If you should happen to stray from busy Route 1 in Beltsville, any nice Saturday or Sunday in the fall you may chance upon a scene out of another time and place.

In the middle of fields that appear to be at least half weeds, sleeping babies lie comfortably in carrying pouches or in baskets on the ground. Little children shout and play in the sand. Women and older children sit or squat on the ground, trimming roots and leaves off plants, stacking them in large plastic bags or baskets. The digging and harvesting have been left to the men.

What you have stumbled upon is a pick-your-own Oriental vegetable farm, one of four in the Washington area owned by a Korean food technologist, Byong Yoo. Sometimes in late September the vegetables are ready for harvesting: two kinds of white radishes, one known to the Japanese as daikon; three kinds of Chinese cabbage including the most familiar, bok choy; mustard greens; two varieties of edible chrysanthemums: hot red and green peppers and the very pungent Chinese parsley, which Latin American cooks call cilantro.

Most of Yoo's customers are Oriental. The few Americans who come are either married to Orientals or have taken Chinese cooking classes. Anyone else would be at a loss for what to do with most of the vegetables once they were harvested, if indeed, they knew how or when to pick them. Only the bok choy and the cabbage called napa are likely to be found in the ordinary supermarket.

Surprisingly, Washington has a large enough Oriental population to support the four farms. (The others are in Chantilly, Landover and Potomac. All are open on weekends; some are open from 5 to 7 p.m. during the week. For more complete information and directions for reaching the farms, call Dr. Yoo at 572-4747.)

While a few Chinese restaurants buy from the farms, most customers are individual families who harvest enough for at least a week. But one Korean from Cleveland drove 10 hours in a pick up truck, slept in his truck, picked "a couple of thousand pounds of vegetables in 12 hours" according to Yoo, and then turned around and drove back to Cleveland.

Last week the radishes, cabbages and mustard greens were 20 cents per pound; the crysanthemums and Chinese parsley 50 cents per pound; the peppers 99 cents.

Here are some general directions for using the different vegetables grown on the farms.

Chinese cabbages: Bok choy is tender-crisp, sweet and very mild. Stir-fry it alone or with meat or cook it in soup.

Napa is crisp with a delicate flavor. It can be served raw or cooked, plain or in soups. It can be pickled either alone or with other vegetables. It is just as good as ordinary cabbage with corned beef.

Green cabbage has a stronger flavor and firmer texture but can be used in the same way as napa cabbage.

Mustard greens: Less pungent than American mustard greens. Stir-fry and sprinkle with Chinese parsley or toasted sesame seeds. Good, too, steamed or in soups.

Radishes: Both varieties, the Korean or Chinese and the Japanese (daikon) are milder than our red radish. The Koreans pickle it and call it kimchee. The Japanese make cucumber pickle out of daikon. Both kinds can be eaten raw, thinly sliced into salads. They can be grated as a garnish for other vegetables and soups.

Edible crysanthemum is cooked and served with bean curd in a soy sauce and seasame oil dressing.

Chinese parsley comes from the coriander plant. It is a wonderful garnish for any Oriental or Mexican speciality and is often found in the spicy Mexican salsa made of fresh chopped tomatoes and onions.

Peppers are the fiery kind, with the red considered the hotter of the two. Hot peppers are used in Szechuan cooking particularly. STIR-FRIED CHINESE GREENS (4 servings) 6 cups Chinese greens cut into 2 inch strips about 1/2 inch to 1 inch wide 2 tablespoons vegetable oil, peanut preferred 1 clove garlic, minced or pressed

Heat the oil in a wok or large frying pan over high heat. When oil is hot add garlic and ribs or stem pieces. Cook, stirring until pieces are coated with oil. Add 1/4 cup water. Cover and cook 2 to 4 minutes, or until barely tender. If using leaves, add them and cook about 1 minute longer until leaves are not quite wilted. GREEN AND BEEF (2 to 3 servings) 3/4 pound lean boneless beef cut in 1 by 3-inch strips 1 tablespoon soy sauce 3/4 cup chicken broth 4 taspoons cornstarch 2 teaspoons soy sauce 1 teaspon minced fresh ginger 2 tablespoons dry sherry 6 cups cut-up Chinese greens 2 tablespoons oil Mix meat with 1 tablespoon soy sauce. Mix cornstarch with broth. Stir in remaining soy sauce, ginger and sherry. Cook the greens as directed in recipe above; remove from pan. Add oil to the pan and place over high heat. When oil is hot add meat and cook, stirring, until meat is lightly browned, about 4 minutes. Return vegetables to pan and add broth mixture. Cook and stir only until sauce thickens. CHINESE GREENS SOUP (6 servings) 6 cups cut-up fresh Chinese greens 3/4 pound boneless pork cut into 2-inch long strips 1 tablespoon soy sauce 1 clove garlic 6 cups chicken broth Salt and pepper to taste

Mix pork with soy sauce and garlic. Bring broth to boil. Add pork mixture; cover and simmer until pork is tender, about 10 minutes. Add stem and rib pieces of greens; bring to boil, simmer, uncovered, 2 minutes longer or until pieces are barely tender. If using leaves, add them and simmer one minute longer or until they are just wilted. Season to taste with salt and pepper. WHITE RADISH AND CARROT SALAD (8 servings) 3/4 pound daikon (white radish) 1 medium-sized carrot Salt 6 tablespoons rice wine vinegar 2 tablespoons sugar

Peel the radish and cut into 2-inch julienne strips. Scrape carrot and cut into the same size julienne strips. Place vegetables in bowl and sprinkle with a little salt; mix gently for about a minute. Set aside for 3 minutes then squeeze out through sieve; set aside to drain. In another bowl combine vinegar, sugar and salt to taste. Add thoroughly drained vegetables. Mix lightly, cover and refrigerate until ready to use. Will keep a week.