CHICAGO (Reuters) -- U.S. soybean futures fell to life-of-contract lows on Tuesday and the most actively traded contract hit its lowest in a decade as an escalating U.S.-China trade war darkened U.S. export prospects, analysts said.
Corn futures also hit contract lows as the U.S. harvest expanded, while wheat futures rose on tightening global supplies.
Chicago Board of Trade November soybeans settled down 9-1/2 cents at $8.14 a bushel after dipping to $8.12-1/4, a contract low and the lowest for a most active soybean contract since December 2008.
Soybeans sagged after Beijing added $60 billion of U.S. products to its import tariff list in retaliation for President Donald Trump's planned levies on $200 billion worth of Chinese goods.
The measures are the latest escalation in an increasingly protracted trade dispute between the world's two largest economies. China is by far the world's top soy consumer, while the United States is the No. 1 soybean producer.
The U.S. harvest of corn and soybeans is under way, and the U.S. Department of Agriculture last week projected record-high yields for both crops.
"The (weakness in) beans especially is all about tariffs ... Meantime, we've got generally very solid yields," said Jack Scoville, analyst with the Price Futures Group in Chicago.
After the market closed on Monday, the USDA said the U.S. soybean harvest was 6 percent complete, above the five-year average of 3 percent.
U.S. corn harvesting was 9 percent complete, ahead of the five-year average of 6 percent, the USDA said.
CBOT corn futures followed soybeans lower, with benchmark December corn finishing down 4-3/4 cents at $3.43-1/4 a bushel after hitting a contract low of $3.42-1/2.
Wheat bucked the weaker trend, with CBOT December wheat ending up 4-1/4 cents at $5.10-1/2.
Wheat drew support from possible frost damage over the weekend in western Australia, as well as news that Russia's agriculture ministry projected 2018/19 wheat exports at 30 million tonnes, below the USDA's last estimate of 35 million.
After the CBOT close, Egypt's state grains buyer GASC booked 180,000 tonnes of wheat for shipment over Nov. 1-10 and a further 295,000 tonnes for shipment over Nov. 11-20. GASC said that all of the wheat was Russian, apart from one 60,000-tonne cargo of Ukrainian wheat.