The most active corn contract for December delivery went down 6.25 cents, or 1.7 percent to close at 3.6075 dollars per bushel. September wheat delivery fell 16 cents, or 3.15 percent to close at 4.92 dollars per bushel. November soybean delivery was 0.5 cent lower, or 0.06 percent to close at 8.715 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.
CBOT corn futures fell to contract lows on forecasts for crop-boosting rain and milder temperatures in the heart of the U.S. corn belt.
Wheat futures tumbled more than 3 percent on dull export demand and improving spring wheat crop conditions.
The U.S. Department of Agriculture's weekly crop progress report released on Monday showed that 75 percent of the U.S. corn crop is rated good or excellent (down 1 percentage point), 71 percent of the U.S. soybean is rated good or excellent (unchanged) with 80 percent of the U.S. spring wheat is rated good or excellent (up 3 percentage points).