From corn and soybeans to wheat and canola, crops can respond differently to wildfire smoke depending on growth stage, weather conditions, and smoke intensity.
Wildfire smoke is becoming a more frequent challenge for farmers across many agricultural regions of the United States. According to Penn State Extension, smoky conditions now occur during nearly 20% of the growing season, with July and August experiencing the highest number of smoke events. Unlike people, who can reduce their exposure by staying indoors, crops remain exposed throughout the season.
Wildfire smoke contains a mixture of gases, fine particles, volatile organic compounds (VOCs), and biological materials. Together, these components can influence crop development by affecting sunlight, air quality, temperature, and atmospheric conditions.
The extent of the impact varies depending on the crop, its stage of growth, the density of the smoke, and local weather.
One of the biggest effects of smoke is how it changes sunlight. Lighter smoke increases diffuse light, allowing sunlight to reach deeper into the crop canopy and improve photosynthesis in lower leaves.
However, dense smoke reduces the total amount of sunlight available, slowing photosynthesis and limiting plant growth. This can be especially harmful during reproductive stages, when crops are most sensitive to reduced light.
Smoke can also lower daytime temperatures and reduce water loss through transpiration, helping preserve soil moisture during dry periods. On the other hand, particles settling on leaves may block gas exchange, decrease photosynthesis, and slow crop development.
Prolonged smoky conditions may also delay the accumulation of growing degree days, increasing the risk of frost damage in regions with shorter growing seasons.
Wildfire emissions can contribute to ozone formation, which may injure plant tissues, reduce yields, and make crops more vulnerable to pests and diseases.
Observations from the 2023 Canadian wildfires showed reduced solar radiation across parts of the Midwest, but corn, soybean, wheat, and canola yields generally remained above average because the heaviest smoke occurred when crops were less vulnerable. Researchers continue to study the long-term agricultural effects of wildfire smoke.
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