Record July heat raises concerns over corn growth and grain fill
Record-breaking heat across much of the United States is raising concerns about potential impacts on corn production. Researchers say that while daytime temperatures often get the most attention, high nighttime temperatures can also play a significant role in reducing yield.
Studies show that overnight temperatures above 70°F can negatively affect corn plants, especially during key growth stages. The most sensitive period occurs around silking when kernel numbers are being determined. Stress during this stage can reduce kernel formation and limit the crop's yield potential.
“Unlike photosynthesis – which only happens during the day – respiration keeps running all the time,” said Mark Jeschke, Pioneer agronomy manager. “It’s a temperature-dependent reaction, so the warmer it is, the faster it goes. When the nighttime temperature increases, the total expenditure of energy through respiration also increases, leaving less energy to contribute to grain fill.”
Warm nights increase the rate of plant respiration, a natural process that continues around the clock. As temperatures rise, corn plants use more energy for maintenance and survival, leaving less energy available for grain development. This can result in lighter kernels and reduced overall productivity.
Extended periods of high nighttime temperatures may also speed up the crop's development. Corn accumulates growing degree units as temperatures remain within favorable ranges, causing plants to mature faster. While quicker maturity may sound beneficial, it can shorten the grain fill period, reducing the time kernels must gain weight.
Researchers suggest that prolonged exposure to warm nights can reduce yields by 15% or more in some situations. Additional effects may include increased water stress, faster leaf aging, reduced photosynthesis, and lower pollen viability.
Although extreme heat is often associated with pollination problems, studies indicate that heat-related pollination failure is relatively uncommon in North America. Instead, yield losses are more frequently linked to the crop's physiological response to sustained heat stress.
Research also shows that corn hybrids vary in their ability to tolerate high nighttime temperatures. Some hybrids experience significant yield declines, while others perform considerably better under similar conditions. This variation highlights the importance of hybrid selection as growers adapt to changing weather patterns.
As summers continue to bring warmer nights, understanding heat stress and choosing resilient hybrids may become increasingly important for protecting corn yields and maintaining profitability.
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