Corn was little changed as the market awaited a clearer picture of harvest yields.
Investors turned attention towards grain stocks data to be published next Monday by the US Department of Agriculture (USDA).
Chicago wheat ticked lower, with traders watching a tender by Egypt for an update on international competition, while Minneapolis spring wheat stayed firm with support from a rain-affected harvest in the northern United States.
The most-active soybean contract on the Chicago Board Of Trade was down 0.2pc at $8.92-1/4 a bushel as of 1102 GMT, while CBOT corn added 0.3pc to $3.75-3/4 a bushel.
CBOT wheat eased 0.4pc to $4.80 a bushel, but MGEX spring wheat futures edged up 0.6pc to $5.47-1/2 to stay close to a near three-month high struck on Tuesday.
"Grain markets were mixed again overnight as traders continue to watch for signs of demand from China in the form of overnight export sales, while at the same time looking to estimates for next Monday's USDA reports," brokerage Allendale said in a note.
China has made large purchases of US soybeans this month in what has been viewed as part of goodwill gestures to help discussions in the year-old US-Chinese trade dispute.
China has awarded new waivers to importers to US soybeans free from tariffs imposed during the trade war, two sources familiar with the matter said on Tuesday, raising expectations of further purchases.
Large export sales of US crops are declared to the USDA under a daily reporting system, providing potential confirmation of Chinese buying.
However, Trump's condemnation of Chinese trade policy in his address at the United Nations on Tuesday cooled recent hopes of progress towards resolving the dispute.
"Chinese buying is supporting the market although it is just a short-term support as concerns remain about the trade war," said Phin Ziebell, agribusiness economist at National Australia Bank.
In the wheat market, the focus is on a tender set by Egypt, the world's top importer, to buy wheat for shipment from Oct. 26 to Nov. 5.
The tender will indicate whether competition remains stiff after large northern hemisphere harvests and brisk early-season sales by Black Sea exporters, such as Ukraine.