The most active corn contract for December delivery went down 6 cents, or 1.61 percent to close at 3.67 dollars per bushel.
September wheat delivery fell 7.25 cents, or 1.41 percent to close at 5.08 dollars per bushel. November soybean delivery dropped 22.5 cents, or 2.52 percent to close at 8.72 dollars per bushel.
Investors were widely worried about the impact of trade frictions between the world's top two economies after the United States began imposing a 25-percent additional tariff on Chinese products worth 34 billion U.S. dollars on Friday.
Accordingly, China canceled purchases of U.S. soybeans for delivery in the 2017-2018 and 2018-2019 marketing years, the U.S. Department of Agriculture said in a report on Friday.
Improved growing conditions in the U.S. Midwest also weighed on soybeans and corn before weekly government crop ratings later on Monday as well as monthly supply and demand forecasts on Thursday.