Behind their CB microphones and inside their heated tractor cabs, the estimated 5,000 farmers who clogged the streets of Washington yesterday were acting out a tradition of American protest nearly as old as the republic itself.

For more than two centuries, American farmers caught in periodic cycles of debt and drought have erupted against the economic hardships of their chosen life and demanded a larger share of the American dream.

From Shay's Rebellion in Massachusetts in 1786 and the "Whiskey Rebellion" of the 1790s to the larger-scale agrarian movements of the 19th Century, the protests have called -- violently and nonviolently -- for recognition of the farmer's seminal role in the structure of socitey.

"Burn down your cities and leave our farms and your cities will spring up again as if by magic," said William Jennings Bryan in his classic statement of the farmer's case before the Democratic convention of 1896. "But destroy our farms and the grass will grow in the streets of every city in the country."

Yesterday the signs on many tractors thronging into town said the same thing: "Destroy the Farmer and You Destroy America."

The protesting farmers of 1979, however, are no back-country rustics pleading for food and shelter.

They are small to medium-sized businessmen -- basically middle class -- caught in the same inflationary pressures squeezing other Americans, but businessmen for whom costs have been rising far faster than they have for the population at large.

Rolling into Washington in $50,000 tractors whose tires can cost $800 apiece, they warn that the loss of America's independent family farms will leave the nation's food supply in the hands of huge agribusiness cartels and Arab and Japanese speculators.

Yesterday's protesters included such people as Marvin (Big M) Meeks, a snuff-dipping, 300-pound cotton grower from Plainview, Tex., who has paid no income tax the last few years, he said, because he has had no income.

Meeks, a former salesman who runs his family's 2,300-acre spread with his father, said 1978 was a good crop year but because of the vast cost of farming he barely broke even.

To get him to Washington, he said, half a dozen neighbors chipped in $600 apiece.

Maynard Wright, 63, and his wife Lucille, 60, grow wheat and beans on 3,000 acres near Bird City, Kan., but said they produce a crop only once every two years due to lack of soil moisture.

They haven't made a profit, they said, since 1974.

Their son Donald, 31, said he was out of debt once -- in 1974 -- but now owes $60,000, and is spending $3 a bushel to raise wheat that he ends up selling for $2.50.

Bill Qualls, 45, of Lake City, Ark., on the other hand, did make a profit on the 1,800 acres of cotton he works with his three brothers. But the $20,000 net, he said, was split four ways.

"In 1976," he said, "we grossed a half million dollars but I had to borrow to pay my taxes because the cost of production had increased tenfold."

Despite their debts, however, most of the farmers arrived here with the costly toys of a middle-class consumer society.

Delmar (Goldinger) Foster, 37, of Hoxie, Kan. led a parade of tractors in from Maryland in his four-wheel drive pickup equipped with a sophisticated Citizens Band radio and an expensive radar detector at the top of the wind-shield. Tucked into a pouch in the passenger's door were two boxes of 9-millimeter Luger cartridges, but Foster said he didn't have his pistol with him.

Foster has been a farmer most of his life, he said, except for a seven-year stint as a trucker, and "the best year I ever had was last year, cropwise... and I lost $22,000."

He still does some trucking, he says, when his children need something special.

Foster was cooperating with the police and calming the farmers' fervor as much as possible, even as some were radioing back to him that they wanted to drive to the middle of the action.

"I tell you," he said, "every one of those guys back there's got a different idea... It's amazing, really, that we got across the country."

Though the tractor-driving protesters were the most visible, others fanned out on foot with wives and children for a peek at the Smithsonian, or mixed their lobbying with sightseeing at the Capitol.

Cattle and grain farmer Conrad Cox, 36, said he had flown in from his home in Long Island, Kan., to "see what really does unfold and hope for the best... I've never been to Washington before," he said.

Cox describes himself as an "average" Kansas farmer, with 180 head of cattle, 160 acres of corn and 300 acres of wheat. He loses money on the corn, makes it up on the wheat, he says, and his net worth is $700,000.

"My concern is the future," he said. "You could go to Las Vegas and there's no bigger gamble than farming."

But Cox's wait-and-see attitude was not always the rule as the occasional violence of the day was to prove.

As day turned into evening Tommy Kersey, a peanut and livestock farmer from Unadilla, Ga., was protesting city plans to keep the tractors barricaded on the Mall.

"Them boys didn't drive their tractors 3,000 miles to sit still, they want to be visible to the country," he said.

And out on the Ellipse a group of angry corn and soybean farmers from Georgia heard Randall Odem, one of their number, promise violence if their needs aren't met.

"You take a drowning man and he doesn't care what he does," said Odem, who said he lost $25,000 last year despite a "fair" crop of corn.

"You don't know what farmers will do until they do it," said Roger Mahagan, a young farmer from Hale Center, Tex. "It's like a hail storm. You don't know when it'll stop until it does."