Analysts were expecting net sales of 600,000 to 1 million tonnes.
The cancellations included 807,000 tonnes intended for China, the world's top soya importer, and 444,000 tonnes for "unknown" destinations, which the market believes could also be China, traders said.
The most active soyabean contract on the Chicago Board Of Trade was down 1.25 percent at $9.04-3/4 a bushel by 1544 GMT.
The market was also assessing the latest Chinese import data: it imported 7.38 million tonnes of soyabeans in January, down 13 percent compared to a year earlier, but up 29 percent from December, according to Chinese customs data.
The data did not provide a breakdown of suppliers. How much of that volume came from US soyabeans is not yet clear. USDA is slated to release a combined export sales report for the weeks ending Jan. 10 through Feb. 14 next week.
Also, China's growing reliance on South American soyabeans could be reinforced by a strong harvest in the region. Argentina's soya crop is expected to reach 52 million tonnes during the 2018-19 season, up from 50 million tonnes previously forecast, the Rosario Grains Exchange said late on Wednesday.
Corn also fell, as did wheat on technical selling.
As of 12:16 p.m. CST (1816 GMT), CBOT March wheat was down 14-3/4 cents at $5.07-1/2 per bushel, after hitting $5.07, the lowest since Jan. 3. CBOT March soyabeans were down 12-1/2 cents at $9.04 per bushel while March corn was down 4 cents at $3.74-3/4 a bushel.