The bureaucrat, wearing blue jeans, a work shirt and white wool socks, labors in a lettuce field 15 miles from the White House, rototilling the mud. Four years ago, he found a parasite in that mud that could save the nation's lettuce industry $350 million a year. The discovery could make the bureaucrat, who hates to be called a bureaucrat, the Jonas Salk of lettuce.

In a nearby hilltop laboratory surrounded by a barbed-wire fence, another bureaucrat eats a half-pound of raw hamburger for lunch, trying to infect himself with a parasite that kills sheep. He wants to know what the parasite does to people, and he could not find anybody else who would eat the meat.

North of the parasite lab, a third bureaucrat watches a dog sniff milk. If the dog sits down, that is the signal that the milk came from a cow in heat. The bureaucrat is trying to figure out how the dog knows.

The three bureaucrats -- a plant pathologist, a parisitologist and an animal physiologist -- ply their esoteric trades along with 447 other government scientists in laboratories spread over 7,225 acres of suburb-encircled farmland in Beltsville. It is the scientific Mecca of the farming world.

Mention of the Beltsville Research Center evokes who-cares shrugs from Maryland suburbanites who drive past it daily on the Capital Beltway and covetous sighs from developers who would subdivide the farmland and sell half-acre lots for $25,000 each. Yet, the graceless, flat-sounding name "Beltsville" is a synonym for American genius among wheat scientists in the Soviet Union, hog experts in Yugoslavia and potato growers in Pakistan.

The bureaucrat-scientists at Beltsville, many of whom grew up milking cows and baling hay on the farms in the Midwest, have made hundreds of discoveries that have radically changed the livestock and crops raised on American farms and contributed to an equally radical -- and much-critized -- concentration of ownership in agriculture, the nation's largest industry.

Because of pioneering discoveries at Beltsville, dairy cows produce twice as much milk as they did 30 years ago and hogs are half as fat, broiler chickens reach muturity in six weeks instead of three months, sheep have better and warmer wool, corn yields have more than tripled in 40 years, flowering plants can be tricked into blooming year-round and a breed of compact turkey -- the Beltsville turkey -- was developed to fit into American refrigerators.

For 70 years Beltsville has been the linchpin of the Department of Agriculture's effort to help farmers produce affordable food, a research effort that many economists agree has been one of the smartest investments of taxpayers' money in the world. Agriculture economists say consumers and farmers reap a return of nearly 50 cents on every dollar spent by USDA on research. This is a bargain compared to the 10 to 20 cents on the dollar that private industry typically earns on its research.

With their remarkable productivity the scientists at Beltsville lead a charmed life as far as money is concerned. The House and Senate committees that review USDA's research budget almost always approve more money than USDA asks for. This year USDA asked for $348 million for agriculture research but got about $375 million.

While reports of escalating inflation have forced President Carter and Congress to threaten to cut up to $30 billion from the 1981 federal budget, agriculture research has not been mentioned as vulnerable to the ax.

The USDA scientists who came off the farm throughout this centry to perform their research miracles at Beltsville have solved so many problems in the mass production of food that they have helped create a farm economy dominated by big-money farm corporations that can afford mass-production technology. More than half the nation's food now is produced by just 200,000 farms, while the total number of farms continues to dwindle from a peak in the 1930s of 7 million to less than 2.7 million today.

The chicken industry, which owes an immeasurable debt to Beltsville research, is agriculture's most striking example of concentrated ownership. Only one percent of the 30,000 chicken farmers in the country own their chickens -- the rest are raised for a handful of giant corporations.

USDA's contribution to agri-business has begun to disturb top officials in the department. Secretary Bob Bergland recently said the government would no longer help develop farm machinery and appointed a task force to study how USDA can avoid research that displaces farm labor.

Out in bucolic Beltsville, however, where cows walk around with windows in their stomachs and bees are deceived into believing that soybean flour is pollen, the politics of agriculture are secondary to finding out such things as how much newsprint, instead of conventional feed, a dairy cow can eat and still produce good milk.

Scientists at Beltsville say they don't make policy and that they would hate to have to sit at a desk in downtown Washington with all the USDA bureaucrats who do.

"In the fall and spring here at Beltsville you can hear the geese fly over," says Lowell T. Frobish, an Illinois-born animal scientist who specializes in nutrition for turkeys and hogs. "If I had to be in the concrete jungle downtown, I'd go crazy."

In their neo-Georgian laboratories, surrounded by greenhouses and rolling fields in which grow virtually every kind of grain, vegetable and fruit known to man, the scientists direct their energies at the particular. Ray Webb, for example, is a potato man -- probably the world's best informed and most influential potato man.

Webb is a solid, fit man of 60 with short brown hair and a ruddy face worn from years in the vegetable fields. He came north to Beltsville 27 years ago from his native Louisiana with impeccable credentials for developing new vegetable varieties. The move north from Louisiana State University to Beltsville was comparable for Webb to the promotion of a small-time television newsman to an on-camera job with a major network.

"I thought the opportunities for pursuing a broader range of activities in vegetable improvement were much greater here," says Webb, a GS-15 who makes $51,000 a year and lives just across a fence from the Beltsville pastures. His walk to work takes 12 minutes.

There have been only four top potato men at USDA since 1913. Webb is arguably the best. He has developed, along with his potato staff of three scientists and seven technicians and an annual budget of about $300,000, three well-received varieties of russet (dark-skinned) potatoes and is working on perfecting his fourth, which has yet to earn a name. For the moment the potato is called 8972-1.

8972-1 is a handsome potato, and, as Webb describes it, 8972-1 could go a long way to making the East Coast potato industry competitive with the much-ballyhooed Idaho potato. This newest Beltsville potato will yield about 5,000 pounds more potato weight to the acre than the Bellrus potato, which Webb developed and which now is being marketed by the R. T. French's Co., in the Washington area. It has all the disease and insect resistance of the world's best potatoes, will grow plump and smooth, has good processing white flesh with little after-cooking darkening and it tastes good.

Webb, who supervises potato-growing experiments up and down the East Coast as well as in Pakistan, Nigeria, Korea and the Philippines, invites his friends and colleagues to his office in Building 004 at Beltsville to taste-test his new potatoes.

"We get some people in here to taste 'em. This is to tell me if it has consumer acceptability. This isn't completely scientific, it's an art," says Webb.

Americans eat an average of 125 pounds of potatoes a year and almost all of the baked potatoes eaten on the East Coast come from Idaho and the Pacific Northwest.Webb thinks shipping a potato all the way across the country to be baked is dumb and wasteful. So he's creating a dozen new potatoes that will stand up to the inconsistencies of East Coast weather. n

Those problems are particularly troublesome in Maine, which despite its well-known potatoes has had difficulty producing a baking potato that is uniform in both size and texture.

Idaho potato growers are understandably concerned with Webb's intent to cut into their East Coast sales. The office of Sen. Frank Church (D-Idaho) recently called Webb, asking what this potato business was all about, the scientist says. Wary of Church's influence, Webb says he hopes that politics won't interfere with his potato plans. Church's office denies making the call.

Webb, who says he won't retire until he develops the potatoes he thinks the country needs, claims consumers on the East Coast can save 4 1/2 cents per pound of potato in transportation cost if a large, tasty baking potato blossoms on this side of the country.

In his Beltsville office, surrounded by technical potato literature and a few selected potatoes of his own invention, Webb enjoys looking at a large relief map of the United States and discussing the future: "Now I'd like to have the opportunity to grow high quality [baking] potatoes all the way from the southern tip of Florida to the northern tip of Maine."

The potatoes that Webb decides have a future undergo their first field test -- as do all crops -- in the dirt of Beltsville. It is, generally speaking, lousy dirt for growing plants -- a fact that the Department of Agriculture knew when it began research there in 1910.

At that time USDA was being presessured by the War Department to abandon its 400-acre experimental farm in Arlington where the Pentagon is located. USDA agents went out to assess the farmland at Beltsville, disguising themselves as farmers so landowners wouldn't jack up the price of land. They reported back to Secretary of Agriculture James Wilson that the land was cheap, but worn-out by over planting and not that fertile in the first place. Wilson got mad.

"Anyone can grow a crop on good land," he reportedly snapped. "Buy it, and use plenty of cow manure."

USDA bought 475 acres at Beltsville in 1910, liberally applied manure and by the 1940s had increased its landholdings to 14,000 acres. Since then, the farm has shrunk nearly in half, with various federal agencies such as Treasury, Interior and the National Aeronautics and Space Administration nibbling at the farm's north and south borders.

The nibbling has apparently stopped, and none too soon for many of the scientists at Beltsville, who say they despise urban crowding and would leave USDA if they were forced to work as most bureaucrats do.

Peter B. Adams, the plant pathologist who rototills his own crops and has discovered a parasite that could cure the nation's most serious lettuce disease, says he wishes Beltsville were located in Kansas or someplace a little farther away from all the people.

"I would do any thing I could to get out of working around cities. I hate cities; I hate crowds. You could make a pretty good case that I hate people, at least, people in groups," says Adams.

What Adams likes is to spend time with farmers, whom he praises as the "biggest bunch of gamblers we have in this country," and to spend time with his lettuce.

"I feel like I learn a lot when I'm out there in that damn field. When I'm out there working on my lettuce, I'm doing more than that. I'm constantly studying how these diseases work," says Adams, 44, a GS-14 who makes nearly $40,000 a year, is married, has two children and brags that he hasn't worn a tie in two years.

The plant pathologist's nemesis is a fungus called "lettuce drop that infects plants through the soil they grow in. Lettuce drop is the nation's most destructive lettuce disease, destroying between 5 and 25 percent of the annual lettuce crop and costing farmers more than $350 million a year in lost revenues.

Back in 1976 at Beltsville, Adams was having trouble infecting his plants with lettuce drop. He examined the dirt and found an unidentified micro-parasite that was killing the lettuce fungus. Adams named it sporidesmium sclerotivorum and is now figuring out how to produce the stuff in commercial quantities.

Adams goes to work at 6:30 a.m. and comes home about 4 p.m. He works most weekends, tending his plants. During the current spring planting season, when he's getting his 25 plots of lettuce ready. He works up to 16 hours a day. He claims he's got the "ideal job" and argues that unless he publishes one to two articles on his research a year "I should get fired."

The way a bureaucrat-scientist gets ahead at Beltsville is by publishing papers on his work. "There are a lot of things involved in scientific research, but basically it's publish or perish, just like at the colleges," says Paul A. Putnam, assistant director at Beltsville.

The scientists at Beltsville, along with all the 2,800 scientists who work for USDA, are paid more money if they can impress their peers with their research. Unlike other bureaucrats who are promoted on the basis of seniority and ability by their administrative superiors, scientists at USDA and many other government agencies go before peer committees where their colleagues have the loudest voice in deciding who deserves a promotion.

In a recent promotion meeting in Building 003 at Beltsville, a Ph.D plant geneticist did not receive a $7,000-a-year promotion because the members of his peer committee -- a research geneticist, a plant pathologist, a research horticulturist, a personnel administrator and Beltsville assistant director Putnam -- weren't impressed with his publication record. The geneticist had published one "senior author" article since 1975 and six "junior author" articles. "Not highly productive," the committee concluded.

Scientists at Beltsville agree that peer evaluation is the only sensible way to assess the talent of bureaucrats with such abstruse duties as breeding fatherless turkeys, propagating virus-free strawberries and classifying the quarter-million species of weevils.

Ron Fayer, the parisitologist who eats raw hamburger in his secluded laboratory to find out if store-bought meat would infect him with the parasite sarcocystis (it didn't), has no problem with the promotion system at Beltsville. But he does complain, as do nearly all the scientists, about "taking gas" from the federal Office of Management and Budget, which requires scientists to explain, two or three years in advance, what they are going to find in their research.

"That's impossible," says Fayer, "I don't have any idea what I'm going to find. I don't even know what I will be working on."

Still, at Beltsville, there is every reason to believe that the world-famous, 70-year-old farm will operate indefinitely, running on some of the most efficiently consumed federal money in government and the drive of preoccupied, contented scientists.

"I like the freedom here," says pathologist Fayer. "For the most part I'm allowed to do what I think is important." And to Fayer, parasites are what's important.