U.S. soybeans climbed to an eight-month peak on Wednesday, while corn traded at its highest in six months as short-covering by investment funds buoyed agricultural markets amid concerns over South American weather.
Wheat gained for a third consecutive session to trade near Tuesday's four-month peak.
The Chicago Board of Trade most-active May soybean contract rose as much as 0.8 percent to $9.89-1/2 a bushel, the highest since Aug. 11.
May corn gained 0.5 percent to $3.86 a bushel, matching Tuesday's six-month high, while July wheat added 0.5 percent to $4.95-1/2 a bushel, close to last session's four-month top of $4.96 a bushel.
"We have issues with Argentina's bean crop because of the wet weather and Australia is facing dry planting weather," said Simon Clancy of IKON Commodities in Sydney. "These factors are supportive for markets but not driving them to the extent we have seen. This action is mainly fund buying."
Commodity funds were heavy net buyers of CBOT soybean and corn contracts on Tuesday, with estimates in a wide range following high-volume trade, traders said.
Trader estimates of net fund buying in soybeans ranged from 20,000 to 26,000 contracts, and in corn from 8,000 to 25,000 contracts. The funds were also net buyers of 9,000 wheat contracts.
There are some fundamental factors supporting soybeans and corn. Rains this month in Argentina slowed the soybean harvest and delayed export shipments, prompting some traders to extend long soybean bets.
Wet weather was forecast next week in the northern half of Argentina, further threatening yields and delaying harvest, said Dan Cekander, analyst at DC Analysis LLC.
Port delays in Argentina were seen extending the U.S. soymeal export season, while tight corn supplies ahead of harvest in Brazil were forcing some buyers to turn back to the United States for corn.
Brazil decided on Tuesday to eliminate an import tax on corn shipments from countries outside the Mercosur trade bloc to facilitate imports amid tight local supplies.
Brazilian corn consumers are facing tight supply of the cereal despite a record 2015/16 crop, after producers sold huge volumes abroad taking advantage of favorable exchange rates.
The U.S. Department of Agriculture earlier said exporters sold 241,516 tonnes of U.S. corn to unknown destinations, 380,000 tonnes of U.S. soybeans to Mexico, and 105,412 tonnes of U.S. soymeal to unknown destinations.