After clashing with police in northern Virginia, the American Argricultural Movements, smaller in number but more angry in mood, rumbled back into Washinton yesterday, staged a spontaneous tractor march on the White House and descended on Capitol Hill.

Barely one-fifth the size of their Dec. 10 protest, the farmers this time proved more disruptive. After a few of them confronted police in suburban Fairfax County, the farmers marched down Pennsylavania Avenue, snarling traffic on many downtown streets and leaving government workers gawking at the spectacle.

The farmers came again to Washington to demand, as they had a month ago, that Congress take steps to gurantee higher prices for their produce. Spokesmen said they intend to remain in the capital until Congress acts.

Police shephered the parade through the District, lending protest leaders a bullhorn to direct their somewhat disorganized group and then watching with smiles as the farmers plastered passing cars with their brightly colored bumper stickers.

They're very cooperative and to tell the truth, they don't know where they're going," said Assistant D.C. Police Chief B. D. Crooke Jr., as the marchers left the Capitol. "Why, we could take them into Virginia."

An estimated 2,000 farmers and about 30 tractors, some bedecked with American flags and slogans smeared in white shoe polish, made the 90 minute trek to the White HOuse. The farmers began returning to the Capitol after one speaker warned them from the flatbed of a pickup truck that it was time to begin lobbying "our hired hands" in Congress.

Except for the arrests of seven farmers along Interstate Rte. 66 in Virginia, there were no disorders connected with the farmers' arrival in the capital. The parade itself had something of the air of a homecoming celebration at a small Midwestern agricultural college. Farmers chanted out their home states as they marched along Pennsylvania Avenue and darted in and out of the procession, taking home movies and snapshots of the event.

Only when a speaker at the White House told them of the arrest of seven protesters in the I-66 incident did the marchers become restless Cries of "let's go get 'em out" of jail echoed along the Pennsylvania Avenue sidewalks in front the White House.

"They can't do that," one woman moaned in a soft Southern drawl. "They're just good ole boys and they can't shoot at 'em and then lock 'em up."

"We're going to be heard; were not going to be Patsies," angrily shouted Alvin Jenkis of Springfield, Colo., one of the protest leaders, over the police-furnished bullbhorn. The farmers roared back their approval.

In the afternoon, the farmers, wearing red, green, gold or blue baseball caps that said "We Support the Argriculture Strike," descended on the House and Senate office buildings on Capitol Hill. There, after they had asked policemen and passersby, "Where's Rayburn? Where's Longworth?" they sounded the main themes of their return visit to Washington. They had returned, they said, "to educate our congressmen" - and to educate themselves in the ways of Washington's legislative channels, a system that is as foreign to them as the city's concrete streets and traffic jams.

Many of the meetings held on the Hill had been prearranged and some farmers had received a typed agenda from the leaders of the various state delegations. The agenda told them what room to report to and who would be meeting with them. While some of the meetings had the air of a pep rally others resembled heated town meetings.

At the South Carolina delegation's meeting in the Longworth Building, the farmers were given printed calling cards that listed on one side five "aims and objectives" of the farmer's movement. Then, they were given a little tranning in public relations by delegation leader Lynn Youmans, of Furman, S.C., who told the men: "If they (the congressmen) don't have the facts and figures, then you have them . . . You do your homework . . . Be sure you know what you're going to say . . . Be specific.

"We're getting together to do like the Arabs done," Robert Connolly, of the South Carolina delegation, said. "They had the oil and they said if we wanted it, we'd have to pay for it . . . Well we got the food and all we have to do is stick to our guns and stay in Washington until we get something done.

Connolly said delegations of farmers have organized in 41 states so far. The farmers threatened yesterday that they would not plant any crops this year if their demands are not met.

The farmers say they do not want a government subsidy to aid them financially, but say they need "100 per cent parity." Many of yesterday's protesters described their "100 per cent parity" demand this way: Farmers want the price at which they sell their products to give them the same buying power it did in the period from 1910 to 1914, when the government made its first studies of farm prices.

"What they want to do is be able to buy as many hircuts today as they did in 1910 with a bushel of wheat, said Gene Moos, senior staff analyst on the House Agriculture Committee.

Moos says 100 per cent parity could drive up the price of groceries as much as 20 per cent and could ruin chances for farmers to win support from urban and suburban legislators.

Besides parity, the farmers also say they want foreign food imports to the United States to be limited to what American producers cannot supply. And they want a greater voice in setting the country's agriculture policy.Connolly of South Carolina said the farmers will attempt to organize a lobby in Washington whose members would represent farmers from each state.

Down the hall from the South Carolina farmers, a delegation from Texas engaged in angry debate over meat imports from foreign countries with staff members of Texas Rep. Robert Krueger and George Mahon. There, the farmers talked about their frustration in trying to influence policy making in Washington.

The farmers have said they will spend much of tommorrow trying to see congressmen, particularly those who serve on the agriculture committees, and have vowed "to stay as long as it takes" to get their message across.

"We got to see the Catholics . . . they got a bloc of votes . . . we got to see the banks . . . the Chamber of Commerce," urged another South Carolina farmer.

Today, as the second session of the 95th Congress convenes, the armers plan to rally at 12:30 p.m. at the Capitol after meeting with their state sepresenatives. "They ase slowly, but surely becoming more organized." said John McMillan, a legislative aide to Rep. John W. Jenrette (D-S.C.), a supporter of the armers' movement.