ARLINGTON, VA. — Robert Johansson, the U.S. Department of Agriculture’s chief economist, projected the area planted to wheat for harvest this year to be the smallest in records extending back to 1919. At the same time, Mr. Johansson forecast areas planted to corn, soybeans and rice to increase this year. He presented his plantings forecasts in an address before the U.S.D.A.’s 96th Agricultural Outlook Forum on Feb. 20 in Arlington.

Mr. Johansson forecast the area planted to all wheat for harvest in 2020 at 45 million acres, down 158,000 acres from 2019 and a new record low.

He estimated area planted to winter wheat at 30.8 million acres, down 1% from 2019 and 11% smaller than the recent five-year average. It would be the second-smallest winter wheat planted area on record.

“Poor planting weather and continued expansion of cotton area in Kansas and Oklahoma likely hampered winter wheat seedings,” Mr. Johansson said.

He noted winter wheat area was unchanged from a year ago in major producing states such as Kansas and Oklahoma but was smaller in Montana (down 400,000 acres), Colorado (down 250,000), Nebraska (down 170,000), Illinois (down 160,000) and South Dakota (down 160,000).

“The decline in winter wheat area supported spring wheat prices,” he said. “However, saturated soils in the northern Plains may delay or prevent planting of spring wheat and enhance profitability of other crops. As a result, other-spring wheat planted area is expected to decline slightly in 2020-21. Durum planted area is projected to rise from the previous year’s low level but remain below the five-year average.”

Mr. Johansson said current prices point to a large corn crop in 2020 — the soybeans-to-corn price ratio has dipped to four-year lows. He noted that local demand and transport costs will drive regional economic signals to plant corn or soybeans this spring.

“Right now, the soybean:corn price ratio favors the planting of more soybeans in the Dakotas compared with a signal to plant more corn in the eastern Corn Belt,” he said.

He forecast area planted to corn for harvest this year at 94 million acres, up 5% from 89.7 million acres in 2019. It would be the largest area planted to corn since 2016, also at 94 million acres. The record corn planted area was 97.3 million acres in 2013.

Mr. Johansson projected farmers will plant 85 million acres to soybeans this spring, up 8.9 million acres, or 12%, from 76.1 million acres in 2019.

“Last year’s planting difficulties resulted in a 13.1-million-acre year-to-year decline in soybean planted area, equivalent to more than 600 million bus at trend yields,” he said. “Thus, soybean beginning stocks in 2020 are projected down sharply relative to a year ago. Those lower carry-in supplies, combined with continued global demand growth, are expected to support an increase in soybean area to 85 million acres in 2020.”

Mr. Johansson forecast farmers will plant 3.1 million acres to rice in 2020, up 0.6 million acres, or 21%, from 2.5 million acres in 2019. It would be the largest area planted to rice since 3.2 million acres in 2016.

Mr. Johansson projected area planted to the eight principal field crops at 250.7 million acres, up 5% from 238 million acres in 2019.