Guidance Technology for Weeding Tools
Fact Sheet | Guidance Technology for Weeding Tools
TRACTOR GUIDANCE
Tractor guidance ensures a tractor returns to the same spot over time. If planting in May, how close can the guidance bring that tractor to the exact same path, when cultivating in June, or harvesting in October? Tractor guidance improves the accuracy of cultivators and can also alleviate soil compaction by concentrating field traffic in the same areas.
Guidance is achieved through a transponder in the tractor that communicates with a satellite. The system then refines the location by also communicating with an on-farm base station or a cell-tower. This triangulation between three locations ensures precise tractor guidance.
There are two levels of tractor guidance, and they differ in cost, accuracy, and repeatability over time: Auto-Steer and RTK Guidance.
Auto-steer
Auto-steer is guided by the WAAS network, which is run by the FAA. It can bring a tractor within six inches of a track driven 15 minutes earlier. However, with more time between passes, such as from May to June or October, there is more variability. This degree of accuracy may be sufficient for tillage, but not for future cultivation or planting. The best use for the less accurate WAAS tractor guidance system is for tillage, spraying and spreading, where being six inches off is acceptable.
RTK Guidance
RTK guidance is more expensive, but provides greater accuracy, and better repeatability over time. Although RTK is marketed as accurate to within less than an inch, this is often not true given actual conditions in the field. One farmer says, “RTK is only sub-inch accurate on a cement highway. In a field with chunks of soil or elevation changes, that is not true.” RTK guidance is best suited for operations that require higher precision, such as planting, cultivating, harvesting, and strip-tilling. For example, with RTK, farmers can reliably strip-till carrots, because strip-tillage only tills in a narrow strip where the crop is planted. The farmer needs to know that they are planting exactly where they tilled, and RTK gives them the precision to do that.
USING TRACTOR GUIDANCE TO IMPROVE CULTIVATION
RTK can be accurate to within an inch, depending on conditions, and is repeatable months later. Many farmers find that RTK is useful for cultivation by mapping where the tractor drives during planting, and then having the tractor follow that same path when cultivating.
If a farmer is using RTK only to guide their cultivator, the cultivator will be rigidly mounted to the tractor, so that it follows where the tractor drives. This level of accuracy can be good enough if farmers are on flat ground with no sidehills. The limitation though, is that when planting, if the planter hits a stone, jumps, or slides a little down a slope, the tractor doesn’t know that the planter skipped over a few inches. When cultivating later, if the cultivator is guided only by RTK, the implement may kill that inaccurately-planted section.
RTK only knows where the tractor is, but not the crop. The tractor knows only where it has driven, not where the crop row actually is. As a result, when using RTK guidance alone for cultivation, accuracy can be reduced, leading to fewer weeds being eliminated.
TAKE AWAY
RTK-only cultivation can work well on flat land or with larger crops, but the cultivator sweeps will need to be adjusted further away from the row, and using in-row tools like finger weeders will be more challenging.
CAMERA-GUIDANCE ON THE CULTIVATOR
Getting the Most Accurate Weed Control Possible
With RTK guiding the tractor, the farmer is free to focus on other things, like monitoring the cultivator behind the tractor. RTK will position the tractor, and therefore the cultivator, within inches of where it needs to be. However, to get the weeding tools as close to the crop row as possible, pair an RTK-guided tractor with a camera-guided cultivator that “sees” the crop row.
A camera-guided cultivator has a camera mounted on the cultivator that detects the crop row. The camera controls a hitch, onto which the cultivator is mounted, with a hydraulic cylinder that can move about 18 inches to the left or right behind the tractor. The camera “sees” the row, and adjusts the hydraulic cylinder in the hitch, which shifts the implement frame to keep the cultivator centered exactly on the crop row. Many of these models feature quick-hitches, allowing the cultivator to be uncoupled from the hitch and another implement to be attached to the camera-guided hitch.
Because RTK is guiding the tractor, the operator can focus on the cultivator’s camera monitor in the cab to ensure the camera is centering the machine right on the row. The farmer can make adjustments for factors like shadows, crop color, and sidehills, to keep the cultivator aligned to the row. The farmer can also be watching the cultivator itself to ensure it is working as it should and not harming the crop. Cultivator blight can be a serious issue if the farmer cannot turn around often enough to check what the cultivator is doing. Camera-guidance paired with RTK steering allows the farmer to focus on the cultivator, not on the tractor.
The camera-guidance controls are designed with farmers in mind, they’re straightforward and not overly complicated. The hardest part is setting up the camera and running it for the first time. After that, it’s mostly about making small adjustments. When bought new, a company representative will either visit the farm to help with setup or guide the farmer through it over the phone.
While running the cultivator, small adjustments can be manually made through the in-cab interface to ensure that the implement better follows the row. Note that the screen is small, similar to the one used for monitoring a planter. If operating on a sidehill, the cultivator can be adjusted uphill by a few inches, or if cultivating corn on a windy day, where wind blows the corn leaves and causes the camera to misinterpret the row’s center to be downwind, the farmer can adjust the settings to compensate for that.
For the camera to work well, a decent crop stand is required, as well as not having many weeds that are the same size or bigger than the crop - otherwise the camera can’t see the row. There are other factors that affect the camera performance, such as shadows and the camera being mounted too close to the tractor.
A camera-guided cultivator can help the farmer make money in several ways:
• Faster cultivation - less time for operator and able to
cultivate in tight weather windows
• Running the cultivator longer - it is draining on the eye and
mind to steer a tractor when cultivating
• Increasing crop yields - from improved weed control
• Better harvest - with fewer weeds
• Improving grain quality - by reducing weed seeds
• Land - landlords are more likely to rent to organic farmers
who have “pretty fields”
FAST FINANCIALS
It costs a Michigan farmer $20,000 to add RTK to a tractor. A camera-guided hitch alone can be $30,000. A camera-guided hitch with a 12-row cultivator can be $50,000. A 12-row cultivator running at 6mph (max speed) in 30’’ rows can cover a 20 acre field in about an hour.
WEED CLIPPERS
Other Options Where Technology is Improving Weed Control
Weed Clippers are selective weeding tools designed to run through more mature small grain crops and cut weeds before they go to seed. They work by exploiting the difference in stem stiffness of the grain versus the weed. The grain stem will bend out of the way of the cutter bar, while the weed remains upright and gets cut. Unlike traditional cultivators, weed clippers do not focus on reducing weed competition with the crop. Instead, their primary purpose is to cut weed seed heads, reducing the weed seed bank and improving grain quality.
Weed Clippers can be mounted on the front or rear of the tractor. If on the front, a front-mounted 3-point hitch is needed. There is a wide cutter bar that extends out on either side of the tractor, equipped with reciprocating blades that cut whatever comes in contact with them. Then, a sweep mechanism bends the weeds into the cutter bar where they are clipped.
Since weed clippers are often quite wide, they can cover many acres per hour. However, farmers need to carefully choose the width of the tool, because it is a rigid bar and does not flex with topography. Those growing on hills don’t want to use a wide machine, or the bar may hit the ground in one place while missing weeds in another.
Research reported in this publication was supported by The Organic Center and the Foundation for Food & Agriculture Research under award number Grant ID: TOCFFAR-EXT-002. The content of this publication is solely the responsibility of the authors and does not necessarily represent the official views of The Organic Center and the Foundation for Food & Agriculture Research.