The farmers organization that created havoc with a "tractorcade" farm policy protest here six years ago is back, but this time there are few tractors and no havoc. The farmers have seen havoc enough, they said, in their bank books back home.

About 2,000 members and supporters of the American Agriculture Movement gathered at the Jefferson Memorial yesterday in a cold drizzle, bearing signs decrying falling prices and government inaction. They cheered lustily for Jim Hightower, head of the Texas Agriculture Department, who said federal farm bureaucrats "couldn't run a roadside watermelon stand if we gave them the melons and had the Highway Patrol flag the cars down."

The farmers marched solemnly from the Tidal Basin to the Agriculture Department and on to the White House to demand that the administration expand efforts to keep failing farms afloat. They will continue the lobbying effort at the offices of senators and representatives today and tomorrow.

The farmers carried 250 white crosses, each bearing the name of a colleague gone bust, which they said represented the number of family farms that fail every day. The cross carried by Donna Shoop of Memphis, Mo., bore her own family name. The Shoops are broke and selling their 625-acre farm after 27 years, she said, because the prices they get for grain and hogs won't pay the production costs.

The farmers, who came from as far as Arizona and Texas, said a combination of low prices and continued high interest rates has left them on or over the brink of disaster, and many said that with only a few weeks until planting time, they've been unable to secure loans to put in this year's crops.

"This situation affects people," said David Senter, AAM's national director and a fourth-generation farmer. "Some commit suicide, some just quit, some drink and some go out and get a job. But it made me mad and I'm going to do what I can to change it."

The farmers want two things: Short-term financial aid in the form of federal loans so they can plant this year and reinstitution of a "parity" policy under which the government guarantees them a profit by establishing minimum prices based on annual average production costs.

The House and Senate have passed a short-term financial-aid package, but President Reagan reportedly will veto it. Similarly, government-enforced parity, which was U.S. policy from 1933 to 1952, is opposed by the administration, which favors a free market.

Many of the marchers said they were conservatives who voted for Reagan and felt betrayed. They cheered for Hightower, a Texas Democrat, when he said, "Ronald Reagan promised us a seven-course dinner and now we find out what it is -- a possum and a six-pack."

And they cheered for Sen. Tom Harkin (D-Iowa), who said the solution to their problem "is right down the street, a block away. Ronald Reagan can sign that bill."

The AAM created massive traffic jams during its last protest in 1979, but this year the aim apparently is conciliation. When marchers, accompanied by three tractors and a phalanx of motorcycle police, approached the Agriculture Department front doors yesterday, they were told by uniformed police they could only convene across the street on the Mall, and quickly complied.

The marchers also were stopped short of the White House by Park Police, who halted the march about midway across the Ellipse. "I guess this is as close as we're going to get," said Senter apologetically. The marchers responded by gentle renderings of "God Bless America" and "America the Beautiful."