COLUMBIA, Ill. — His face smudged with dark grit, Glen Mueller stepped down from a mammoth combine this week and stared out across a corn crop jeopardized by quandaries far larger than the machinery towering over him.

He and other farmers are facing a double whammy as the harvest begins. The record yields of last year are a faded memory, replaced by crops parched, browned and thinned by months of drought. And now, damage done by Hurricane Katrina threatens to push up the cost and create delays in getting this year's crop to export terminals down the Mississippi River.

"It's going to be a rough year," says Mueller, his clothes covered with a fine dust of pulverized corn husks and stalks. "I just hope to make enough to be here next year."

Even as the river reopens to shipping, the snarled barge traffic caused by Katrina continues to threaten the ability of Mueller and other farmers to get their grain to overseas markets. Many farm cooperatives and grain elevators say they have little, if any, storage space for farmers who still haven't even hit the stride of their harvests.

That will likely force farmers to store grain on their own in hopes of getting a better price later. But it will be a difficult balance. Mueller says he will have to sell some now at cut-rate costs to get rid of it before it rots.

The troubles of Mueller, who farms nearly 600 acres about 15 miles from St. Louis, highlight American agriculture's dependence on river shipping that has long been the cheapest, most efficient means of moving commodities to overseas consumers.

The United States exports a quarter of its grain. More than half of what's exported departs from Gulf ports pounded by Katrina. Grain-carrying ships are slowly moving again through those ports, but problems remain.

For example, at agribusiness giant Bunge Limited's export terminal in Destrehan, La. — which normally handles a million bushels a day for shipment to Central America and Europe — operations remain slow. The problem is a lack of available barges that can head north, retrieve grain from Midwest farmers and bring it south to Gulf ports, spokeswoman Debra Seidel said.

"Progress is being made, but it's not near normal yet," she said.

The river disruption is rippling through the farming economy. Midwest co-ops and grain elevators looking to clear out stored corn from last year — about 2 billion bushels, according to the National Corn Growers Association — say they're having a tough time doing so because, among other things, barges are getting snarled down south.