Corn School: Could wildfire smoke help corn yields? It's hazy

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There’s a long list of known ways in which wildfire smoke can negatively affect corn and other crops, but could the overall effect of the smoky haze in summer potentially be positive for yields?

It’s a complex question to answer, says Dan Quinn, extension corn specialist with Purdue University, in this Corn School episode recorded at CropConnect at Winnipeg, Man.

Looking back at 2023, much of the U.S. Midwest, Ontario, and Manitoba saw better than expected corn yields. The U.S. Department of Agriculture figures the national average yield hit a record high of 177.3 bu/ac, while Quinn’s home state of Indiana set a new state yield record.

All of this coincided with an above-normal number of days with smoke-filled skies, which led Quinn to investigate a possible connection.

On negative side, smoke clearly reduces solar radiation, similar to shade or cloud, which leads to lower rates of photosynthesis. Pollutants or chemicals in the smoke, such as ground level ozone or  can also be toxic or stressful to the plants, he notes.

But smoke can actually scatter sunlight to improve light efficiency in the crop canopy, says Quinn. Lower air temperatures and leaf surface temperatures may also be beneficial for plants stressed by heat or dry conditions, he notes.

“In Indiana and the Midwest, we were very hot and dry in June. And then when the wildfire smoke came in, the temperatures dropped pretty significantly, along with the transpiration rates. The water loss of the crops dropped, leaf surface temperatures dropped, and it’s almost like those crops kind of took a breather,” says Quinn.

Smoky conditions later in the season, during reproductive stages of the crop, may be more detrimental, he says, citing research that shows cloud cover during pollination hurts yield.

In the future, Quinn says he’d like to study whether there are any differences related to CO2 levels on smoky days, but he notes C4 crops like corn are less sensitive to CO2 fluctuations than C3 crops like soybeans or canola.

From an agronomic perspective, it’s impossible to predict when and where it will be smoky, but he suspects there would be differences between corn hybrids and row spacings/canopy coverage when subjected to the same smoky conditions.

“That’s the challenge of wildfire smoke. It’s very complex, with the fact that there are positive and negative impacts. I think it really comes down to what state the crop was in at the point in time it comes and then also the duration of the wildfire smoke, but there’s a lot more we still have to understand,” says Quinn.

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