GRAND FORKS, N.D. (AP) -- Corn planting is swinging into high gear in the upper Midwest, and some farmers are finding it a challenge to get enough of the seed they want.

"It's short, particularly (biotech) corn," Neal Foster, executive director of the South Dakota Crop Improvement Association, told Agweek (http://bit.ly/HPKtcx ).

The reason is largly that farmers nationwide are planting what is expected to be one of the biggest corn crops in decades. U.S. Department of Agriculture estimates peg the crop at nearly 96 million acres, up 4 percent from last year and the highest level since 97.2 million acres in 1937. Seed supplies also are crimped by wet weather last year that led to less corn seed being planted, and, ultimately harvested.

Corn is used for everything from human and livestock food to ethanol fuel.

Corn acreage is expected to increase by about 14 percent, total, in the Dakotas and Minnesota, according to federal estimates. In North Dakota, the increase is projected to surpass 50 percent, to 3.4 million acres, although some farmers have said the tight seed supplies might lower that figure.

Adam Spelhaug at Peterson Farms Seed in Harwood said he thinks acreage in the state still will top 3 million acres, although he is skeptical if the USDA projection will be reached.

Minnesota Department of Agriculture spokesman Steve Malone said some corn farmers might be forced to grow a variety that is not their first choice.

"If you want to plant corn, you'll be able to find seed. It may not be what you want," he said.

USDA estimates are 3.4 million acres of corn in North Dakota, up from 2.2 million acres last year; 8.7 million acres in Minnesota, up from 8.1 million; and 5.5 million acres in South Dakota, up from 5.2 million.

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Information from: Grand Forks Agweek, http://www.grandforks.com/mld/agweek/

Copyright 2012 The AP.