to the environment, with negative impacts on soil health and on pollinators and other important species. The widespread use of herbicides in farming has fueled weed resistance, leaving many farmers struggling to control weeds in their fields even with repeated applications of herbicides.

A ‘personal mission’

Financial backing is flowing to companies making weedkilling robots from venture capital funds, private investors and large food and agricultural companies eager to make bets on the bots as a means to promote more sustainable food production.

The investment arm of Chipotle Mexican Grill, the global restaurant chain, is among Greenfield’s investors. Christian Gammill, who leads Chipotle’s venture fund, said Greenfield’s work was “important and impactful”. Greenfield has raised about $12m in capital, and is seeking more, according to Brauer.

North Dakota-based Aigen Robotics has raised $19m to date. Its compact robots are powered by solar panels fixed to the top of each machine and are designed to work autonomously, sleeping and waking up on farm fields.

Kenny Lee, the Aigen co-founder and CEO who previously worked in cyber security, said he and partner Richard Wurden, who worked in the electric vehicle industry, are on a “personal mission” to reduce herbicide use in farming. Lee is a survivor of non-Hodgkin lymphoma, a disease the International Agency for Research on Cancer has found can be caused by glyphosate-based weedkillers, such as the popular Roundup brand.

The company and is deploying 50 robots this summer in sugar beet fields in the US Midwest, aiming to grow its fleet to 500 for use with an expanded array of crops.

Other companies are rolling out farm robots designed specifically to spray herbicides in ways that are more precise than conventional methods, according to developers.

Even the global agrochemical company Bayer, which sells Roundup herbicides, is taking an interest in robots for farms.

What skeptics are saying

Still, many farmers and academic experts are skeptical that farm robots can make a substantial difference. They say that there is simply too much farmland and too many diverse needs to be addressed by robots that are costly to make and use. The better path, many say, is for farmers to work with nature, rather than against it.

The model of regenerative agriculture – using a variety of strategies focused on improving soil health, including limiting pesticides, rotating crops, planting crops that provide ground cover to suppress weeds and avoiding disturbing the soil – is the better path, they say.

“I think the robots can be a useful tool as part of an integrated weed approach, but using as a single tool … is probably not going to work that well,” said Adam Davis, a professor and head of the University of Illinois department of crop science.

Wisconsin farmer Ryan Erisman agreed. “The robot weeders represent another round in the arms race against nature,” he said. “So many of our agricultural tools are really weapons … that we use against perceived threats. When we keep running into the same problem year after year or season after season, it’s not our tools, our techniques, or our technology that needs reworking. It is our failure to understand the system we are working in and our relationship to it.”

Despite the naysayers, Kansas farmer Torrey Ball is eagerly awaiting his turn for Greenfield’s robotic fleet. Last year, the company’s robots weeded his sunflower fields. This month they will weed some of his soybean acreage.

Ball is a longtime user of many of the leading weedkilling herbicides and knows first-hand how expensive and how ineffective some products have become as weeds have developed resistance to the widely used chemicals, particularly glyphosate. He also knows of the research showing the risks to human health, and he worries what the chemicals are doing to water quality.

He only runs the robots on a small portion of his 2,000-acre (809-hectare) farm for now, but hopes one day they may help him break free of chemical dependency on all his land.

“If we can use less chemicals I’m all for that,” Ball said. “We’re going to try and leave the ground in better shape than what it was when we took it over, which is hopefully everybody’s goal.”