No one doubts that Richard Lyng has the necessary toughness to serve as the new secretary of agriculture. It's the weaknesses he will bring to office that evoke worry.

Little in the background of this 67- year-old Californian suggests that he will have a strong concern for feeding the poor, which is a major USDA obligation -- or was until the recent Republican assaults. Not much in the Lyng record shows that he has sympathies for the small farmer, the black farmer or consumers. In sum, he is exactly the kind of Cabinet member that Ronald Reagan would naturally choose: a white male from the megacorporate world who knows how to keep consumers and the unmonied out of government decision-making and who will keep a heavy boot on the poor and other outsiders.

Lyng is well-regarded as the proverbial insider. He's a chum of Ronald Reagan from the California days. He served the governor in the late 1960s as director of the state's department of agriculture. From 1969 to 1973 he served Richard Nixon in Washington as an assistant secretary for food programs at USDA. Giving the revolving door a free- enterprise shove, Lyng became president from 1973 to 1979 of the American Meat Institute, which represents the $50 billion packing and processing industry. The institute is the lobbying group that promotes the idea that cooked animal corpses laced with antibiotics, chemicals and heart-threatening fat should be on the American table morning, noon and blight.

The Lyng background also includes service on the Agribusiness Advisory Board of the University of Santa Clara, the National Livestock and Meat Board and as codirector of the farm and food division in the Reagan-Bush campaign of 1980. About the only setback in Lyng's career is that he has failed as a promoter of meat with Ronald Reagan. "At breakfast," the president wrote in a 1984 Parade magazine story on "How to Stay Fit," "I pass up the pancakes and sausage in favor of cereal and fruit." Nutrition Action magazine reports that Reagan's family butcher at the California ranch raises cattle without growth hormones or antibiotics.

Since 1981, and with another turn of the revolving door, Lyng has been the No. 2 man at USDA. Those who watch the agency with a steady eye report that it has been he, not Secretary John Block, who has pushed the inner levers and gears that keep things working along Republican Party lines. The pair functioned well. Block was the gentleman farmer who came to Washington as a sincere hard worker with an aw- shucks image of outdoor healthiness. On publicity trips to the Midwest to keep the farmers mollified, Block would put on his boots and John Deere cap and jump the fence to hold piglets for the camera. In Washington, he was a dedicated runner, always in training for the next marathon.

In the summer of 1983, when hunger again became a public issue following $1 billion to $2 billion cuts in the food-stamp program, Block decided to try a poor person's diet. For a week, he and his wife lived on food stamps, which allots an average of less than 50 cents a meal per person. Block found the diet "quite adequate," and then returned to his own.

Richard Lyng, urbane, a member of the Washington Golf and Country Club and accustomed to board-room comforts, is unlikely to pick up piglets, run the Boston marathon or go on food stamps. Until he is confirmed by the Senate, Lyng is declining interviews. That's a loss. He is popular with the media because he is open and accessible.

He cheerfully serves up Grade A quotes. He is best remembered from his Meat Institute days for calling Carol Foreman, a USDA assistant secretary in the Carter administration, "the ayatollah of American agriculture." Foreman's offense was being outspoken in her consumer and public- interest orientation. When Lyng came to USDA under Reagan and after eight years at the Meat Institute, he said that a change had come. The department would have a "producer- farmer orientation." That is likely to continue. One critic of Lyng says that despite his record "you have to like him personally. He plays the game by all the Washington rules. You can call him bad names, but he'll phone you back."

Smoothness is a political asset, one that Lyng's White House friend and boss incarnates. But what of the poor who have been hurt by Lyng's decisions over the years? At USDA under Nixon, he opposed the Women, Infants and Children nutrition program, one that was initiated by Hubert Humphrey. Lyng said WIC wasn't needed. Public-interest groups took the USDA to court to force it to implement the program as Congress passed it. In the past four years, when Lyng and Block were running USDA, 2 million fewer schoolchildren ate school lunches each day than before the cuts in child-nutrition programs.

Hunger and poverty compete for attention with a disastrous farm economy. Lyng, the party loyalist, is likely to hunker down and avoid making any worsening errors as congressional elections approach and growling farmers look to settle scores. Following service to Reagan, Lyng can be expected to go through the door for another revolving.