The price of wheat fell 3.3 percent Friday as storms were expected to deliver much-needed moisture to some fields in parts of the country.
Wheat for December delivery fell 29.25 cents to finish at $8.5675 per bushel. Corn and soybean prices also dropped.
The weekend rains are expected to help winter wheat crops that have been plagued by dry weather in western Kansas, western Nebraska and eastern Colorado.
About 15 percent to 20 percent of the winter wheat belt is considered to be too dry, Northstar Commodity analyst Jason Ward said. Crops in Oklahoma and Texas have received ample moisture at this early stage in the growing season.
Separately, the U.S. Agriculture Department reported wheat export sales fell 9 percent last week from the previous week and were about 30 percent less than the previous four-week average.
Export sales also were lower for corn as prices have continued to rise because of short supplies both in the U.S. and globally. "It's easy to see that we're just too high priced in the export market to compete," Ward said.
December corn fell 20.5 cents, or 2.7 percent, to end at $7.5275 per bushel and November soybeans dropped 26 cents to $15.225 per bushel.
Other commodities were mostly lower on concerns about global economic growth.
Oil prices fell after a new report from the International Energy Agency report predicted slower growth in demand for oil over the next five years as supplies increase. That offset worries that tensions between Syria and Turkey could threaten a crucial supply route in the Middle East.
Benchmark oil fell 21 cents to end at $91.86 per barrel, heating oil dropped 3.32 cents to $3.2239 per gallon and wholesale gasoline fell 6.28 cents to $2.8928 per gallon. Natural gas rose 0.7 cent to $3.611 per 1,000 cubic feet.
In metals trading, the price of gold fell because of uncertainty about where the global economy is headed. Many traders opted to sell holdings for a profit in case unexpected events occur during the weekend when the markets are closed.
"Going forward, it's going to be basics and headline hunting by traders," said George Gero, vice president at RBC Global Futures.
In December contracts, gold fell $10.90 to finish at $1,759.70 per ounce, silver dropped 41.3 cents to $33.669 per ounce, copper decreased 4.85 cents to $3.703 per pound and palladium ended down $11.85 at $639.05 per ounce. January platinum dropped $30.30 to $1,659.30 per ounce.