Traders shrugged off signs of strong demand for US soybeans amid the improving outlook for harvests in Brazil and Argentina.
For the week, CBOT soybeans were down 0.4 percent.
Consultancy AgRural on Friday raised its forecast for 2017-18 Brazil soybean production to 112.9 million tonnes from 110.2 million.
Forecasts for rain in Argentina in the 11-to-15 day weather outlook added pressure.
Soymeal futures also fell but soyoil rose, which traders attributed to unwinding of long soymeal/short soyoil spreads.
Soymeal futures rose 0.7 percent this week. Soyoil futures posted a weekly loss of 0.2 percent.
The US Department of Agriculture said that private exporters reported the sale of 268,000 tonnes of soybeans for delivery to China during the 2017-18 marketing year.
The government also disclosed another 129,000-tonne sale to unknown destinations for 2017-18 and a 66,000-tonne sale to unknown destinations for 2018-19.