Technology provides option to replace potentially limited chemical fumigation
By WES SANDER
Researcher Brad Hanson wants to bring farmers in California a new tool to cope with increasing suburban encroachment and ever-more-stringent regulations.
Hanson grew up working on the family farm in Iowa, where his father grows commodity crops. It's a background that helps him identify with the everyday challenges of food production, Hanson said.
It has driven him to help develop a system of steam fumigation for orchard replanting. Along with plant pathology specialist Greg Browne and weed-control specialist Steve Fennimore, Hanson is using his lab at the University of California-Davis to work out the kinks in the new tool, which could help mitigate impacts of the state's environmental rules.
"What I want to do is give growers an option to efficiently grow a crop in their entire field," Hanson said.
The researchers are experimenting with an auger that drills into the ground and injects steam. Because the blades are short, they don't remove dirt from the hole, instead only churning it.
After several minutes of steaming and churning, the soil is heated to nearly 200 degrees Fahrenheit, hot enough to provide a sapling with two to three months without pests around the young roots, Hanson said.
"The whole idea is, if we can treat this minimum amount of soil, we can make it economical and give enough pest control to get those trees off to a good start," Hanson said.
It's for economic reasons that the system doesn't treat most of an orchard's soil, the way chemical fumigation does.
"Steam is expensive," Hanson said. "We're using a lot of fuel. We can't treat acres and acres with heat. It's cost-prohibitive."
The system therefore lacks the potential for replacing chemical fumigants, Hanson said. But it can help many farmers stay in business when buffer zones prevent fumigation on large sections of land abutting urban areas.
Orchard growers have long injected methyl bromide into the soil to prepare it before replanting trees, clearing it of pathogens, weed seeds and nematodes. With that chemical largely phased out to reduce ozone-depleting emissions, growers in California and Washington are hoping for approval of methyl iodide as a replacement.
The two states are among the few that conduct their own approvals instead of deferring to USDA's registration process for commercial chemicals. California's registration proposal, which awaits a final decision after being introduced earlier this year, proposes buffer zones of up to a half-mile around sites like schools and hospitals.
In some cases, that could mean most of an orchard, Hanson said.
The steaming technique could also prove a viable option for organic growers, who can pass on higher cultivation costs to higher product prices, Hanson said.
"Our target is not to replace fumigants per se," Hanson said. "Our target is to have treatments for areas that cannot be fumigated, and to have an alternative for when fumigants are not available."
Viable alternatives could eventually replace chemicals, but not for another decade or two, Hanson said.
"Strictly from an efficacy standpoint, I think our productivity would suffer too much if we were to stop using fumigants tomorrow," Hanson said.
The researchers are also working on steam fumigation for row crops like strawberries. They're considering a self-propelled machine that picks up soil, heats it inside a chamber, then deposits it in beds.
Such ideas are "not a panacea by any stretch," Hanson said. "In the next few years, if we can replace a few percent of the fumigants used in (farming), we'll be on our way to having some success."
Occupation: Weed-control researcher, University of California-Davis
Hometown: Inwood, Iowa
Education: Doctorate in plant science, University of Idaho, 2004
Quote: "What I want to do is give growers an option to efficiently grow a crop in their entire field."