As Michigan's summer crops continue to grow, residents may notice a familiar smell on warm summer evenings: corn.
The scent often raises questions about whether the state's vast corn fields are making already hot and humid conditions even more uncomfortable.
While corn does release large amounts of water into the air, experts say the process is a natural part of how plants survive during the summer.
The process is called evapotranspiration but is know by many as "corn sweat." Caleb Ivins with Michigan Storm Chasers says it happens when corn plants absorb water from the soil and release it through their leaves into the atmosphere.
"Think of it kind of like how when we get warm and we sweat," Ivins said. "We transpire on our skin, we get kind of sweaty. The corn plants do the same thing when they're stressed during the day or when it's really hot. They'll release that water to help cool the plant off and limit stress on the plant."
While corn is not the only plant that goes through evapotranspiration, Ivins said it is especially efficient at the process.
An acre of corn can release between 3,500 and 8,000 gallons of water per day during peak growing season. The highest amount of water loss happens when corn reaches the tasseling stage, when the plant stops focusing on growing leaves and begins putting energy toward producing ears and forming kernels.
Ivins said this peak period usually occurs from mid- to late July.
"That's when the corn plant is switching gears internally," Ivins said. "It's no longer focusing its time and energy on vegetative growth. It's now wanting to spend its energy on reproduction, focusing all of its energy on the ear of corn that it's developing."
Despite the amount of moisture corn releases, Ivins said it has little effect on overall humidity levels because there is already a large amount of moisture in the summer atmosphere.
"When you really think about how much volume of moisture is already in the air this time of year, it makes the cornfield kind of like adding a drop of water into a bathtub," Ivins said.
The process can still be noticeable at night. After the sun goes down, the ground and air near corn fields begin cooling. The moisture released from the plants can then condense, creating shallow patches of fog over fields and low-lying areas. That fog is also what can carry the familiar smell of corn on calm summer evenings.
Ivins said the smell is often strongest when conditions are calm and warm air traps a layer of cooler air, allowing moisture from the fields to remain near the surface.
The recent late June and early July heat wave also affected how much moisture corn was releasing. Ivins said much of Michigan's corn had not yet reached its peak growth stage, meaning the plants were not releasing the maximum amount of water.
During periods of extreme heat, plants can actually reduce evapotranspiration as a defense mechanism. When temperatures rise above about 85 degrees and the plant begins losing more water than it can replace, corn will conserve moisture. Leaves may curl during the hottest part of the day before relaxing again overnight.
Ivins said evapotranspiration is ultimately a cooling system for plants.
"It's kind of a natural air conditioner," Ivins said. "The moisture rises off your skin, it cools, it condenses, and it sinks back down. That same process is replicated in plants just as it is on our skin as well."
Although corn often gets blamed for summer humidity, Ivins said larger weather patterns have a much bigger influence. Strong high-pressure systems common in the summer can trap warm, moist air near the surface, creating the hot and humid conditions Michigan experiences during heat waves.
He added that corn is only one part of a much larger system. Trees, soybeans and other vegetation also release moisture into the atmosphere during the growing season.
For Ivins, the biggest takeaway is that corn is not creating Michigan's summer heat. Instead, the crop is responding to those conditions by using evapotranspiration as a way to cool itself.
"When we're hot and sweaty, that corn's feeling it all the same as we are," Ivins said.
This story is brought to you as part of a partnership between WKAR and Michigan State University's Knight Center for Environmental Journalism.