Barge freight was lower on the lower Mississippi River at St. Louis and steady-lower on the Illinois as harvest neared completion. Rates were firm on the lower Ohio River.
Traders said corn basis values were firm, supported by slow farmer selling, but export demand was sluggish.
"Demand seems to have quieted down today," a trader said, adding that importers were likely holding out for the USDA's corn and soya crop production reports on Thursday.
Traders were also watching out for developments in the outbreak of bird flu, especially in Asia where China has culled 6 million poultry in the country's north-eastern region.
A trader said the spread of bird flu in China could lead to the country exporting more corn as domestic feed consumption falls due to the disease.
China competes with the United States in the global corn export market, but the country has been expected to cut back on shipments as its domestic consumption grows, traders said.
Traders said hard and soft red winter wheat basis offers were mostly steady, supported by slow farmer selling.
The traders said lower rail freight rates were keeping the pressure on HRW wheat basis values in the track market.