Chicago wheat fell again Monday, remaining close to Friday's five-week lows, as Türkiye's ban on imports triggered worries about reduced demand and intensified competition with Black Sea supplies in export markets.
Corn rose after Friday's losses, while soybeans fell.
The Chicago Board of Trade's (CBOT) most-active wheat Wv1 fell 0.4% to $6.24 per half a bushel at 9:25 a.m. GMT.
Wheat on Friday hit its lowest since May 6 at $6.18 a bushel after Türkiye said it would halt wheat imports from June 21 to at least Oct. 15 to protect farmers, ensure domestic procurement of raw materials and create a favorable market for producers.
Türkiye is the world's fifth largest wheat importer, buying mostly from Russia.
Corn Cv1 rose 0.2% to $4.49 per three-fourths a bushel. Soybeans Sv1 rose 0.02% to $11.79 per half a bushel.
"Wheat is still being weakened today by the news of Türkiye's import ban," said Matt Ammermann, StoneX commodity risk manager.
"This would mean that Black Sea wheat, especially Russian, which would have gone to Türkiye, may now be sold elsewhere in competition to U.S. and other exporters."
"The market seems to be tired of reports about weather damage to Russian crops and is seeking other factors to trade."
There was additional pressure on wheat stemming from expectations of a bumper U.S. winter harvest, which have eased worries arising from Russian crop damage.
Russia said on Friday it was declaring a federal emergency in 10 regions because of damage to crops from May frosts, a measure that will help farmers with extra funds but which officials said should not derail export obligations.
Corn and soybeans were drifting as the week starts, ahead of news later this week from U.S. Department of Agriculture (USDA) crop reports on Wednesday and the U.S. Federal Reserve (Fed) policy meeting.
Analysts in a Reuters poll estimated the USDA's June 12 crop production report would forecast a harvest of 1.298 billion bushels of U.S. winter wheat, above the May estimate.
"Corn is seeing some buying interest after Friday's fall. Overall, U.S. Midwest weather is looking positive, and the strong U.S. dollar is weakening soybeans," Ammermann said.
China imported 10.22 million metric tons of soybeans in May, customs data showed on Friday, below the levels of a year ago but more than April's shipment volumes, as good crush margins supported demand for cheaper Brazilian beans.
Large speculators increased their net short position in CBOT corn futures in the week to June 4, regulatory data released on Friday showed.
The Commodity Futures Trading Commission's (CFTC) weekly commitments of traders report also showed that noncommercial traders, a category that includes hedge funds, trimmed their net short position in CBOT wheat and increased their net short position in soybeans.