Every now and then, official Washington lifts up a rock and makes a startling discovery. They've done it again and found that the small family farm, commonly thought to have gone the way of the dinosaur, hasn't vanished after all.

It turns out that the small farm, which most experts had relegated to the fossil bed a decade or so ago, is flourishing. To the surprise of everyone concerned, about 600 people--many of them farmers, many of them young--showed up for a federal small-farm research symposium last week.

In recent weeks, similar gatherings have been held under state aegis at Kansas State University and in Florida, and in Washington under National Farmers Union sponsorship. While the statistics and the interest indicate the small farm is alive and well, official Washington seems not quite certain how to deal with the phenomenon.

Most government farm-assistance programs are oriented toward big producers; the research is big-production oriented; the commodity support programs tend to favor the largest farmers; equipment research is aimed at large-scale farming.

The imbalance is reflected in the Department of Agriculture's multimillion-dollar research program, which allocates less than 1 percent of its budget ($3.8 million) to small-farm problems. And that deals only with the Northeast and the South.

"A question of resources," says Dr. Jerrel B. Powell, assistant director of USDA's national research center at Beltsville.

At USDA headquarters, there are slight signs of an awakening interest in the issue of small farms. President Reagan dispatched a White House aide to the national symposium at Beltsville last week, with a letter of support for small farming.

But as Congress gropes to write a new farm bill, the term "small farm" is rarely heard and its problems are not addressed. Resolutions attesting to the importance of the "family farm" are adopted routinely, but little more happens.

Notwithstanding all of that, the Beltsville small-farm research symposium was a booming success. About a third of the 600 delegates were farmers--unusual for a research meeting--and they came from almost every state.

They heard William C. Norris, chairman of the Control Data Corp., call for a major new national program to boost small farmers, including a redirection of research to emphasize economical farming and small-scale technology, tax credits and land-financing assistance.

The key signal out of Beltsville was that while there is quibbling over definitions and numbers, small-scale farming is showing signs of new vigor all around the country. It is, however, a different sort of farming from that of the 40-acres-and-a-mule era, with an emphasis on specialty crops and farming by part-time agriculturalists.

The growth of farmers' markets in urban areas is stimulating fresh fruit and vegetable production on small farms. Pick-your-own operations, which cut farmers' energy and labor costs, are catching on in many areas. High-profit items such as raspberries, apples, asparagus, grapes and rabbits increasingly are raised on small plots.

"You don't hear much about small farms because nobody's out there waving the flag," said Howard W. Kerr, Beltsville's small-farm research coordinator for the Northeast. "But it's like a Mount St. Helens, about to erupt, and the public is hankering for information and guidance."

Kerr reported last week that in the 12 northeastern states his research projects cover, at least 42 percent of farms fit the "small" category, with West Virginia, New Hampshire and Rhode Island showing 60 percent in that category. Kerr's survey of county agents projected a 16 to 17 percent net growth in small-farming operations by 1990.

Through all of this, however, small farmers have special problems and their message at the symposium was that if government is going to help agriculture, it ought to pay more attention to the little guy.

"There is a dichotomy," said Dr. Sylvan H. Wittwer, assistant dean of agriculture at Michigan State University. "There is a greater number of large and small farms, with middle-sized operations decreasing. Yet much of the research in the past has worked against the small farm."

Wittwer and others underlined a major problem: a lack of specialized equipment for small farms. The major U.S. manufacturers, they reported, have emphasized high-cost, big-scale equipment that small farmers can neither use nor afford. "We have not kept pace with what is needed for small-scale implements," Wittwer said. "We are importing these things from Japan and Europe, when they are available."

Others were critical of USDA's extension service, which they portrayed as serving large farmers at the expense of the smallest who need information and guidance. "The inadequacy of extension for small farms is a travesty," said Wittwer.

It took a farmer to put it in the bluntest of terms. Rod Parker, who farms near Clinton, said, "As farmers, we have to confess we are so ignorant we don't even know the questions to ask . . . We small farmers need to know more about using financial leverage, about production, about marketing . . . The bottom line is whether the research is going to make me money or if it has potential. If you're going to spend my money on it and it doesn't have that promise, I'd say forget it."

Parker got a lengthy ovation. Pretty noisy for a dinosaur.