BROOKINGS, S.D. (AP) - Farmers in the Northern Plains often worry about what the weather could do to their crops - but they seldom think about what their crops could do to the weather.

A new NASA-funded study at South Dakota State University will tackle that question by asking whether regional weather patterns and the risk of wildfires could change because of a shift in planting. Farmers may grow fewer corn and soybean crops and more perennial grasses grown primarily to fuel cars.

Scientists at the university's Geographic Information Science Center of Excellence and their collaborators will look at the potential effects of such a shift in South Dakota, North Dakota, Nebraska, western Minnesota and northern Iowa under different scenarios, said Geoff Henebry, an SDSU professor and senior scientist at the center.

Many factors can change the seasonal cycle of exchanges of water and energy between the land and the lower portion of the atmosphere, Henebry said.

For instance, perennial grasses use more water early in their growing season than corn or soybean plants.

"As you change the land surfaces, you change the characteristics of the seasonality of the vegetation growth and water use and the brightness," he said.

Senior scientist Michael Wimberly said the researchers are not trying to predict exactly what will happen. Their goal is to make some broad but reasonable assumptions so potential consequences can become part of the discussion.

The $738,000 study is timely because it involves feedstocks such as switchgrass that are used for biofuel - which is expected to be more widely used in future ethanol production. Most domestic ethanol now comes from corn.

One concern is that a move toward widespread use of switchgrass and other perennial grasses could increase the potential of wildfires.

Dried-out grasses are a hot fuel source, and farm machinery could easily provide a spark for ignition. That could become a problem in a region known for its relatively high sustained winds, and many fire departments don't have experience in large grass fires, Henebry said.

"Switchgrass is highly flammable, and grass fires are really fast and furious," he said.

Such fires were common in the tall grass prairie thousands of years before European settlement.

"You look at historical records and that's one of the first things people would do after homesteading is you get some kind of a fire break around your property," Henebry said.

Agricultural use of fire continues, but it tends to be localized in grazing land.

Wimberly said research could lead to the development of practices to decrease such risks.

"If the hazards are recognized and understood, then there's a good chance they can be managed and mitigated," Wimberly said. "So the idea is to get out ahead of the curve and try to envision some of these things rather than being in a reactive mode somewhere down the line after they become a problem."