Impact of smoke on crops is more than a little hazy

Field crops are impacted but the science is scarce and the subject is very complex, say experts

Smoke from wildfires can definitely delay plant growth but the precise effect on crops and pastures is largely unknown because very little research has been done.
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After watching smoke choke the skies over their fields for three years running, producers in Alberta are increasingly asking what effect it’s all having on their crops.

But unfortunately, little research has been done on the phenomenon.

Jeremy Boychyn. photo: Supplied

“It is so plant and environment specific,” said Jeremy Boychyn, research extension agronomist with Alberta Barley and Alberta Wheat.

“There are a number of factors that affect how it affects growth.”

After talking to scientists and reviewing research literature, Boychyn has some answers but nowhere near a complete picture.

One of the factors affecting growth is the amount of pollutants in the air and how they affect stomata (tiny openings in the surface of the leaf and other parts of the plant that open and close to bring in the carbon dioxide and release oxygen).

“If there’s an increased amount of pollutant, some plants will shut their stomata,” he said.

As well, when the air is very smoky, there will also be reduced photosynthesis. Some studies have shown smoke reduces the amount of photosynthetic light available to the plant. Increased carbon dioxide and particulates in the air can lead to light refraction.

But it’s a complicated equation, determined by how close the crop is to a fire, how thick the smoke is, and how much light is being affected. Crop varieties and staging are two other variables that can affect plant growth.

“It’s so complex that it is hard to get an answer. It’s all hypothetical,” said Boychyn.

Since this year’s smoke was bad at the end of May and beginning of June, it may affect cereal’s spikes and kernels.

In some cases, smoke has increased yield capacity, but only to a certain point.

“There is no data on agricultural crops,” said Boychyn. “There’s nothing I can find and I’ve reached out to a number of people.

“This is the third year in a row that we’re dealing with this and it begs the question: Do we need to know what to expect when we’ve got this type of scenario coming in?”

Given the rising incidence of wildfires and the haze they spread across the Prairies, Boychyn said it’s likely researchers will begin studying the effects of smoke on crops in the western Canadian context.

Raju Soolanayakanahally agrees.

The plant physiologist with Agriculture and Agri-Food Canada in Saskatoon has a background in forestry. Some lab studies have been done where smoke is artificially blown on a plant, but there have been no field studies, he said.

But smoke does appear to affect plant growth, said Soolanayakanahally.

Raju Soolanayakanahally. photo: Supplied

“On a cloudy day, the crop growth can be really slow as far as emergence or other things are concerned,” he said.

Last year’s smoky days in Alberta happened when the crops had just established themselves.

“It was just before flowering or heading in wheat and canola,” he said. “We started to get a big smoke and there was delay in the flowering time in a lot of crops in Alberta.”

When smoke comes in July or August, it blocks stomata. Smoke makes the air dry, and as soon as the air gets drier, the plant tries to avoid losing moisture and closes their stomata, which reduces the plant growth on any given day.

“When smoke goes on for a long time, the plant growth is very minimal, versus a sunny day when it continues to grow,” he said. “Last year, there was delayed flowering by 10 to 12 days in Alberta.”

A lot of smoke can promote seed germination, and long periods can lead to uniform establishment. But with this year’s dry conditions, there would likely be no effect, said Soolanayakanahally.

“Drought is a big factor on seed germination, but whether the smoke will help or hinder, we do not have that much information on that regard,” he said.

“If there was moisture, the crops would have come along really nicely, that would have helped us understand emergence, but we are facing a severe water shortage. It may not have any influence on emergence this year.”

He also said that smoke would have little effect on herbicides.

However, smoke contains toxic chemicals that destroy chlorophyll on a plant, and can really hurt photosynthesis, he said.

Researchers in Australia — where massive wildfires are increasingly common — have done some studies on their effect. But most of that research looks at the effects of the fires themselves on plants and soils.

About the author


Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."



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