Dave Kohler stands behind soil conditioner equipment that includes the SpinWeeder he invented. The SpinWeeder (flat disk in the middle of the equipment), is manufactured by Northstar Attachments and sold by Oxbo International.

Dave Kohler stands behind soil conditioner equipment that includes the SpinWeeder he invented. The SpinWeeder (flat disk in the middle of the equipment), is manufactured by Northstar Attachments and sold by Oxbo International.

After years of sitting on a tractor to knock down vineyard weeds with an old grape hoe, only doing about an acre an hour and always causing some vine damage, Dave Kohler finally reached his breaking point. Nearly ten years ago, he’d had enough and was determined to figure out another way to mechanically weed the vineyard.

In 1992, he put his old Green hydraulic hoe away for good and used farmer creativity to develop a new type of weeder. After a decade of ­revisions and modifications, his device is now being sold commercially.

“It’s mind-blowing to sit on a tractor, tediously pulling a grape hoe,” said Kohler, who grows juice grapes in Pasco, Washington. “I could never get through the field without doing some damage to my vines, and if I got out of sync, I’d have to get off and start new.”

During those hours and hours of driving tractor, he had plenty of time to dream up a new approach that would use a horizontal wheel to mechanically weed. In his first attempt, he horizontally attached a packer wheel from an old Oliver grain drill onto the grape hoe. It worked long enough—about 1,000 feet before falling off—to prove that the concept would work. Each season, he improved his spinning wheel device and by 2008, he had two units mounted on each side of a field cultivator he designed and could operate at speeds of seven miles per hour. Satisified that the concept would work, in 2009 he showed his invention to Rankin Equipment in Yakima, Washington.

Northstar Attachments (Rankin’s manufacturing division) began ­manufacturing the new SpinWeeder last year. Patents are pending on design and utility. The in-row mechanical weeding system, marketed by Oxbo International, is generating a lot of interest from vineyardists in California and the Pacific Northwest. The device is now being tested for functionality in tree fruit orchards.

Spinning disk

The 18-inch-diameter weeder head wheel, with its 1-3/4-inch-deep flange, moves by the forward travel of the tractor and spins backward, tilling the soil and uprooting weeds about two inches deep. It can be angled for raised berms or flat ground. The smooth wheel has no sharp edges that can damage vines or spikes that can clog up with debris.

Kohler explained that the wheel head spins around the vines in a rolling sweep motion. As the wheel head spins around the vines, spring action makes it retract when it comes near the vine. The wheel creates a compression wave (similar to a Doppler effect), and the tilled soil is forced between the weeder head and vine base to provide a cushion to keep the wheel head from damaging the vine. It covers about 12 to 18 inches of the vine row.

The SpinWeeder was discussed during a session on weed control at the Washington State Grape Society’s annual meeting last November. Two growers shared their experiences with the new piece of equipment ­during the panel discussion.

Terry Charvet, a tree fruit and grape grower from Grandview, Washington, began farming organically in 1999. For years, he has used a Clemens grape hoe in his organic juice grapes for weed control, but Charvet said the hoe is slow, only covering two acres per hour, and requires high ­maintenance. Last year, he tried the new SpinWeeder and was impressed by its speed. He was able to make five passes during the season with the device and covered 70 acres of organic grapes by himself.

Low maintenance

“It worked really well once I got it adjusted,” Charvet said. “Maintenance is virtually nothing, and I could go seven miles per hour and cover about 3.5 acres per hour. I didn’t use the Clemens at all in 2010 and stuck with the spinner.”

In the past when using the Clemens grape hoe, Charvet said that 2.5 mph was as fast as he could go. “Just when I would get across my acreage, I had to turn around and do it again.” He likes the speed of the spinner, and adds that he can cover twice the amount of ground with the spinner in the same time as with the Clemens.

“The key is to get the weeds while they’re small, an inch or less in height,” said Charvet. “If you get behind, it’s a mess.”

Charvet noted that because the vineyard is organic, he uses only mechanical means to control weeds. He typically makes about five to six passes in a year for weed control, going until the canopy is large enough to shade out the weeds. However, weed pressure was heavier last year than normal due to the spring rains, requiring an extra pass or two.

Charvet was also pleased with how the SpinWeeder worked in a new vineyard planting. “It went right around the new vines without any ­damage.”

Albert Don of Grandview’s Wyckoff Farms also used the SpinWeeder last year to knock down weeds in the company’s organic vineyards. “It physically knocks small weeds down, though you do have to be more timely with it because is doesn’t work as well if the weeds are large.”

Don said that he averaged 3.5 to 4 mph with the spinner, depending on the weed pressure. He runs a double-sided, dual unit at Wyckoff, which allows him to slow the speed down a bit but still cover a lot of ground. He advises growers to use a front- or side-mounted weed spinner so that drivers can see and operate the tool better than if it’s rear mounted.

He found the SpinWeeder to be less disruptive to a vine’s root system than a cultivator or Pellenc Sunflower weeder, both of which can mark trunks if the equipment is set to be too aggressive. He believes the ­spinner works best if the vine row is on a small hill or berm.

The SpinWeeder comes in three models: mounted on a three-in-one soil conditioner; a fixed frame; and an adjustable hydraulic frame. It’s available with single or dual spin weeders to allow one or both sides of the vine row to be weeded. A dual weeder on a hydraulic frame tool bar, with two half sweeps and S tines, retails for about $8,500. A single weeder head, without the tool bar, costs around $2,000.