DECATUR, Ill. — Agribusiness giant Archer Daniels Midland Co. (ADM) will trim nearly one in five jobs at its corporate headquarters in Illinois, citing uncertainty in grain markets overseas as the primary reason.

CEO Patricia Woertz said in a prepared statement 1,000 jobs will be eliminated, but first through early retirement offers to those at least 57 years old and who meet other requirements.

ADM employs approximately 30,000 people and operates more than 270 plants worldwide. “To ensure that we can continue to compete effectively in our global markets, we are taking actions to streamline our organization and achieve significant, sustained cost reductions,” Woertz said. “These actions will help us enhance our productivity and savings power.”

The reductions will focus on corporate staff as a way to decrease overhead and not change operations, said ADM spokesman David Weintraub. Most of the corporate jobs in question are based in Decatur, leaving the area in a vulnerable spot, said Craig Coil, president of the Economic Development Corp. of Decatur and Macon County.

“It’s kind of a bitter pill to swallow in that regard. It’s one of those things we can’t control,” Coil said. “We’ll automatically feel a disproportionate impact of that because of the fact we’re a fairly small community and they’re a major player in our community.”

Despite the plan to cut positions, Coil said ADM is committed to the Decatur area, and the reductions should not reflect negatively on Decatur itself.

“We know the commitment is there for those production positions. They’re following suit with a lot of the other companies around the globe who are looking at ways to improve profits and, at the end of the day, improve stock prices and their bottom line,” he said.

One such rival making cuts as well is Minnesota-based Cargill, Inc., which announced plans last month to cut 2,000 jobs, about 1.5 percent of its worldwide workforce of about 130,000 people.

ADM reported $2.03 billion in profits for the last fiscal year, but crop markets historically make for unpredictable revenue. Corn and soybean prices were volatile last year, hitting near-record levels, then plunging in a matter of months.

“This past year, we’ve seen corn prices vary by more than $2 a bushel,” said Darrel Good, an ag economist with the University of Illinois extension. “That kind of variation continues. Since mid-December, we’ve seen almost a dollar swing in prices.”

Weintraub said employees will have until early next month to decide whether to take the retirement package. Workers can start to retire after Feb. 29, with the process continuing until February 2013, he said.