When Larry Blair came to Fairfax County in the 1940s, there were rows of corn ripening in fields that have now given way to rows of commuter homes, and dairy cows grazed on what are today's supermarket parking lots.

He was an extension agent for the U.S. Department of Agriculture, who came to help farmers grapple with the scientific advances in processed fertilizer and chemical insecticides, animal medicines and diet theories. It was a position he held until his retirement last month, advising ever-dwindling numbers of farmers faced with the onslaught of development.

"There may be fewer farms but they are oh so very important," said Blair last week at his Manassas home. "We cannot forget farmers. Our children have to know where their food comes from--that the milk is from a cow, not a supermarket shelf. It's important whether they live on the farm or in the suburbs."

It is Blair's deep respect for farming and his gentle sense of humor that seems to have won him the respect of Fairfax and Prince William farmers and community residents. Last week, the 64-year-old retiree was honored by more than 200 local residents at a picnic. A joint committee has been established to raise $25,000 to help pay for a recreational shelter--to be named for Blair--at the Northern Virginia 4-H Educational Center in Front Royal.

The center will bear Blair's name as "a lasting tribute to honor a man who has been a friend to so many," said committee chairman William C. Latham.

Blair helped start the 4-H program in Northern Virginia and has been active in the program for many years. He says he enjoys watching children from both the farms and suburbs learn more about growing produce and raising animals.

"Farming is rewarding but it's difficult," he said, recalling years of devastatingly dry summers and epidemics that wiped out whole herds of livestock.

Then, he said, Fairfax was a close and happy community when dairy cattle were more prevalent than federal workers.

"I'm not sad to see the development, the houses," he said. "We saw it coming because we were close to a growing metropolitan center. The farmers have gotten a good price for their land, so there is no tragedy here."

In 1972 Blair moved from already suburban Fairfax to then more rural Prince William County. The development of houses and businesses has been right at his heels, though.

"Farmers here are selling out just like they sold out in Fairfax 20 years ago," he said. "In another 20 years we'll have another Fairfax right here in Prince William."

However, the technology Blair helped bring to farmers over the years allows the average farm to produce four times as much now as it did 30 years ago. Blair said better diets for dairy cows has helped double their milking capacity and modern farming techniques allow the United States to provide more food on fewer and fewer acres.

"That's the greatest reward, seeing that all that information I was trotting out to the farmers actually worked," he said. "Standing in a field and seeing the crops thick or the livestock healthy . . . what a feeling to stand there and see that."

For Blair, who owns the farm he grew up on in Pittsylvania County, the era of farming in Northern Virginia is not over.

"There are still farmers in Fairfax and Prince William who need to be supported by everyone in the community. And there are still children who have to learn that milk comes from a cow. All the development in the world won't change that."