Corn futures in Chicago fell the most in almost three weeks on Wednesday as profit-taking hit the grain market following a weekslong rally. The most-active contract dropped as much as 1.8% during intraday trading, its biggest decline since August 13. The pullback in corn came after prices were driven higher by supply concerns, including escalating attacks on Black Sea ports and ships, as well as global heat waves threatening crop output.

Wheat and soybeans also retreated amid the broader commodity sell-off. The losses highlight the volatility in grain markets as traders react to shifting geopolitical and weather-related risks.