Improving planting weather in the US Midwest also contributed to the weakness hanging over the market. Losses in new-crop soybeans outstripped old-crop months.
Tight domestic supplies of soybeans limited the declines in the futures market and prices for the benchmark May contract found support around the 10-day moving average.
Soymeal and soyoil futures also weakened under pressure from profit taking. Cash market dealers said that supplies of both soyoil and soymeal were running thin as many processors were shutting down for seasonal maintenance.
Argentina's soybean harvest is speeding up due to dry weather that is expected to continue over the days ahead, increasing competition for US exporters on the world market.
The US Agriculture Department said on Monday morning that export inspections of soybeans were 138,777 tonnes in the latest week, near the low end of trade forecasts for 135,000 to 350,000 tonnes.
Chinese custom data showed that the world's top buyer of soy imported 3.693 million tonnes of soybeans from the United States during March, up 11.7 percent from a year earlier. Year to date, Chinese imports of US soybeans were up 29.4 percent.