Another potential benefit to crops is that increased airflows could enable corn and soybean plants to more readily extract CO2, a needed fuel for crops, from the atmosphere and the soil, thus helping the crops' ability to perform photosynthesis. Takle's wind turbine predictions are based on years of research on so-called agricultural shelter belts, which are 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," said Takle. "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's initial measurements consisted of visual observations of wind turbulence upwind and downwind of the turbines. The team also used wind-measuring instruments called anemometers to determine the intensity of the turbulence. The bulk of the wind-turbulence measurements and the crop-moisture, temperature and CO2 measurements took place in the spring and summer of this year.

"We anticipate the impact of wind turbines to be subtle, but in certain years and under certain circumstances the effects could be significant," said Takle. "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." The CU-Boulder and ISU teams hope to continue their measurements throughout the next growing season.

"These data are quite encouraging, and we look forward to collecting more data to ensure the certainty of these results," said Lundquist. "As wind energy expands in future years to provide a domestic source of energy, we'll need robust measurements to understand and predict the impacts of that expansion."

The research was funded or supported by Ames Laboratory, the Department of Energy's Office of Energy Efficiency and Renewable Energy, the U.S. National Laboratory for Agriculture and the Environment, CU-Boulder and NREL.

To view a video of Takle discussing the study of wind turbines on farmland visit www.youtube.com/watch?v=r7qNNvYVKI4&feature=player_embedded