Corn offers fell 3 to 4 cents per bushel, weighed by declines in the CIF market, which supplies grain export terminals at the Gulf Coast.
Traders were seeing little export demand ahead of year-end holidays. At the same time, more corn was available from farmer selling last week during a Chicago Board of Trade rally.
Lower barge freight on interior rivers leading to the Gulf Coast also pressured CIF values.
On the Illinois River, barges were bid at 450 percent of tariff, down from 475 percent on Friday. Bids on the Mississippi River at St. Louis were 410 percent, down from 420 percent.
Barges on the lower Ohio River traded at 400 to 415 percent, compared with 425 percent last week.
Warmer temperatures in the Midwest alleviated concerns about icy river conditions hampering barge movement that had driven freight higher, a barge operator said. But grain movement to the Gulf Coast from recent farmer selling will limit how much further freight can fall.
Soybean offers were down about a penny per bushel, also pressured by a drop in the CIF market. Traders said it was unlikely that China would buy more US soyabeans before the end of the year.