Clyde Payne, with more than 30 years of service in the Department of Agriculture, was not too surprised when Secretary John R. Block precipitously gave him his walking papers in 1981, branding him politically unacceptable.

He knew that, as state executive director of the Agricultural Stabilization and Conservation Service (ASCS) in Florida, he was subject to dismissal. He also knew he was entitled, as a career employe, to another job he never got.

So Payne walked, along with 31 other high-level USDA officials, but they also squawked. They got word last week that the Merit Systems Protection Board has cried "foul" and slapped a technical on the secretary.

John J. McCarthy, chief administrative law judge of the MSPB, has ruled that all but eight of the 32, who were state directors of two of the department's key agencies, are entitled to back pay and reinstatement to the same or comparable jobs under federal personnel protection laws.

"It is a very, very important decision," said Payne, 56, now in retirement in Jasper, Fla. "It means that I could return to the department; it affects my retirement income . . . . I never thought I was a political appointee. My whole life was with the USDA."

The 32 were dismissed by Block, who was backed up by an executive order signed by President Reagan, less than three months after the administration took office in 1981. Block and his minions called it a "reorganization," but the idea was to get the "right" people on board.

In testimony before McCarthy, departmental officials insisted that the state directorships of the ASCS and the Farmers Home Administration (FmHA) were sensitive, policy-making jobs that required having loyalists of the secretary's choosing.

Farmers Home and the ASCS, with offices in a majority of the nation's counties, handle vital rural housing, farm financing and crop loan support activities of the department. Their state and regional networks are regarded as among the most political in government, with top positions subject to change by new administrations.

Until their dismissals, all 32 of the fired state directors had Schedule A status at the department under the Carter administration, meaning that as nonpolitical professionals they were entitled to certain reassignment and income protection.

The secretary, according to the judge's findings, prevailed upon Reagan to sign an executive order in March, 1981, declaring the state directorships to be Schedule C positions, that is, political patronage slots.

Executive order in hand, Block ordered the 32 ASCS and FmHA officials out, which meant that as newly anointed Schedule Cs they were not entitled to the reassignment and pay protections they expected.

McCarthy agreed that the administration could reclassify the jobs, but he held that 24 of the 32, as military veterans, were entitled to protections and reassignment that were denied by Block.

McCarthy's decision will be final unless the department appeals the order within the next month or the MSPB reopens the case on its own motion.