WASHINGTON — The U.S. Department of Agriculture in its annual Prospective Plantings report surprised the trade with a lower-than-expected forecast for 2018 soybean planted area, while corn planting intentions also were below the average of expectations but wheat area was above due to a large increase in spring wheat other than durum.

The U.S.D.A. said farmers indicated they intend to plant 88,982,000 acres of soybeans in 2018, down 1% from last year’s record 90,142,000 acres and still the second most ever if realized. Planting intentions were down or unchanged in 20 of the 31 estimating states.

Trade expectations for soybean plantings ranged from 89.9 million to 92.6 million acres and averaged 91 million.

Farmers intend to plant 88,026,000 acres of corn in 2018, down 2% from 90,167,000 acres planted in 2017, down 6% from record plantings of 94,004,000 acres in 2016 and the lowest since 88,019,000 acres in 2015. Planted area is expected to be down or unchanged in 33 of the 48 estimating states, the U.S.D.A. said.

Trade expectations for corn planted area ranged from 87.6 million to 91 million acres with an average of 89.4 million.

All wheat planting intentions were 47,339,000 acres, up 3% from 46,012,000 acres in 2017 but the second lowest in records back to 1919 after last year.

Winter wheat planted area was estimated at 32,708,000 acres, up slightly from the January estimate and from 32,696,000 acres planted in 2017, including 23.2 million acres of hard red winter, 5.85 million acres of soft red winter and 3.64 million acres of white winter.

Area planted to spring wheat other than durum was forecast at 12,627,000 acres, up 15% from 11,009,000 acres planted in 2017, including 12.1 million acres of hard red spring wheat.

Durum planted area in 2018 was forecast at 2,004,000 acres, down 13% from 2,307,000 acres planted last year.

Average trade expectations were 46.4 million acres for all wheat, 32.6 million acres for winter wheat, 11.5 million acres for other spring wheat and 2.4 million acres for durum.