Soybeans slumped to the lowest price since 2010 on Monday, amid expectations farmers will harvest a record crop in the U.S., the world’s biggest grower. Corn and wheat also fell.

Soybeans have tumbled 20 percent this year on signs that the record 3.816 billion-bushel U.S. harvest predicted by the Department of Agriculture will boost global inventories to an all-time high. U.S. corn output will be 14.032 billion bushels, the most ever, the USDA estimates. Parts of the Midwest received five times the normal rain in the past week, aiding plants filling kernels with sugars and starch and beans with oil and protein.

“There were beneficial rains across most of the Midwest the past week, and that will help to boost yields, especially for soybeans,” Greg Grow, the director of agribusiness for Archer Financial Services Inc. in Chicago, said in a telephone interview. “Seasonal trends are lower into October as harvest peaks and buyers are waiting for lower prices.”

Soybean futures for delivery in November declined 1.2 percent to close at $10.2925 a bushel at 1:15 p.m. on the Chicago Board of Trade, after touching $10.26, the lowest for a most-active contract since September 2010. Prices declined 1 percent last week.

Corn futures for December delivery dropped 1.1 percent to $3.675 a bushel on the CBOT, after falling 1.5 percent last week, the first decline in three weeks. The price touched a four-year low at $3.58 on Aug. 12.

Wheat futures for December delivery fell 1.4 percent to $5.545 a bushel.

Increased supplies of crops, including soybeans and corn, are helping reduce global food prices, with a United Nations’ index slumping to a six-month low in July.