The Hortibot team is now planning to equip the robot with modular tools for precision spraying and mechanical weed removal. The aim here is to first identify the weeds, and then either spray them individually without hitting the crops or remove them without damaging nearby crops.
“In recent years, there has been an increasing interest in the use of mechanical intra-row weeders because of concern over environmental degradation and a growing demand for organically produced food,” says Athanasios Dedousis, an agricultural engineer who has been developing such a system at Cranfield University, in the United Kingdom.
But getting it all working is likely to be a huge challenge, says Chris Melhuish, director of the Bristol Robotics Laboratory, in the United Kingdom. “To get a machine to do that is extremely difficult,” he says.
Jørgensen agrees. There has been a lot of research using hyperspectral analysis to try to identify unique signatures of different plants based on the frequencies of light they absorb, he says, but it turns out that their absorption depends very much on the nutritional health of the plant.
So Jørgensen’s lab is taking a different approach. “We use shape analysis,” he says. By analyzing the proximity, orientation, and position of leaves relative to each other, it’s possible to distinguish weeds from crop plants. Difficulties arise when the leaves from different plants overlap or obscure each other, but Jørgensen believes it’s an approach that will eventually prove more reliable than spectral analysis.
Similarly, the mechanical removal of plants is far from straightforward, says Dedousis. Crop rows are not always straight, and plants are not equally spaced. And because some areas can have high levels of weed infestation, the mechanisms for removing the weeds need to be accurate down to about 50 millimeters, Dedousis says.
But the significant challenge is likely to come down to economics, says Melhuish. “At the moment, there is no way [the robot] would be cost-effective,” he says. The estimated cost of Hortibot is about $55,000. With migrant workers in both Europe and the United States willing to work for low wages, it’s difficult to see how the robot could compete, he says.
Hortibot’s cost could be offset by its productivity, says Dedousis. Weeding is repetitive work. Robots can do it round-the-clock and in all weather conditions. For organic farmers, this could be a real boon. “Hortibot is the way towards the future,” Dedousis says. But he predicts that it will take some years before it’s ready for commercial farming.
Indeed, Jørgensen says that before the robot can be commercialized, some fundamental redesigns are necessary. These include increasing the wheel gauge to enable Hortibot to cover more rows of crops with each sweep and increasing the clearance to make the robot suitable for a wide range of crops.
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