Plow it, spray it, crowd it, fry it - There are many ways to kill weeds, pests and diseases – and there’s a new technology emerging that allows farmers “dry clean” their fields, so to speak.

The Propane Education & Research Council (PERC) recently unveiled an eco-friendly solution for “soil disinfection” with the propane-powered soil steamer. PERC says the machine can, “address one of farmers’ biggest challenges in modern agriculture: how to effectively eliminate weeds, soilborne pathogens, and nematodes without relying on chemical pesticides.”

The machine’s banded steam design targets the top 1-2 inches of soil, the critical zone where weed seeds germinate, providing 80% weed control for both conventional and organic crops, says Mike Newland’s Mike Newland, PERC’s director of agriculture business development. The system can cut weeding labor costs in half, increases yields and reduces the dependency on harmful fumigants and herbicides, he says. 

PERC cites studies showing the steamer manages 90-95% of annual weeds such as purslane and pigweed, and controls major soilborne diseases like fusarium, pythium and verticillium. When used for lettuce cultivation, it has been shown to increase yield by 25% in fields affected by lettuce drop. 

The technology also provides an estimated 73% reduction in weeding time compared to traditional herbicides.

Years in the Making

Steaming has been used successfully before to disinfect soil but was too costly and time-consuming for large-scale operations. Steamer increases the size of crops such as lettuce and carrots and enables shorter crop rotation intervals, allowing for more frequent planting of high-value fruits and vegetables, Newland says.

At the current time the technology isn’t cost effective for production fields with thousands of acres. Newland says he can’t speculate if the steam would harm beneficial insects or soil organisms that many no-tillers work hard to protect. 

Newland credited Dr. Steve Fennimore, a weed management specialist at the University of California-Davis research station in Salinas, Calif., for researching the technology here and in other parts of the world. PERC helped fund some early research. Newland says Fennimore spent much of his career, “trying to figure out exactly the appropriate temperature and appropriate duration of that temperature in soils to be the most beneficial.”

There’s been different iterations of field equipment with steam applications that Fennimore designed, and he also brought some equipment over from Europe to test, Newland says, but none of it was as effective enough. Fennimore approached PERC a couple of years ago to partner on a steam-related project, and Fennimore and his UC-Davis team developed the current machine from scratch. 

When the buildout date arrived, the concept was taken to Valley Fabrication in Salinas, which makes custom field equipment for high-value crops in the region. “It does a great job of doing exactly what Steve and his team were hoping for. And the results are tremendous, so we’re excited about it,” Newland says.

“There’s steam units in other parts of the world. But this unit is very unique because it doesn’t move, stop and steam a block of ground, if you will. It’s constantly moving, and I think that very unique feature allows for Steve to control that temperature output and the duration of that temperature.”

Technology Promise

The original unit is mostly used in the lettuce industry in Yuma, Ariz., and testing is being done in carrot and strawberry crops. Valley Fabrication is preparing to build the second machine, which has already been spoken for. Newland declined to say who purchased it. 

While the technology has a lot of promise, Newland says the machine is probably too expensive to run on row-crop fields with thousands of acres. He predicts most of the machines, for now, will be custom built because there is, “just enough variation in application or cropping techniques that nobody will want to pay for them to sit in a barn for most of the year.”

Newland isn’t ruling out the steam technology playing a future role controlling weeds and pests on production farms. 

“If it moves to the Midwest,” he says, “it would probably be for the toughest conditions, just from a cost-per-acre standpoint. We hate to think we’d want to do every acre for herbicide-resistant weeds. But we may reach a point where different measures are needed to control those things.”