In this day and age of self-driving cars, prescription seeding via satellite guidance, and variable-rate nitrogen application based on plant color, it was probably only a matter of time before artificial intelligence took on a role in weed control. If there’s any doubt about the future of robotic weeders, consider that John Deere recently saw fit to spend $305 million to acquire Blue River Technology (BRT), a California company that created Lettuce Bot.

Using a built-in camera, the Lettuce Bot scans the field using algorithms and machine vision to identify each sprout as lettuce or a weed image in as little as .02 seconds and sprays the unwanted plant with a targeted jet of herbicide.

Building on that, the company next introduced its See & Spray technology. Relying on a massive library of plant and weed images, the machine has the unique ability to distinguish the slightest differences between the crop and weeds and target the latter with the help of robotic nozzles that are both accurate and precise.

However, Willy Pell, director of new technology at BRT, stops short of calling the technology artificial intelligence. Instead, he says it’s closer to “really good memorization.”

While it’s too early to know how John Deere will incorporate the technology into other machines, it does plan to keep the 60-person company at its present location in Sunnyvale, California. It also plans to continue cotton and soybean field-testing in 2018.

In the meantime, Pell says the existing machine can be taught to make other types of applications, explaining that, “You can flip the technology if you want to apply fungicide or fertilizer on the crop.”

Since the See & Spray technology applies a microjet of herbicide to the weeds only (as opposed to a broadcast application across the whole field), the machine is said to reduce chemical use by about 90%.

unmanned machines

Using much the same technology as the See & Spray machine, a company in Switzerland hopes to make the weeding process autonomous. Using a built-in camera, GPS guidance, and a series of sensors, the solar-powered robot from ecoRobotix Ltd. is designed to follow crop rows and to detect the presence of weeds in and between the rows. Two robotic arms then target each individual weed with a microdose of herbicide.

“Because it adapts its speed to the concentration of weeds, it is most suitable for use in fields where the level of concentration is low to moderate, in order to cover the ground at a reasonable speed,” explains Claude Juriens, business development manager for ecoRobotix.

Unfortunately, Juriens says it will be at least another year before the company is ready to look at markets outside of Europe. Even within his own country, he doesn’t see the robotic weeder being available for sale before the end of 2018.

According to the specifications, the average speed of the machine is close to 78 feet per minute, and it has a working width of around 6½ feet (2 meters).

incorporating mechanical tools

Spot treatment with chemicals isn’t the only option in the world of robotic weeders, though. At least two companies are already marketing robotic machines that incorporate mechanical tools. As an example, F. Poulsen Engineering, based in Denmark, offers the Robovator, which is a vision-based hoeing machine for controlling weeds in row crops.

Equipped with a special plant-detection camera above each row, this machine not only tills the soil between the rows but also hoes between each plant in the row using a mechanical tool operated by hydraulic power. The company also offers a thermal weeding model that uses pinpoint flames to eradicate weeds.

“The software for the Robovator was originally designed for transplanted lettuce,” says Frank Poulsen, founder of F. Poulsen Engineering. “Now we are working on seeded crops, as well. We see no reason why it cannot be used on closely spaced crops, as the mechanical machine can work on crops spaced 4 inches apart, while the thermal version can go down to 2 inches. Consequently, the Robovator can already be used on a number of crops, and our customers still find new ways to use the machine.”

According to Bartley Walker with Pacific Ag Rentals (PAR) in Salinas, California, the Robovator can remove from 95% to 98% of the weeds in transplanted crops and 85% to 90% in seeded crops. As the only dealer for Robovator in the U.S., Walker says PAR not only sells the machine but also offers rentals and custom weeding services in which it provides the tractor, machine, and operator.

“The Robovator can easily be adjusted to any row spacing from 9 to 30 inches and is available in three- to six-row designs for any bed width up to 90 inches,” he says. “While most of the machines are still used on vegetables, we’re continually finding new applications for them. Most recently, we’ve used them to weed watermelons and potatoes. In fact, they’ve already been used on more than 20,000 acres since we brought them to the U.S. The only restriction is the machine won’t work on crops with a closed canopy.”

Walker notes that while the price obviously depends on bar length, number of rows, accessories, and so on to match the application, the current unit ranges from $125,000 to $160,000, including around $15,000 worth of modifications that PAR makes to the machine to beef it up for the U.S. market.

“Still, some customers have seen a return on investment in as little as six months in labor-intensive crops,” he adds. “In essence, one Robovator can replace 10 laborers.”

Robovator

Steketee IC WEEDER

A similar machine from a company based in the Netherlands is the Steketee IC Weeder. Like the Robovator, it, too, uses camera images to calculate the position of plants and then hoes around them.

Joe Sutton, COO of Sutton Ag Enterprises in Salinas, California, says the dealership has already sold around a half-dozen Steketee IC Weeders since becoming the sole U.S. distributor in 2015. However, nearly all of them, to date, have gone to lettuce farms.

“It’s mainly used in high-value row-crop vegetables that have previously been very labor-intensive due, in part, to the price and working speed,” Sutton relates.

He says a machine that covers an 80-inch bed, or about five rows of lettuce, costs in the range of $100,000. A three-bed version sells at around $230,000.

Meanwhile, the operating speed for both the Robovator and Steketee machine is generally around 3 mph. Although Poulsen says the limiting factor with the Robovator is not how fast the machine can operate, but the type of crop and its sensibility to dirt on the leaves.

“Lettuce growers,” he explains, “prefer the leaves to be clean. Other crops are much more tolerant and allow for a speed of 4 mph.”

That doesn’t mean such machines won’t someday be found in North America’s row-crop fields, though.

alternatives needed

By some estimates, 255 different weed species have already developed resistance in 92 crops in 70 countries. Yet, no major new herbicide mode of action has been introduced to the marketplace for almost 20 years. This leaves the door wide open for autonomous robotic weeders, as well as manned robotic-weeding implements.

Combined, they represent an emerging industry that’s predicted to be worth $400 million by 2025. It’s no wonder John Deere has taken notice and invested in the technology.