By DOUG SCHMITZ
Iowa Correspondent

SAN FRANCISCO, Calif. — Researchers at the U.S. Department of Energy’s (DOE) Ames Laboratory at Iowa State University and the University of Colorado-Boulder might have found evidence that wind turbines increasingly peppering the Midwest farmland provide beneficial breezes to nearby corn and soybeans.

“We’ve finished the first phase of our research, and we’re confident that wind turbines do produce measureable effects on the microclimate near crops,” said Gene Takle, Ames Laboratory associate and an ISU professor of agricultural meteorology, at the American Geophysical Union’s annual meeting last December in San Francisco.

Takle and co-researcher Julie Lundquist, assistant professor at UCB’s Department of Atmospheric and Oceanic Sciences and joint appointee at the DOE’s National Renewable Energy Laboratory, announced their preliminary findings.

Funded by the Ames Laboratory’s royalty income seed funding program, which supported the initial work, the study’s additional funding came from the DOE’s Office of Energy Efficiency and Renewable Energy. The U.S. National Laboratory for Agriculture and the Environment contributed the surface flux instruments used to measure the turbines’ effects, and the personnel to operate them.
In a months-long research program aimed at studying how wind turbines on farmlands interact with surrounding crops, the researchers said the giant blades that generate renewable energy might also help corn and soybean crops “stay cooler and dryer, help them fend off fungal infestations and improve their ability to extract growth-enhancing carbon dioxide from the air and soil,” while “bathing the crops below, via the increased airflow they create.”

Lundquist and her research team have been using a specialized laser known as a lidar to measure winds and turbulence from near the Earth’s surface to well above the top tip of a turbine blade to “detect a beautiful plume of increased turbulence” that persisted 250 feet high and a quarter-mile downwind.
Takle and Lundquist’s initial measurements consisted of visual observations of wind turbulence upwind and downwind of the turbines. They said their early findings, however, have yet to “definitively establish whether or not wind turbines are in fact beneficial to the health and yield potential of soybeans and corn planted nearby,” although preliminary results that the turbines increase airflow over surrounding crops may suggest “a realistic possibility.”

“The turbulence resulting from wind turbines may speed up natural exchange processes between crop plants and the lower atmosphere,” said Takle, who collected data last summer from Midwest fields surrounding turbines, where he also collected wind fluctuations, temperature changes and carbon dioxide from fields adjacent to them.

He said crops warm up when the sun shines on them, and some of that heat is given off to the atmosphere.

“Extra air turbulence likely speeds up this heat exchange, so crops stay slightly cooler during hot days,” he said. “On cold nights, turbulence stirs the lower atmosphere and keeps nighttime temperatures around the crops warmer.
“In this case, we anticipate turbines’ effects are good in the spring and fall because they would keep the crop a little warmer and help prevent a frost. Wind turbines could possibly ward off early fall frosts and extend the growing season.”

Takle said other benefits of turbines could result from effects on crop moisture levels. “Extra turbulence may help dry the dew that settles on plants beginning in late afternoon, minimizing the amount of time fungi and toxins can grow on plant leaves,” he said. “Additionally, drier crops at harvest help farmers reduce the cost of artificially drying corn or soybeans.”

Still, another potential benefit is increased airflows enabling corn and soybean plants to more readily extract much-needed atmospheric carbon dioxide.
“The extra turbulence might also pump extra carbon dioxide from the soil,” he said. “Both results could facilitate the crops’ ability to perform photosynthesis.”
Takle based his wind turbine predictions on years of research on agricultural shelter belts, which are the rows of trees in a field designed to slow high-speed natural winds.

“In a simplistic sense, a wind turbine is nothing more than a tall tree with a well-pruned stem,” he said. “For a starting point for this research, we adapted a computational fluid model that we use to understand trees. But we plan to develop a new model specific to wind turbines as we gather more data.”
The team also used wind-measuring instruments called anemometers to determine the intensity of the turbulence, with the bulk of the turbulence and crop-moisture, temperature and carbon dioxide measurements gathered last spring.

“We anticipate the impact of wind turbines to be subtle,” he said. “But in certain years and under certain circumstances, the effects could be significant.
“When you think about a summer with a string of 105-degree days, extra wind turbulence from wind turbines might be helpful. If turbines can bring the temperature down below 100 degrees, that could be a big help for crops.”

While Takle and Lundquist’s research is continuing, he said additional study is needed to gather more information from the different types of weather, as well as data from the earlier and later parts of the growing season.