GRUNDY CENTER -- Call it luck. Call it fate. Call it whatever you want. Mark Buskohl and other Grundy County farmers are just glad they raise crops in some of the most fertile soil in the world.

Geological changes thousands of years ago, combined with flat ground and favorable weather conditions, make Grundy County the garden spot of Iowa. While the county's farmland may not always produce the top yields in the state, soil experts agree it is the best.

"We farm in Tama County and bought into a farm in Missouri. There's no comparison (to Grundy County)," said Buskohl, a fourth generation grain and livestock producer who primarily farms northeast of Grundy Center. "We're fortunate we're here."

The debate concerning which region has the best farmland has raged for years. A recent Associated Press story quoted an Illinois soil scientist bragging up his state saying, "God didn't make many places as good as this."

Iowa's soil experts say it's virtually impossible to pinpoint the most fertile place on earth. Spots in Illinois, the Ukraine, Argentina and along the Yellow River in China can stake their claim.

When it comes to Iowa, however, Grundy County is at the top of the food chain. The latest corn suitability ratings -- a measure of farmland productivity by judging factors such as soil fertility, weather patterns and topography -- compiled by Iowa State University proves it.

On a scale of zero to 100, with 100 being the best, Grundy averages 84.7. The nearest competitor, Mitchell County, rates seven points less.

Gerald Miller, an ISU agronomist and soil expert, helped update the CSR ratings last year. He said no other county can match Grundy's combination of organic matter in the soil, favorable weather patterns -- especially rainfall -- and flat terrain. For example, parts of western Iowa have fertile soil, but lack the rainfall of Grundy County by several inches.

"You (Grundy County farmers) have everything going for you. … It's the garden spot," Miller said.

Soil experts said as the earth evolved and Northeast Iowa's valuable top and subsoil were created, Grundy County just happened to be in the right spot at the right time.

At one time, Northeast Iowa was densely forested, experts said. About 25,000 years ago, glaciers moved in, essentially compacting everything underneath a quarter-mile of ice. Jerry Hatfield, director of the National Soil Tilth Laboratory in Ames, said tree trunks have been found 20 feet deep. This helped create a deep, subsoil profile.

When the glaciers disappeared 12,000 years ago, the area's soil was essentially 13,000 years younger than other farm ground, making it more productive by default. Native prairie grasses then covered the region. As the prairies continually regenerated, the dying plants morphed into more fertile soil.

Dust storms were also common, dumping mineral-rich river basin soil in the Cedar Valley. In most parts of Grundy County, just the right combination of organic matter, sand, silt and clay were deposited.

The soil contains 7 percent organic matter in many areas, Miller said, compared to 3 percent or less in other parts of the state. It also has an uncanny knack of retaining moisture and promoting a healthy gas exchange. When crops in western Iowa, for example, are withering due to a lack of water, most Grundy County fields fight off drought two or three weeks longer.

"What makes the soil so good are the microbes (breaking down organic matter into nutrients), earthworms (less compaction) and the ability to hold water. It's just head and shoulders above everywhere else," Hatfield said.

"I would say it's among the richest farmland in the world," he added.

Corn yields in Grundy County last year averaged 190.6 bushels per acre. Soybeans averaged 54.2 bushels. Both were tops in Northeast Iowa.

"I've never averaged 200 bushels per acre (corn) before. I did it last year," Buskohl said.

As long as farmers are good stewards of the land, Miller said there's no reason the high level of productivity can't be maintained for another 3,000 years. Essentially, Iowa has only been farmed for 160 years, he said.

Bill Myers has farmed near Beaman for about 50 years. He knows how fortunate he is, and he plans to keep the land healthy.

Myers has incorporated many conservation tillage practices: No-till and minimum till -- not exposing precious topsoil to the elements -- and building grass waterways and terraces where needed.

"We've got some of the best black dirt going. If you take care of the land, it will take care of you," Myers said.

While farmers are grateful for the productive soil, the lofty CSR ranking also has drawbacks. It means the 324,129 acres is some of the most expensive in the state, averaging $3,493 per acre in 2004, a 12.6 percent increase from 2003.

Buskohl, who has two sons in college, would love one of them to return to the county and farm. But joining the family operation means more income is needed, and most likely that means a need for more land.

Renting land isn't exactly cheap either, he said. In 2004, the average cash rent was $139 per acre, though some pay much more.

"It's very competitive (buying or renting land)," Buskohl said. "It's very hard to establish the next generation.

Matthew Wilde can be reached at (319) 291-1579 or matt.wilde@wcfcourier.com.