U.S. farmers will plant 2.1 million fewer acres of corn, soybeans and wheat this year, the U.S. Department of Agriculture said last week at its annual outlook conference.

The agency projects corn plantings at 92 million acres, up 3.3 percent from last year, while soybean plantings are expected to fall 4.7 percent to 85 million acres. The USDA sees wheat plantings at 47 million acres, down 1.7 percent, including the lowest winter wheat plantings since 1909.

The 2019 U.S....