THE LIONS, elephants and deer probably don't know it, but they're helping grow their own food at the National Zoo.

The manure they produce is being used in a small pilot vegetable garden on zoo property tended by the Master Gardeners of the D.C. Extension Service.

This is the first year an animal food garden has been attempted.

"If the program proves successful," says zoo horticulturalist Rick Hider, "we may be able to grow some of the food necessary to feed the animals on a regular basis. The Smithsonian owns property out in Front Royal that could be used as gardening plots. It still wouldn't take care of all our food needs, but it would make a sizable dent in it."

Hider helped initiate the garden program in a former zoo parking lot along with zoologist Edwin Gould this spring.

They, in turn, handed over the reins to Allison Brown, coordinator of the Urban Gardening Program, a branch of the D.C. Extension Service and D.C. extension agent Mark Greenleaf. Although only in its sixth month of operation, the urban garden program has literally blossomed around the city, using land along roadsides, in parking lots, and on traffic islands for garden plots -- and now the zoo.

The zoo garden is one of two demonstrations gardens in the District, explains Brown. The other is on Independence Avenue in front of the Air and Space Museum.

The 20-by-40 foot zoo plot is cared for by six volunteer master gardners. They used to have their own seeds and tools -- with some assistance from the extension service (which paid for the hose, for instance) -- to produce a multiple-vegetable garden. Among the vegetables are zucchini, cantaloupe, eggplant, green beans, corn, carrots, pepers, okra, beets, broccoli, cauliflower, tomatoes and sunflowers. Some herbs also are grown, such as basil, sage, thyme and marjoram.

"The garden doesn't nearly approach the needs of the zoo animals. It's about the size a family would need to be well-stocked for a summer," says master gardner Martha Lewis. "I don't know if it's beginners luck, or what, but for a first attempt, the garden is surprisingly good. You know, this land used to be a parking lot, so the soil is only six or so inches deep."

The gardners started tilling soil for the plot in late June, using the zoo's Rototiller. They spaded lime and elephant and deer manure into the soil. Then they planted the seeds. Lion manure was spread along the edge of the plot.

"The smell of the lion manure," notes Lewis, "repels raccoons and other wild animals that might eat the seeds or grown vegetables." (It also repels humans.)

The first thing that strikes you when you see the garden is how brilliantly green it is. "This is due to all the nitrogen in manure," explains Lewis.

Zoologist Gould, who is curator of mammals at the National Zoo, hopes that besides benefiting the animals and being economical for the zoo, the vegetable garden will be educational for the public. "People who visit the zoo will learn about the foods the animals eat and see how vegetables in general are grown.

Gould believes that the zoo garden is an ideal setup, "not because we have better manure than anyone else, we just have more of it."

"Manure," he explains, "improves the quality of the soil by improving the soil's moisture-holding ability. It conditions the soil by adding natural nutrients since it's an organic material and not a chemical."

No pesticides are used in the zoo garden. When the master gardeners run into problems -- like insects or plant diseases -- they take the stricken vegetable to the D.C. Extension Service.

The Master Gardeners Program is run by the extension services of D.C. and Virginia, although it is offered to residents of D.C., Virginia and Maryland.The intensive course consists of 50 hours of gardening lectures, demonstrations and workshops with experts from the land grant universities associated with the extension services (University of the District of Columbia and Virginia Polytechnic Institute). After the course, participants give the extension service 50 volunteer hours, manning extension service phones, working at farmers' markets or visiting urban garden plots. For details on the program call Elizabeth Crowley at 576-7415.

Maryland also offers an independent Master Gardeners program, run by each county. Call your county extension service for details.