Automated Weeders Have Arrived in Vegetable Fields
The vegetable production areas of the Central Coast of California have lifted vegetable cultivation to a high art. Except for a 4-inch wide band around the seedline, growers cultivate the entire bed.
That uncultivated band is the area where growers hand weed what survives preemergent herbicides or cultural practices.
For the rest of the bed? Automated weeders remove weeds from the seedline. This technology has mostly thrived in Europe, where low labor availability and high costs reign.
U.S. vegetable growers, now facing similar issues, are adopting automation — including weeders — to supplement increasingly hard-to-find labor. That’s especially true for the last two to three years in the Salinas Valley.
What’s on the Market Today
Currently automated weeders available include:
- Robovator, developed in Denmark by Poulsen Engineering and distributed by Pacific Ag Rentals (Salinas)
- Steketee IC, developed in the Netherlands and distributed by Sutton Ag (Salinas)
- Garford, developed in England and distributed by Quinn Tractor (Salinas).
How Auto Weeding Works
The Robovator and Steketee machines use a split blade that comes together between crop plants to take out weeds and opens as it passes the crop plants (keeper plants).
The Garford machine uses a spinning blade with a notch (see photo); it places the keeper plant in the notch and spins around it to avoid damage.
All these machines use a camera to detect the crop, a computer to make decisions on which plants to keep/remove, and then activate a kill mechanism.
They were designed for use on transplants, which simplifies distinguishing the crop from weeds because the computer only needs to count the pixels of the plants. Transplanted crop plants will initially be larger than weed seedlings, and the computer uses this info to decide which plants to keep and which to eliminate.
A buffer area is left around the keeper plants to avoid cutting roots and causing crop injury. However, weeds can survive in the buffer area. Our team observed automated weeders removed about 51% of the weeds in the seedline and reduced subsequent hand weeding time by 37%. With experience, operators can probably make improvements on these estimates.
What Technology to Watch for
Innovations in auto weeders are continuing. There are a number of concepts being pursued, such as:
Herbicide sprays. An alternative approach killing weeds with a blade in the seedline is a spray mechanism. This concept is being developed by Blue River Technology (Mountain View, CA, now part of John Deere Corp.).
Their Seek & Spray machine uses a sprayer akin to a dot matrix applicator that allows for pinpoint spraying of the seedline around keeper plants. Cotton growers are currently using this method. Glyphosate-resistant weeds are a serious threat to cotton production.
The hope is the Seek & Spray machine will eventually work for vegetable crops. But vegetable production fields present specific challenges, like a greater diversity of crop types and weed species. That may require greater development cost to program the machine to work effectively.
Imaging to recognize weeds. It’s an exciting time for weed detection technology. A rapidly developing field, weed technology advances include deep learning, where engineers train the computer to recognize weeds by feeding it weed images. The goal is for the weeder to distinguish weeds from crop. One major challenge is this technology must be effective at speeds of 3-5 miles per hour.
Truly autonomous machines. Watch for modules that will cultivate a field autonomously. Some of these machines just cultivate (Naio, France; AgBot, Australia; Anatis, France), while others are being developed to cultivate as well as remove weeds from the seedline (FarmWise, San Francisco, CA). One interesting concept is a solar powered autonomous weeder, EcoRobotix (Switzerland) that removes weeds from the seedline by applying a micro-dose of herbicide.
How Well Do Current Autoweeders Perform?
Current commercial growers using auto weeding provides a useful measure of weed control in lettuce production.
As mentioned, they do not remove all weeds, and workers must follow up with hand weeding to get weed control to acceptable levels. That said, the subsequent hand weeding operations are quicker and cheaper than fields where the auto weeder was used.
Low to moderate weed populations are necessary to help the machines work effectively. The machines cannot fix a big weedy mess which underscores the point that good weed control practices that keep weed populations at low to moderate levels, as well as a good preemergent herbicide program is still as important, if not more so, for the use of autoweeders to function effectively.
At present, the automated weeders available in the Salinas Valley are quite expensive and only affordable by larger operations. However, we are still at the beginning stages of the adoption of this technology.
One company is offering monthly rentals of their machine, which does two things:
- It allows a grower to try this technology out before making a large investment.
- It allows smaller growers access to the machine.
It’ll be fascinating to watch this technology’s adoption and development as time moves forward. From where I sit, it appears that automated weeding will continue to gain traction in the farming community, and many companies are certainly interested in developing this type of technology for growers.