Corn and soy fell on speculation that dry weather in the Midwest will firm up wet fields and allow farmers to speed up crop harvesting in the US.
Parts of Nebraska and Iowa received six times the normal October rainfall, causing fields too muddy for heavy farm equipment, according to the National Weather Service. However, dry weather may improve harvest conditions, said DTN Meteorlogix LLC.
Corn futures for December delivery fell 1.5 percent or 5.75 cents to US$3.8 per bushel on the CBOT.
Soy futures for January delivery fell 0.5 percent or 4.5 cents to US$9.02 per bushel.
About 78 percent of the corn crop was harvested as of November 16, down from 97 percent last year, the USDA said. About 95 percent of soy was harvested, down slightly from last year's 98 percent.
Prices also fell on speculation that a dollar rebound will reduce demand for US grain. The US dollar has gained nearly 10 percent against six major currencies this quarter.
Corn and soy declined with crude oil on signs that falling gasoline use will reduce demand for the grain and oilseed used in biofuels, said Dave Marshall, a farm-marketing adviser at Toay Commodity Futures Group LLC.