Corn followed soybeans higher and drew further support from bullish weekly US ethanol data, and wheat snapped out of a four-session slide.
At the Chicago Board of Trade, soybeans for January delivery settled up 23-3/4 cents, or 1.6 percent, at $14.79-1/4 per bushel after reaching $14.79-3/4, the contract's highest level since Nov. 9.
CBOT March corn ended up 5-3/4 cents, 0.8 percent, at $7.57-3/4 a bushel, and March wheat rose 3-1/2 cents, 0.4 percent, to end at $8.60 a bushel.
CBOT January soybeans made a solid break above their 200-day moving average at $14.64 and settled above that line for the first time in nearly a month.
Wednesday's soy market strength followed a late-session rally on Tuesday as rumors swirled of renewed Chinese demand for US soybeans, sourced from exporters in the Pacific Northwest.
"There has been talk that China has bought maybe up to six cargoes this week," said Ken Smithmier, grains analyst at the Hightower Report in Chicago.
Exporters have been competing for soybeans on the cash market with domestic processors, which are currently reaping high profit margins from crushing raw soybeans into soymeal, a key source of protein in animal feed, and soyoil, used in foods and soy-based biodiesel fuel.
"I think there is a very strong US crush pace, with the big domestic crush margins," said Dan Cekander, analyst at Newedge USA in Chicago.
Traders also noted continued rains in saturated areas of Argentina's crop belt that have stalled corn and soybean planting and could threaten yield prospects. The Commodity Weather Group on Wednesday forecast more rains for next week as well as the 11- to 15-day period.
In neighboring Paraguay, the No. 4 global soy supplier, the country's Senate approved a bill on Tuesday that would impose a 10 percent tax on soybean exports.
"You've got maybe the first sign that traders need to not be complacent with political risk in South America," Smithmier said, adding, "The market is realizing that maybe we need to put a bit of risk premium back in."
Soybeans drew background support after Statistics Canada reported Canadian production of canola, a competing oilseed, at 13.3 million tonnes, below an average of trade estimates for 13.7 million.
CBOT corn futures were boosted by weekly data from the US Energy Information Administration showing that US production of corn-based ethanol rose about 4 percent in the latest week, to 835,000 barrels per day, ending a string of declines.
"The weekly ethanol production showed a nice rebound higher. I thought that was supportive for corn," Cekander said.
CANADIAN STATISTICS
Wheat followed corn and soybeans higher but gains were limited after Statistics Canada reported that Canada's wheat harvest was the second-largest in 16 years, at 27.2 million tonnes.
The large Canadian wheat crop should help offset threats to other global wheat suppliers including Argentina, which has been plagued by excessive rains, and Australia, which trimmed its wheat production estimate this week due to dry weather.