The Mall, our national lawn, is looking a bit, well, seedy this year.

William F. Ruback, the man in charge of keeping the most walked-upon lawn in the country looking healthy, surveyed the middle of the Mall yesterday near the Smithsonian's Museum of Natural History, where patches of brown earth alternated with the prettier green stuff.

"We didn't do a good job," he said with a sigh. "Once you lose it, it is very hard to get it back."

Ruback, who maintains all of the national park land in downtown Washington with a 100-man National Park Service crew, takes his grass-growing seriously. He has problems no ordinary lawn-lover ever faces, such as 25 million visitors tromping across his grass every year. Then there are the thousands of joggers pummeling the grass every day. And with warm weather come the approximately 30 softball teams that make daily use of the Mall without benefit of permit.

But Ruback, a large, soft-spoken man who has worked for the Park Service for 26 years, is a patient person. Every fall he reseeds the Mall. And every spring, he fills in the bald spots.

This spring, however, earth and seed didn't take to each other as expected, and as a result the Mall is a bit spotty where the National Folklife Festival was held last year.

Yesterday, Ruback decided to give it one more try and seed the area for a third time.

"It is almost too late, but this week we will put down more seed and cover it with a quarter of an inch of dry compost," he said. "If we can keep it damp and keep people off of it, we have a chance of fixing it up."

Ruback said that among his bigger problems are the unauthorized trails beaten into the Mall by joggers and the illegal base paths and home plates carved by ballplayers.

"You have to accept the wear and the tear," he said. "The parks are for people to use. But it is the home plates that are the hardest to fix because they go right back to using them, and the grass never really gets a chance to fill in those spaces."

As for the joggers' trails and the tourists' shortcuts that have created paths between the established walks, Ruback has a different answer.

"We look them all over, and if we are unable to reestablish grass in those areas, we sometimes cover them with macadam and make them official walkways," he said.