(Reuters) -Global grains merchant Archer-Daniels-Midland Co missed Wall Street expectations for second-quarter profit on Tuesday, hit by lower soy crush margins and waning demand for U.S. crops.

The company reported adjusted profit of $1.03 per share for the three months to June 30, against analyst expectations of $1.22 per share, LSEG data shows.

The company's Ag Services and Oilseeds arm, its largest business unit, suffered a 56% plunge in operating profit after South American farmers were slow to sell their crops even as demand from export buyers grew, the company said.

As soybean prices have fallen to their lowest in nearly four years, leading buyer China has shifted its focus to Brazilian and Argentinian supplies, weighing on the company's North American business.

Meanwhile, ADM's global soybean crush margins decreased on supply and demand issues while soybean oil prices fell on pressure from increased imports of used cooking oil, it said.

Global grain and oilseed supplies that companies such as ADM trade and process have surged, knocking back prices. In the United States, farmers have been sitting on larger than normal stocks as export demand for new-crop supplies have remained sluggish and China has turned to South America for much of its soybean needs.

"In Ag Services & Oilseeds, while large South American crops and shifts in farmer selling behaviors impacted results in the second quarter, we expect improved margin opportunities through the remainder of the year," CEO Juan Luciano said in a statement.