Gas burner beats weeds in vegetable fields

It was while visiting an organic vegetable farm in Switzerland that he heard about the practise of burning weeds out with a gas burner, says Mr. Skye Fehlmann.

To win the fight against weeds, he and his partner, Mr. Dawie Badenhorst, use this method on fields where seeds have been sown that take longer to germinate, such as carrots and coriander.

They use two devices: one that you carry around by hand, and one that is drawn with a tractor. The weeds are scorched a week after the sowing has taken place. “You are just working on the surface, so everything below ground is safe,”says Skye. “You can’t do it once the seeds have germinated, since you’ll scorch the seedlings in the process.”

To burn weeds out with a gas burner was a common practice in the 1950s and 1960s, but it became unpopular in the 70s due to high gas prices and the availability of cheap chemical alternatives. Fears about the impact of chemicals on the environment and the development of resistant weeds, however, has seen the practice gain popularity again, especially in Europe.

Mr Dawie Badenhorst and Mr Skye Fehlmann.

The devices

The burner that works by hand is a normal burner that is used to burn tar. Skye bought it from his co-op. The burner pulled by tractor was built for them by Mr. Richard Ruster of Philippi Boeredienste (Philippi farm services in Philippi, South Africa). “It’s a simple concept, like attaching a gas stove that works under high pressure onto a framework and pulling it over the fields,” says Skye.

The burner consists of a flat metal pipe that is closed on the one side. Gas is released from ten small evenly spaced holes in the pipe. Four bolts are used to attach the pipe to a square metal shield that is open at the bottom to allow the flames to move over the earth.

The 1, 2m wide device is attached to a grubber with two chains, one either side of the shield. The chains also help to control the height at which you burn. A space is made for the gas bottle in the middle of the grubber. A high pressure valve controls the pressure at which gas is released.

The grubber has a large nail on either side that loosens roots of weeds while the fields are being burned. For best results, you need to move over the field slowly so the weeds are exposed to the flame for a few seconds at a time. The flame ups the temperature in the weeds so that the walls of the cells burst. The results are visible a few hours after it’s been burned.

Skye and Dawie are very satisfied with the results. Where they had to manually hoe out weeds in the past, they can now wait up to 20 days after sowing, when the seedlings are stronger and not as easily disturbed by the hoe. This method also saves them time and effort.

A metal shield is used to control the flames that come out of the burner.
A metal shield is used to control the flames that come out of the burner.

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