While lawn-obsessed homeowners in metropolitan Washington fret about liver spots on the rye grass and fungus on their fescue, one man in the federal government, at least, is fighting for their turf.

Jack Murray, 39, of the U.S. Department of Agriculture's Beltsville experimental station, is a virtual guru of grass. As a consultant to everyone from sharecroppers to shieks, Murray spends these hot August days sweating and stalking around the government's 16 acres of test tube lawn.

Grubs and beetles may laugh at Washingtonians slaving to turn the backyard into greener pastures - but Jack Murray laughs last.

Every year, Murray's office receives about 2,000 pleas for advice. Six months ago, the Saudi Arabian government, enthralled with the notion of grass sprouting in the desert, phoned to ask how they could best decorate the runways and terminals outside their airports.

The Saudis had their heart set on Kentucky bluegrass, but Murray talked them out of it.

"It won't grow over there," he said, wiping the sweat from his brow. "Too hot."

The Saudis will have to settle for Bermuda grass, a strain that thrives in hot weather. Come fall, the plan is to dispatch cargo ships laden with sod. Murray, a drawling good old boy from Jesup, Ga., warned them that it would be expensive. "But, they didn't care about the cost," said the research agronomist whose turf is turf.

Constituents all over the country write their congressmen about bill bugs, white grubs and other suburban scourges, Murray says, and he ends up tending to their plight.

A farmer with 1,000 acres might not write his congressman," says Murray. "But a homeowner with a two acre plot doesn't hesitate a minute. Sometimes, we get spread pretty thin out here."

The most common complaint, Murray says, is "brown patch" - an ugly disease that turns grass brown. It respects neither money or status, sullying with equal energy bo the backyards of Southeast Washington and the fairways at Burning Tree.

"No grass is totally resistent to "brown patch,"" said Murray. Still, he is trying to breed a disease resistant strain at Beltsville.

"We're willing to try anything," he said.

Murray is now gearing up for Turf Day, Aug. 22, the experiment station's annual superbowl of sod. Every year, homeowners, lawn care specialists, seed and pest control people and park managers descend on Beltsville for a "Dear Jack" session.

The day is devoted to examining the 25 to 30 grass experiments Murray supervises."Turf is an art and a science," he said. "You can tell a lot about someone by the way they keep their law."

What most homeowners seek, he said, is "the perfect lawn with no work, Utopia."

While there is no such thing as the ultimate lazy man's lawn, Murray says an acceptable patch of green is within reach, even for sloths.

Zoysia is such a grass, as is tall fescue. But bluegrass if fickle.

Where most homeowners make mistakes, according to Murray, is fertilizing too much in the spring and not enough in the fall. It should be the other way around.

Murray graduated from the University of Georgia, earned a master's degree at the University of Nevada, moved to Beltsville to take a job with the USDA and rapidly became the acknowledged king of grass.

When he moved into his house on Sellman Road, however, he kept the job a secret and quietly went about planting a special blend of Kentucky bluegrass. "I wanted to see how my law would turn out," he said.

Neighbors soon began beating a path to his back door. Murrya" grass was greener. Now he's the star of Beltsville's backyard barbecue circuit. Everyone wants to know what strain of grass to plant. He tells them that it all depends.

Shady backyards often show promise when planted with fine leaf or red fescue, while Kentucky bluegrass does well in open, sunny areas. In hot weather, homeowners who have planted zoysia or bermuda grass have the least to worry about.

"August is a stress time for cool season grasses like Kentucky bluegrass, tall fescue and rye, but it's the best season for Bermuda and zoysia," noted Murray.

An exemplary lawn, say some realtors, can add about three percent to the selling price of a home and shorten the time it takes to sell it.

But, in Murray's view, the American quest to achieve the perfect lawn has been dealt a serious setback since the government banned the pesticide chlordane. He predicts a virtual "holocaust" of white grubs as a result.

Aside from spraying for bugs, there is little that harried homeowners can do to improve their back lots, Murray said.