A multiyear study led by an Iowa State University scientist suggests wind turbines in operation in the state may be having a positive effect on crops.
Gene Takle, a professor of agronomy and geological and atmospheric sciences, says wind turbines disbursed throughout a field create air turbulence that may help plants by affecting variables such as temperature and carbon-dioxide concentrations.
Takle and his team installed research towers on a 200-turbine wind farm between Radcliffe and Colo. The research towers collected data from 2010 to 2013 on wind speeds and directions, temperature, humidity, turbulence, gas content, and precipitation. The project aimed to discover how the turbulence created when wind moves through the turbines affects conditions at ground level where crops grow.
Takle says the team’s data show that the turbines have a measurable impact on several key variables that affect growing conditions. It’s more difficult to pin down whether those changes affect crop performance, but Takle says wind turbines may make growing conditions more favorable for corn and soybeans.
“On balance, it seems turbines have a small, positive impact on crops,” he explains.
In addition, he says turbines can change the temperature in the areas around them. The research team’s data show that turbulence produced by wind turbines leads to temperatures about a half degree cooler during the day and between a half to a full degree warmer at night.
According to Iowa State, that’s because the turbulence mixes air at different elevations: The mixing cools the ground level during the daylight hours in the way that a fan blows on a wet surface. But at night, as the ground loses heat, the mixing brings warmer air aloft down to ground level – resulting in a net warming effect.
The turbulence also suppresses the formation of dew and dries the crops – which 
could combat harmful molds and fungi, Takle says.
The turbulence and the associated changes in air pressure at ground level also may enrich the carbon-dioxide content in the air surrounding crops – making the plants grow more efficiently, according to Takle.
He says the researchers set out to determine if wind turbines impact the factors that influence growing conditions in a field. The answer appears to be yes, but he notes that figuring out if those changes actually improve plant performance poses a bigger challenge.
“The next step would be to answer if this turbulence changes biomass uptake of plants or if it affects plant size or functions or yield,” he says. “It’s going to be much harder to find those answers because of all the other factors at play in a field, such as variations in soil quality or precipitation.”
The research was supported by a $1.3 million grant from the National Science Foundation, says Iowa State.
