April 2023
By Eric Buchanan, Renewable Energy Scientist
Minnesota farmers and land managers are engaged in an annual battle to control weeds. Each year, significant amounts of herbicide, diesel fuel, labor, and money are expended to stay ahead of weeds. Control of weeds is critical in the production of food. The current method of using herbicides for weed control has been very effective but may have unintentional and harmful consequences to our air, land, water, and wildlife resources. One of these consequences is herbicide drift to adjacent lands with negative impacts on desired native plant species including pollinator habitat. Another is the evolution of herbicide tolerant “super weeds” that are getting more difficult to control. Moreover, the use of fossil fuels in herbicide production and tractor-based weed control is a difficult-to-address portion of agriculture’s carbon footprint. Weeding robots powered by renewable energy provide an opportunity to address these concerns and provide a more robust weed control solution for organic farmers.
Continual pressure to increase crop yields results in more stress on agricultural ecosystems. Robotic weeding can eliminate some of this stress while allowing productivity gains without as many negative side effects. Furthermore, an effective weeding solution for organic crops could lead to more widespread organic adoption reducing the use of synthetic fertilizer which is a large portion of the carbon footprint of corn production.
The Weed Terminator project is a collaboration between researchers at the WCROC and computer scientists from the U of MN’s College of Science and Engineering to develop an autonomous robot to operate in crop fields and remove weeds. Like the Terminator from the movies, this robot will have advanced programming to hunt for its enemy (weeds) and eliminate them. The Weed Terminator will use GPS navigation and onboard cameras to find its way through corn rows and determine where the weeds are.
Several weed control methods were investigated including spot spraying, ground contact methods like tilling, and a few unconventional methods such as lasers and electrocution. After prototyping several concepts something as simple as mowing proved to work best. Mowing has the advantages of requiring little energy to operate and not requiring any additional material like herbicide to be hauled on the robot. Mowing works equally well on flexible weeds like grass and stout weeds like mature burdock, and it is an acceptable method for organic fields.
A robotic vehicle was purchased from a company in Norway. A carbon fiber frame was designed and built at the WCROC to configure the robot to span two corn rows while providing enough clearance for mature corn plants and to support mowing implements near ground level. Mowing implements are being designed to eliminate weeds right up to the corn stalks.
The Weed Terminator will be powered by solar energy using the same solar charging trailer that was developed for the Cowbot project – an earlier robot designed to mow weeds in cow pastures.
Tractors and traditional implements are made as large as possible to increase the productivity of one driver. If a tractor/implement doesn’t need a driver, however, different solutions are possible. Weeding with smaller vehicles – even one row at a time – allows for more comprehensive weeding and 30 single row robots can work just as well as, or maybe even better than, a single 30 row implement and may even cover more ground since they can work around the clock.
The Weed Terminator project is part of our goal to reduce fossil fuel use in agriculture through strategic farm electrification. The Weed Terminator will be tested in WCROC fields this summer and demonstrated at Farmfest in August. Just like in the Terminator movies, the future may appear in the present faster than you think!