Soybeans had climbed the previous two sessions, buoyed by worries that dry weather could reduce yields in Argentina. But weekend rainfall alleviated some of those concerns and prompted traders to take profits on short positions.
Soymeal futures fell about 1 percent before trimming losses, ending down about 0.6 percent. Argentina is the top exporter of soymeal and soyoil.
Soyoil futures followed soybeans and soymeal lower, despite Malaysian palm oil prices rising to a one-week high.
The US Department of Agriculture announced a sale of 110,000 tonnes of US soybeans to China.
There was an explosion at the General San Martin port in Argentina's grains hub of Rosario on Wednesday, affecting shipping activities, the CIARA-CEC chamber of export companies said.