Machines potentially offer new options for organic growers

By STEVE BROWN

Capital Press

Researchers are looking for better -- and more cost-effective -- ways to control weeds on organic farms.

Mark Siemens, of the University of Arizona, is testing a thinning device that turns a sprayer on and off to leave the desired plants, Fennimore said.

His prototype has been tested spraying sulfuric acid, herbicidal vinegar or fertilizers.

"It has proven successful, and we're now developing a second-generation prototype," he said.

After tests this fall, commercialization could follow, Siemens said. It's simple mechanically, but the electronics are "fairly complicated but straightforward."

He said similar machinery on the market costs about $23,000 per seed line, and his machine should be in the same price range.

"We developed it with the organic grower in mind, maybe for a custom operation or lease operation," Siemens said.

Steve Fennimore, extension weed specialist at the University of California-Davis, has been evaluating nonchemical treatments for row crops.

"The research is of particular interest to organic growers, but conventional growers are also concerned," he said.

A prototype machine Fennimore tested from a British manufacturer uses a video camera mounted on a cultivator. The camera captures images of the crop row and sends them to a computer for precise alignment.

The blades of the cultivator then pass down the row and remove weeds -- ideally without damaging the crop.

However, he said, the machine was "a bit disappointing" in field tests of transplanted lettuce, tomatoes and celery.

The machine was also tested as a lettuce thinner. California growers spend $30 million a year thinning lettuce, Fennimore said. "We're aiming to reduce that by half."

Again the results didn't pencil out. The device reduced the yield by 5 to 10 percent.

Fennimore is also building a machine that will steam soil as an alternative to fumigation.

Research grants from the ag industry and the USDA are supporting this work.

"Research that advances our knowledge of the biology, ecology and management of weeds is fundamental to success on any farm, and it is vital that we do more of it," Fennimore said. "Scientific investigation gives us a broader base of tools that can be used successfully -- regardless of the size of the operation or whether a farmer chooses conventional or organic growing practices."

In a survey conducted by researchers at the Rodale Institute, 85 percent of U.S. organic growers said they use at least three weed-management strategies, and most use six.

The top six practices are hand weeding, mechanical control, mulches, cover crops, crop rotation and dense planting. These practices remove weeds, prevent them from being competitive or, in the case of crop rotation, inhibit weeds that prefer the growing conditions associated with certain crops.

"Other than herbicides, the toolbox of available weed management practices is the same for all growers," he said. "Effective weed control requires an integrated approach based on knowledge of each crop and the weeds that threaten it."