Reduced sunlight, air quality concerns, and livestock stress are creating new challenges for Ontario producers as wildfire smoke drifts across agricultural regions.
Ontario farmers are becoming increasingly familiar with hazy skies as wildfire smoke drifts across the province. While much of the public focus remains on human health and visibility, the agricultural impacts are also drawing attention as smoke affects crop development, livestock wellbeing, and outdoor work conditions.
With active wildfires continuing to generate smoke across parts of Ontario, farmers are being forced to balance field operations with concerns about air quality, animal welfare, and potential crop performance. Environment and health officials have repeatedly warned of elevated particulate levels during smoke events, particularly in areas where smoke settles close to the ground.
What Wildfire Smoke Means for Corn and Soybean Crops
The impact of wildfire smoke on crops is complex and depends largely on smoke density, duration, crop growth stage, temperature, and moisture conditions.
One of the most immediate effects is reduced sunlight. Smoke particles scatter and block incoming solar radiation, limiting the light available for photosynthesis. Researchers have found that corn is generally more sensitive to reduced sunlight than soybeans because corn uses the C4 photosynthetic pathway and has a greater demand for intense sunlight to maximize growth. Soybeans, which use the C3 pathway, tend to tolerate lower light levels somewhat better according to the extension specialists at Purdue University.
For Ontario's corn crop, prolonged periods of heavy smoke during key growth stages could potentially reduce photosynthetic activity and limit yield potential. Reduced photosynthesis may also lead plants to draw on stored carbohydrates later in the season, potentially increasing susceptibility to stalk weakness or lodging.
However, the picture is not entirely negative.
Scientists note that wildfire smoke can create more diffuse light, allowing sunlight to penetrate deeper into the crop canopy. In some situations, this can improve photosynthesis in lower leaves and partially offset the loss of direct sunlight. Smoke can also slightly reduce leaf temperatures and ease water stress during hot weather.
The greatest concern arises when smoke persists for extended periods and coincides with critical reproductive stages, such as corn pollination or soybean flowering and pod fill. During these periods, consistent sunlight is particularly important for maximizing yield potential.
Ground-Level Ozone May Present Additional Risks
Wildfire smoke contains a mixture of gases and fine particulates that can contribute to the formation of ground-level ozone.
Ozone is harmful to plants because it enters through leaf stomata and damages plant tissues, reducing photosynthetic efficiency. Research cited by crop specialists suggests elevated ozone exposure can negatively affect both corn and soybean performance, particularly when plants are already dealing with heat or moisture stress say experts from Bayer.
Although most Ontario crops are unlikely to suffer major losses from occasional smoke events alone, repeated exposure throughout the growing season could increase crop stress and reduce productivity in some regions.
Effects on Livestock and Poultry
Crop production is only part of the equation. Livestock producers must also consider how smoke affects animal health.
According to the Ontario Federation of Agriculture, smoke exposure can cause respiratory stress in livestock, reduce feed intake, and negatively affect productivity. Animals experiencing prolonged smoke exposure may exhibit reduced performance, increased discomfort, and greater susceptibility to other health challenges.
Dairy cattle, beef cattle, horses, sheep, goats, and poultry may all experience varying levels of stress during poor air quality events. Young animals, older animals, and those with existing respiratory conditions are especially vulnerable.
Smoke may also contaminate open water sources and feed supplies if ash becomes present. OFA encourages farmers to regularly inspect feed storage areas and evaluate water quality when smoke events persist.
Tips for Protecting Livestock During Smoke Events
Producers can also reduce risks to their animals by taking several practical steps:
- Ensure constant access to clean, fresh water.
- Provide shade and ventilation during hot weather.
- Minimize unnecessary animal handling or transportation.
- Monitor animals closely for signs of respiratory distress.
- Check feed and water sources for contamination from ash or smoke residues.
- Review emergency plans in case wildfire conditions worsen or transportation routes become restricted.
Keeping Farmers Safe
Farmers, and those who wok on the farm, often spend long hours outdoors, increasing their exposure to smoke and elevated fine-particle pollution.
Public Health Ontario notes that wildfire smoke contains fine particulate matter (PM2.5), which can penetrate deep into the lungs and contribute to respiratory and cardiovascular effects. Symptoms may include coughing, throat irritation, headaches, shortness of breath, and eye irritation.
During smoky conditions, farmers should:
- Monitor the Air Quality Health Index (AQHI) throughout the day.
- Reschedule strenuous outdoor work when air quality is poorest.
- Increase rest breaks for field crews.
- Ensure workers stay hydrated.
- Provide access to enclosed, filtered-air environments whenever possible.
- Consider appropriate respiratory protection when conditions warrant and occupational safety requirements are met.
When will smoke conditions improve?
At the moment, the outlook varies across Ontario.
- Southwestern Ontario (London, Sarnia, Windsor) may wait longer. Current forecasts suggest the thickest smoke plume is shifting southward, and air quality could remain poor into Friday, with some uncertainty extending into the weekend.
- Eastern Ontario (Ottawa Valley, Kingston, Peterborough) is expected to see gradual improvement beginning late today and into this evening as winds shift.
- Northern Ontario will likely continue experiencing smoke impacts as long as major fires remain active. Forecast rain may provide some relief but is not expected to extinguish the fires or fully eliminate smoke.
Weather forecasters note that northwesterly winds may continue transporting smoke into parts of Ontario through the weekend while large wildfires remain active.
Most of southern Ontario should begin seeing some improvement between tonight and Friday, but a complete return to clear conditions is not yet guaranteed because there are still more than 100 active fires burning in Ontario and changing winds could bring additional smoke south.
Stay safe!