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Growers reaching back to soil steamers

October 2023

David Paulk, owner of Sassafras Creek Farm in Leonardtown, Md., poses with his steam generator, which he uses to fight soil-borne diseases in his high-tunnel crops. (Photo by Jonathan Cribbs)

by Jonathan Cribbs, The Delmarva Farmer

LEONARDTOWN, Md. — To fight soil-borne diseases, weeds and insects on produce crops, some farmers are reconsidering 19th century technology with the hope that the past may hold forgotten solutions to pesky, present-day growing challenges.

Steam generators can be used to heat crop soil, killing or deactivating harmful elements such as nematodes, fungi and viruses, and it’s a viable alternative to the use of chemicals and fumigants in agricultural settings, including greenhouses, high tunnels and open fields, several regional farmers said. In recent years, a small but growing number of them have turned to the machines to avoid non-organic treatments.

“It’s extremely effective,” said David Paulk, owner of Sassafras Creek Farm in St. Mary’s County as well as a recently purchased steamer that he enthusiastically deploys inside high tunnels to protect crops, such as tomatoes. “At the soil-borne diseases, it’s good at suppressing them. It’s like everything in agriculture; it’s never 100 percent, but it certainly slows down that problem and reduces the damage to the crops for sure.”

Soil steaming began in an agricultural context in Germany in 1888 and was picked up in the United States in the following decade where it became a popular agricultural tool until chemical pesticides and fumigants such as methyl bromide joined the market in the 1950s. The federal prohibition of methyl bromide in 2005 led to a renewed interest in soil steaming.

Paulk tends to cilantro in a high tunnel on his farm that has been treated with a soil steamer, which are becoming more popular with a small but growing number of farmers. (Photo by Jonathan Cribbs)

By burning diesel fuel, a steam generator heats water and produces steam applied for several hours to the soil covered by a tarp, raising it to temperatures between 160 and 212 degrees, according to the University of Missouri. The steam pasteurizes the soil, destroying cell structures and proteins in problematic weeds, diseases and other issues. Paulk, an organic farmer, was introduced to the machine while visiting another farm in New England that had turned to soil steaming to manage weeds. Around that time, he discovered root-knot nematode on his high-tunnel tomatoes, a growing problem in Southern Maryland as temperatures rise.

“There really aren’t ways to treat that — nothing organically — other than steam, and there’s very little, as I understand, in the conventional world to apply chemicals to the soil to do that because (regional farmers) are all struggling with it,” he said.

Convinced, he drove to Canada in 2018 and bought an outmoded, decades-old steamer to give himself a relatively cheap trial with the equipment. In 2020, he replaced it with a brand-new machine for roughly $25,000 from the Sioux Corp., a South Dakota company that designs steam generators and other equipment for use across many industries, agriculture included. The machine proved its value by boosting yields and reducing cost, he said. He could grow, say, spinach in high tunnels without the steam generator without the machine, but would it be cheaper?

“No, because it would be full of weeds, and you couldn’t afford the labor bill to try to get people to pick the harvest, pull all the weeds out of it, both in the field and also in the wash and pack station,” he said. “You would just be going upside down. So it does pay for itself in terms of the yield and the quality of the crop that comes out.”

Nearby, other farmers have caught on as well. Elvin Weaver launched a business with his own Sioux generator, Loveville Soil Steaming Service, for regional farmers. One of his customers, Chris Field, learned about the service after speaking with Paulk. The Gilbertsville, Pa., farmer was struggling with chickweed in his high-tunnel produce operation, and while his farm isn’t Certified Organic, it follows organic tenets, Field said.

“Chickweed is hard to hoe and kill, and even if you do hoe it well, it can come back with a vengeance,” he said.

For about $4,000, he said he recruited Loveville to visit his 7-acre farm last fall and steam three high tunnels used for several crops including tomatoes, spinach, arugula and mache, which he sells at a premium in New York City. The math penciled out, and he said he was pleased with the work, which took a day.

“The crop quality that we got out of those houses for the winter for greens was incredible,” he said.

Nationwide, steam generators are becoming more popular as word spreads among competitive farmers, said Jon Erlandson, the company’s business development manager. The company’s generator’s are also low-pressure machines, making them safer than older models. Consumer interest in organic foods grown without chemicals is also boosting interest in the equipment.

“The consumer is ever more interested in organic vegetables and organic, healthier food,” he said. “This is something that has been around for a century. We’re just making it simpler to use and safer.”

Soil steaming can have drawbacks, however. It can harm beneficial microorganisms in soil that may need to be revitalized through compost or other means after steaming. Field believes he raised odd, misshapen carrots last winter, he believes because the steaming killed microbes leading to a release of nitrogen in the soil — useful for most of his crops, but not carrots. Regardless, he’s considering buying his own generator.

“It’s really an amazing thing,” he said. “If I didn’t have two young children and a crazy busy farm, it’s a really good opportunity to set up a business regionally.”

Paulk said he’d like to see more agricultural organizations such as soil conservation districts and Farm Bureaus buy generators that could be lent to farmers.

“It’s a great machine,” he said. “Word’s getting out there.”

The Delmarva Farmer is a weekly newspaper for farmers, farming and the agriculture industry in Delaware, Maryland and Virginia.