On a summer morning at the University of Idaho’s Parma Research and Extension Center, the scent of a campfire fills the air.
Just before dawn, Plant Sciences Professor Mike Thornton started a blaze in a black steel barrel equipped with two cold smoke generators. On top of charcoals, he tossed in a special batch of plant clippings.
“We’ve got ground up pine trees; we've got some walnut," he said.
The resulting concoction is similar to smoke produced from wildfires.
“We're trying to get to a smoke concentration that would mimic some of the heavier smoke days we have here in this valley," Thornton said.
For three hours every morning over the course of six summer weeks, Thornton shot the smoke from the barrel down tubes and into mini hoop houses, perfectly sized to envelop a row of potato plants. Inside the cloth and plastic-covered enclosures, the green leafy plants were swimming in a very fine, barely-noticeable haze. Control plants were not exposed to smoke.
This summer offered southern Idaho farmers a respite from wildfires, but smoke is expected to cover Idaho more frequently with climate change. Thornton teamed up with Boise State University chemistry professor Owen McDougal on a two-year study to unravel the potential consequences for Idaho, a state responsible for a third of U.S. potato production.
The project is funded by $125,000 from the federal Specialty Crop Block Grant program.
It all began with observations from farmers, and those in the potato industry, themselves.
Randy Hardy has grown potatoes and other crops in Oakley for more than 50 years. He said he didn’t dwell on wildfire smoke for much of that time – it was just another factor in the weather. But that changed one summer a few years ago.
“When you get these large fires like we had in California, and Washington, and Oregon that move in here and they're here for three or four weeks, that's when we started to see things that weren't normal," he said.
The sun was blocked during the day, turning the sky into an apocalyptic scene, and nighttime temperatures didn’t drop to the lows that are ideal for the crop.
The potatoes were in their bulking stage, when the leafy parts stop growing and shoot all their energy underground to beef up the tubers.
Hardy said during the prolonged smoke, he would dig up the plants to check on the bulking.
“It’s like that process just stops, and I mean just stops," he said. "You go two or three weeks and you're digging in potato plants that are showing no advancement.”
Hardy wasn’t the only one seeing this; he said lots of farmers were talking about it.
However, determining whether the chemicals in wildfire smoke directly influence potato yield and quality, or if other factors such as reduced sunlight or hot, dry weather play a role is a challenge, said Tim Waters, a professor and vegetable specialist at Washington State University Extension.
He said it's tough to design a study that can untangle those variables. Smoky conditions would be hard to replicate in a greenhouse and shielding actual wildfire smoke away from control plots wouldn't work either.
“We just can't influence the air in the entire vicinity," he said.
Waters thinks the complexity has contributed to the limited research on smoke's effects on crops, other than studies on wine grapes. Research has found it can make the wine taste ashy.
Waters is not involved with the Idaho study, but said its method of blowing smoke into chambers seems promising. When the research is peer reviewed, he’ll look to see how Thornton’s team accounts for changes in CO2, solar radiation and humidity, to make sure those didn't skew the results.
In the first year of the research, those other variables might've had an effect. The plastic covers raised humidity levels and increased the temperature under the enclosure. To isolate those influences from the smoke, Thornton added shade covers and fans this summer.
Looking at the plants at the U of I research farm, Thornton said the effects aren’t visually obvious. Abnormalities from last summer’s field trials were only noticeable after the potatoes were analyzed.
“We saw that the smoke exposure plants had smaller potatoes and they had potatoes that were more misshapen," he said.
They had knobs that would make them tough to sell to processors. Thornton estimated it affected yield and shape by about 10%.
Still, farmers like Hardy are skeptical there’s much they can do to dodge the smoke.
One idea the research may be able to provide is whether certain potato varieties handle it better.
“They can say, 'Hey, can I grow this variety and be less sensitive to smoke damage going forward,'" Thornton said.
So far, it seems Clearwater Russets might be faring better than Russet Burbanks, the quintessential Idaho potato.
The U of I research team is nearing harvest later this month of up to 1,000 pounds of potatoes. Some will be sent to storage; others processed into French fries and delivered to a lab at Boise State, where they'll be analyzed for amino acids, fat and sugar content. More simple sugars often mean increased browning, threatening the golden yellow ideal.
Even subtle changes in these factors could significantly influence Idaho's billion-dollar annual potato revenue, an industry that expands to approximately $5 billion when processors are factored in.
"We're known for producing consistent quality potatoes," Thornton said, "and we want to continue to be able to do that, even after smoky conditions."
Since starting this research, he’s heard from farmers who grow other crops like onions. They’re similarly curious about how smoke could be affecting their crops, and are craving answers, too.
Find reporter Rachel Cohen on Twitter @racheld_cohen
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