CHICAGO — The Russian invasion of Crimea in Ukraine has put world grain markets on notice that there may be rough sledding, especially for wheat and corn futures, as traders attempt to assess the effects of the political crisis.

Following a surge in prices in European markets, hard and soft winter wheat prices soared in early futures trading at the CME Group’s Chicago Board of Trade, as did hard spring wheat futures prices at the Minneapolis Grain Exchange on March 3, following strong gains in those markets on Feb. 28.

Mid-morning Monday, Chicago March soft red winter wheat was up 34½c at $6.35 a bu and headed to more than 40c higher before slipping back a few cents. The upward surge carried prices up about 7%, the largest gain in more than 20 months. March corn futures were trading at $4.68¼ a bu, up 10¾c.

The futures market was attempting to put a value on the effect of possible disruptions in trade from the current turmoil in the Black Sea region. There were questions about how the Russian occupation of Crimea may affect prices and availability of Ukrainian corn and wheat exports still to be delivered in the current 2013-14 crop year, which ends May 31 for wheat and Aug. 31 for corn.

The U.S. Department of Agriculture projected Ukraine will export a record 10,000,000 tonnes of wheat in 2013-14, on production of 22,278,000 tonnes, slightly less than the record 22,324,000 tonnes produced in 2011-12.

The U.S.D.A. also projected Ukraine will export a record 18,500,000 tonnes of corn in the current crop year out of total production forecast at 30,900,000 tonnes.

Sid Love, a grain analyst in Overland Park, Kas., said that uncertainty tends to produce higher prices in grain markets.

“There’s an old saying — when in doubt, get out,” Mr. Love said. The many unknowns brought by the Russian military move against Ukraine triggered widespread short-covering, especially by commodity funds, he said.

Dow Jones Newswires reported Ukraine had exported 7,400,000 tonnes of wheat (6,100,000 tonnes was milling wheat) and nearly 15,000,000 tonnes of corn so far in this crop year. Barley accounted for the remaining 2,150,000 tonnes so far this year.

Market observers said at least several million tonnes of already-sold corn and wheat were languishing in Ukraine, awaiting shipment amid worries that Ukraine’s currency may collapse.

Stateside, shares of U.S. grain companies such as Archer Daniels Midland and Bunge, both of which do significant business in the Black Sea region, took a hit, falling 1.8% and 1.6%, respectively, by mid-morning Mar. 3, newswires reported.