The average age of farmers has increased so much in the tough times of the 1980s that a former Agriculture Department economist says retirements could force another round of farm consolidations by the turn of the century.

Matthew G. Smith, now with the Minnesota Department of Revenue, says the graying of American farmers was a prominent issue in the 1950s and 1960s. But a boom in exports and farm incomes attracted more young people in the middle and late 1970s, and for a while the face of agriculture got a bit younger.Now, however, "nearly half of all farm assets are owned by farmers who will probably retire within 10 years, yet fewer than one in three younger operators is in a strong position to purchase those assets," Smith said.

"With the number of new farmers again declining, with many middle-aged farmers in financial difficulty, and with a steady rate of retirement of older farmers, the total number of U.S. farms may drop rapidly between now and the year 2000."

Smith reported his analysis in RDP, or Rural Development Perspectives, a magazine published by the department's Economic Research Service, where he formerly worked.

"If these trends continued unchecked, the share of farmland owned by absentee landlords may rise, growth in farm efficiency may slow, and businesses serving the farm sector will find themselves competing for slices of a shrinking pie," he said.

The net number of new farmers younger than 35 in 1974 averaged almost 29,000 a year from 1974 to 1978, he said. From 1978 to 1982, the number of new farmers under 35 dropped by nearly 40 percent to fewer than 18,000 a year.

A middle group, 35 to 54 years, which grew from 1974 to 1978, shrank in 1978-82. Thus, in this age group, which normally includes farmers both entering and leaving farming, more were leaving than entering by the early 1980s.

"Meanwhile rates of net departures among older operators (55 and older) were relatively stable, reflecting the fairly predictable process of retirement," Smith said.