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Soils Lab scientist Frank Forcella and Jim Eklund (on ATV) test the concept of sandblasting weed seedlings for selective control in corn. In place of sand, the grit was comprised of dried corn cobs ground to pass through a 20-40 mesh sieve. The gerry-rigged system is meant to simulate an imagined implement that would treat multiple rows simultaneously through pairs of nozzles aimed at the base of either side of each crop row. Submitted photo.

Forcella's idea may make controlling weeds a 'blast'

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By Tom Larson

Sun Tribune

ARS Soils Lab scientist Frank Forcella calls himself a "weed guy" who sits around with colleagues trying to figure out how to kill plants. The discussions get pretty creative, and sometimes they sound downright goofy.

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That was the first reaction when Forcella got this idea: "I was sitting around thinking, 'I wonder if we could use a sandblaster to kill weeds?' "

Well, as often happens with really smart people, a crazy notion turns out to be not so crazy after all. In fact, Forcella's idea has netted him and the lab almost $175,000 in grant money to explore it further.

In October, Forcella will receive the grant from the North Central Region Sustainable Agriculture Research and Education Program. Organic farmers are especially eager to know if using an "abrasive grit applicator" to control weeds in corn is practical in a large-scale operation, he said.

"What we've done so far is small scale - one row at a time," Forsella said. "(The grant) will help us do a full-scale demo model to prove if it works and calculate the economics."

If the plan continues to develop positively, organic farmers might one day be able to use corn gluten meal for the grit. It's potentially a win-win-win proposal: blasting the crops with corn gluten meal would kill the weeds, its high nitrogen content has led the organic industry to approve it as a fertilizer, and corn gluten meal also has been proven effective as a pre-emergence herbicide, Forcella said.

"Here, you get three bangs for your buck," he said.

Researchers also are encouraging producers to reap the carbon sequestration benefits of introducing biochar into their fields. Forcella's research will include experiments using gritty biochar as the abrasive.

"It's another incentive for farmers to use biochar and sequester carbon," he said.

Experiments have not been performed on beans, and Forsella said that currently the procedure is more suited for heavy-stalk plants in corn fields or vineyards. But researchers plan to look into just about every potential application.

Forsella, a research agronomist, began his professional career in 1979 and he joined the Soils Lab in Morris in 1988. He left for four years but returned to Morris in 1992. Alternative and sustainable agriculture has been a focus of Soils Lab research, and Forsella's research is especially relevant for organic farmers who don't use traditional chemicals to control weeds and pests.

The "sandblasting" is really a misnomer since the techniques have evolved considerably in the short time since Forcella and other researchers began working them.

First, they bought a sandblaster and rigged it up to an All Terrain Vehicle. They used ground up ag residue for the "sand." Ground up cherry pits and walnut shells were just a couple of the products fed through the machine, Forsella said.

The results have been encouraging.

According to Forsella, when corn cob grit was applied at the one-leaf and three-leaf stages of corn development, weights of weeds in small sample plots at the end of the growing season were reduced greatly. The reduction was equivalent to 87 percent weed control.

Corn yields did not differ from those in hand-weeded check plots and weed control was only 60 percent when grit was applied at the three-leaf and five-leaf stages of corn.

"Sandblasters are cheap and it was a way to make use of the residue," he said. "It's an alternative use of something that we'd normally throw away. If the weeds are small enough, they just shred."

The technique, if it proves feasible, probably will only appeal to organic farmers, he said.

"Round-Up works so well that conventional farmers would never go for it," Forsella said. "But if they can do this for a couple hundred bucks per acre, it might be feasible for organic farming."

The process is getting even more refined. It's only been used on corn plants between four inches and 12 inches in height, and so far there's been little damage done to the plants while the weeds have been effectively eradicated.

Forsella's received positive feedback from organic farmers. He talked to a group of organic growers during a seminar and the response was "tremendous," he said.

"One guy said, 'I can build that myself and I'm going to build one this summer,' " Forsella said, with a laugh. "I said, 'No, no, let us do the research first so we know we're not leading you up the wrong tree.' But the response was enthusiastic."

Carmen Fernholz, an organic farmer for 40 years, took a break from cultivating his corn earlier this week to talk about Forsella's research.

"I think, in theory, that if it can be put together, it would be great," Fernholz said.

Fernholz holds a half-time position with the University of Minnesota as an organic farming consultant at the Southwest Research and Outreach Center and is the contact for the Minnesota Organic Farmers' Information Exchange.

He's talked with Forcella about the research and said it's fitting the project has received substantial grant funding.

"It's a challenging theory, but it certainly does deserve further research," Fernholz said. "Frank does great work. That's the role of soil scientists and weed scientists. Crazy as an idea might be, that's how things evolve."

The Soils Lab will work on the abrasive grit applicator system with South Dakota State University researchers Sharon Clay, of SDSU's Plant Science Department and Teresa Hall, head of the SDSU Mechanical Engineering Department.

The promise of the project aside, it can't help by make a scientist feel a bit old, Forcella said with a laugh. He presents talks on the project and shows off the make-shift apparatus.

Most agriculture research today deals in genetics, not engineering better machinery, he said.

"It's a bit embarrassing," he said with a chuckle. "I show people the initial setup and it's a simple sandblaster with a funnel to hold the grit. It looks so rinky-dink, and I'm up there with the projects about things like DNA extraction. I think to myself, 'I'm at this level and here are all these young kids working with DNA and doing things with genes. I need to retire.' "

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