In 1924, a prominent grain exporter speaking before the American Farm Bureau Federation in Chicago predicted a limited future for farming, saying that people could eat only so much food. "Unfortunately, the human stomach is not elastic," the speaker said.

Wheeler McMillen, then an editor for Farm and Fireside magazine, disagreed, and has continued to disagree ever since. For the last 60 years, McMillen has spent much of his time telling people that even if food was plentiful for all people, agriculture remains an industry with a barely tapped potential.

Consider, he says, that the common milkweed and goldenrod may prove to be a valuable source of industrial rubber.

This idea and many others have been researched, in part, because of McMillen's lifelong efforts, which last month won him a presidential award, signed by President Reagan Oct. 11, "in recognition of his immense contributions to American agriculture through his initiative and promotion of new uses for farm crops."

McMillen, who lives in Loudoun County, received the award at a luncheon attended by 175 scientists and industry representatives that kicked off U.S. Secretary of Agriculture John R. Block's two day "challenge forum" on new uses for farm products.

Among other accomplishments (such as 15 books, so far, on farming and other subjects), McMillen helped establish the Farm Chemurgic Council, which researched the development of new industrial uses for farm products and new markets for farmers.

A result of the council's work, which McMillen directed from 1937 to 1962, was funding in the late 1930s for four U.S. Department of Agriculture research laboratories. From these labs came developments such as a quick, large scale method of producing penicillin (utilized during World War II), dehydrated foods, juice concentrate and wash-and-wear cotton.

The Farm Chemurgic Council, another of McMillen's efforts to promote new uses for farm products, had its beginnings in Chicago, when McMillen heard the speech about the human stomach.

"I got to thinking about that," McMillen said recently. "No matter how rich you get, you eat only three meals a day. But you might have two houses, four automobiles, and half a dozen TVs. . . . Why couldn't farmers grow things for other than meals?"

Since then, "I have tried to advance the idea that instead of paying farmers not to grow, not to produce, we should concentrate on developing, new non-food uses, or better food uses, and new kinds of crops that would displace the excess of those that we now have."

"All I've done is talk about it, and write about it, and get people interested."

McMillen, who once said he "came from a cornfield and a hog lot and sat down at a desk in New York," grew up on a farm in Ohio, which he left the first time for college and then jobs, including reporter, editor and publisher, at newspapers in Ohio, Indiana and Illinois.

He went back to farming the family place for another four years before leaving in 1922 for New York City. There he was editor of Farm and Fireside (later renamed Country Home), leaving in 1939 to join the staff of Farm Journal magazine, where he remained as editor in chief until 1963. A popular public speaker, McMillen addressed farming industry groups across the country at least once a week during his years with Farm Journal.

Since 1979, he has shared a home near Lovettsville with his son, Robert McMillen, a former special assistant to the U.S. Secretary of Agriculture.

The 10-acre property on which they live was "once cow pasture," said McMillen, looking out the large windows toward the 2,500 white pines he and his son planted. There's also a stand of black walnut, and a pond, which leaks. "I'm hoping to get someone to put in a hydraulic pump from the creek to the pond," said McMillen, relighting a cigar while his two black poodles vied for positions on his lap.

"We spend part of every day this way," he said, referring to the company on his lap.

At other times, if he's not observing various birds at war over a large birdhouse originally intended for purple martins, McMillen usually is sitting at the electric typewriter he bought himself last January for his 91st birthday, puffing away on a cigar and finishing the last chapter of his 16th book.

Tentatively titled "Nine Decades in the Human Race," the book "is in a sense autobiographical," he said. "I've tried to make it not what some would call auto-brag-biography." It is mostly "pleasant memories I have and a few opinions."

McMillen smiles when asked for his reaction to receiving the recent award. "I thought it was a nice and thoroughly appreciated compliment and it sort of swelled my head a little bit, but I've gotten over that. It's helpful, one of those tools that calls attention to the ideas I'm trying to sell."

One of McMillen's major premises, which he has explored to the greatest extent in his most recent book, "Feeding Multitudes," a history of how farmers made America rich, is that "farmers are the only people in the world that the human race cannot do without. It's certainly true, because we've got to eat and we can't eat without them."

Two things about Wheeler McMillen won't change. He'll keep on writing (he's planning a book about the Golden Rule, which, he said, is his only religion), and he'll keep on smoking cigars.

"I don't really smoke an awful lot," he said. "I never smoke more than one cigar at a time. I only started smoking cigars when I was 15. I like to say that I've thought about quitting, but I've had the willpower to keep going."