U.S. corn futures fell on Monday due to waning demand from ethanol producers and exporters, traders said.
Soybeans, which have provided support to the entire grain complex over the last few weeks, were mixed, with the benchmark January contract bucking the overall downward trend due to tight supplies.
"Strong U.S. demand continuing into the holidays and into the first quarter of 2013," brokerage INTL FCStone said in a research note to clients. "It is no surprise that the front month is outrunning all the deferreds."
Wheat futures dropped as a wave of technical selling hit the market. The benchmark March contract closed below its 200-day moving average for the first time since June.
Corn prices have fallen for seven of the last eight trading days as supply concerns have eased amid the slowdown in demand. Chicago Board of Trade (CBOT) March corn settled down 6-3/4 cents at $7.24 a bushel (all figures US$).
"You continue to see slow exports and ethanol profitability remains dismal," said Al Kluis, president of Kluis Commodities.
CBOT January soybeans were 1/4 cent higher at $14.96-1/4 a bushel while CBOT March soybeans closed down 3-1/4 cents at $14.88-1/4. The front-month contract hit a 5-1/2-week high early in the session but scaled back its gains as deferred months turned lower.
CBOT March wheat ended off six cents at $8.08 a bushel.
The declines in soybeans were limited by forecasts for low U.S. stockpiles and worries about South American supplies.
Soybeans had gained 1.3 per cent on Friday after data from the National Oilseed Processors Association showed U.S. soybean processors crushed 157.308 million bushels in November, the largest for the month since November 2009, and the biggest overall since January 2010.
Processors are crushing at a high rate to meet the strongest demand for U.S. soybean meal since the record year of export sales in the 2009-10 marketing season, industry sources said.
Export demand for soybeans has also been strong, especially from top global soy buyer China, which has forced domestic processors to bid up for soybean supplies.
Widespread rainfall moved across Argentina over the weekend causing another slowdown in crop seedings and the rain is expected to continue through Wednesday, said John Dee, meteorologist for Global Weather Monitoring.
"This rain certainly isn't welcome but they did have 10 to 14 days of drier weather leading up to it so they were able to get some work done," Dee said.
Argentina's soybean harvest has been pegged at 53 million tonnes by the Rosario grains exchange.
"The overly wet weather, in other words, is having a greater impact on expectations in the country itself," Commerzbank said.
-- Mark Weinraub covers the grain futures markets for Reuters in Chicago. Additional reporting for Reuters by Sybille de La Hamaide in Paris and Colin Packham in Sydney.