Test: Electro weeder puts weeds under high-voltage
After three years of experimentation, the electric weeder from Dutch manufacturer Andela Techniek en Innovatie is ready for practical use. With a strong electric shock, it kills weeds entirely, roots and all.
It crackles and smells a little, but that’s all that hints something is happening behind the tractor with Andela’s Electro Weeder. Upon closer inspection, you can see small flames under the scrapers, which in this case follow the sides of the plant beds. Weeds that are well hit start to darken after just a few minutes.
On the plot in the Dutch region Noordoostpolder where Future Farming witnessed the machine in action, it was mainly dealing with annual bluegrass. On a patch where that grass had received a shock of several thousand volts three weeks earlier, it was significantly dead. Almost no pulling force is needed; the large power requirement comes from the generator that produces the electricity.
Variable power
The Kubota M7172 tractor used with the machine produces a maximum of 175 hp and had no trouble with the Electro Weeder. The tractor seems oversized for the 3-meter version, but keep in mind that the rear generator can deliver about 150 kW, or around 200 hp. The generator supplies more power as the machine draws more current, which depends on the amount of vegetation touched by the sensors and the moisture in the ground they drag over. With fewer plants, the machine draws less power. If there are more, the Andela demands more. The soil must be dry on the surface (gray); while it can work on darker soil, it requires disproportionately more electricity.
The variation in weed coverage on the plot wasn’t significant enough to affect the tractor. If there had been a blanket of weeds or grass, a 200 hp tractor might have struggled. Working width also plays a role: a 3-meter frame was used for carrots, but a 6-meter width is available, which automatically draws twice the power.
High-Voltage weeding
Using a strong electric current to kill plants is a known phenomenon. This technique has been around for decades. In the early 1980s, experiments were conducted in the Netherlands using electricity to kill bolters in sugar beets. The concept is that weeds receive an electric shock that heats the plant to at least 60 degrees Celsius. This causes the cells to burst, proteins to coagulate, and the plant to die.
The landscape management sector has years of experience with the English Rootwave, which is used to combat invasive species like Japanese knotweed. In agriculture, the Swiss Zasso, marketed by CNH and the Belgian Group Verschueren, is used to tackle difficult-to-control weeds, like nutsedge, which is nearly impossible to kill chemically. While electrocution can effectively reduce it, it doesn’t eliminate it in one go. Persistent root weeds aren’t completely killed if they root too deeply. The drier the soil, the better the root is killed, as electricity follows the path of least resistance and is difficult to direct all the way to the root tip.
The Nucrop is another example of an electrocution machine, specifically used as a haulm destroyer in potatoes, and it seems to work well. The difference is that the Nucrop is the only one that uses a conductive fluid.
Andela also experimented over the past three years with potatoes, testing the effects on seed potato viability in combination with topping. The preliminary conclusion is that it’s crucial for all stems on the ridge to be hit. In that case, the potato plant dies quickly without the current affecting the tuber. Previous studies elsewhere also showed that electrocution doesn’t harm soil life.
Half the machine electrified
The voltage that the inverter boosts from the generator’s alternating current is adjustable, as is the frequency. Voltage, amperage, frequency, and the duration of exposure form the mix that determines its effectiveness, says Paul Andela, the machine’s designer. And at the same time, this is somewhat of a trade secret. In practice, we’re dealing with voltages of several thousand volts, which calls for careful attention to safety.
The implement frame consists of two levels: the lower frame, where the electrodes are attached, is insulated from the upper frame. The lower frame and electrodes are fully electrified. When the generator is running, you must stay away from it. For safety, no one should be allowed in the field while the machine is working, and you should only get off the tractor after turning it off. Thanks to grounding with two coulter discs, the frame immediately loses its charge once the generator stops. On the other hand, there’s no sound, sight, smell, or taste to indicate anything is happening. With a frame that can carry thousands of volts, it’s important to be cautious and know what you’re doing. If it starts raining: stop. According to Andela, CE certification is nearly complete.
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