Vegetable Soybeans

Soybeans are members of the genus Glycine L., which consists of 10 species of mostly viny perennial legumes native primarily in tropical and warm temperate parts of Africa and Asia. The cultivated soybean, Glyine max (L.) Merrill, is the only member of the genus having an erect bushy plant with an annual growth habit. Not known in the wild state, it is thought to be derived, at least in part, from the viny North Asiatic species, Glycine ussuriensis Regel & Maack.

Soybeans first appeared as a cultivated crop in northern China about 3,000 years ago. Although apparently imported to North America at various times during the Colonial era and the early days of the Republic, they did not become a major or crop in the U.S. much before World War II.

For human consumption, soybeans may be eaten either in the immature or mature stages of growth, or in various processed forms.

Adding a dry soybean product to small grain cereals substantially improves protein utilization over the components consumed individually.

Since fresh, immature soybeans are seldom found in either canned or frozen forms on supermarket shelves, they are an excellent vegetable for home gardeners, who may expect yields of 2 bushels of green pods per 100 feet or row. Soybeans have a relatively high protein content for a vegetable and are a good source of vitamin A.

Vegetable soybeans grow best where nights are warm and days not too long. Only very early varieties should be attempted at higher latitudes. They are unlikely to succeed in areas having frost-free growing seasons of less than 130 to 135 days.

Seeds of vegetable soybeans are usually larger than those grown as a field crop, and only a limited number of varieties, such as Fiskeby V and Kanrich, are offered currently by seedsmen. Most vegetable soybeans have yellow seeds, but other colors are known, such as green, black and green, and black and yellow.

Land on which edible soybeans are to be grown should be well prepared before planting. Soybeans do not thrive on strongly acid soils, and liming may be desirable if indicated by soil tests. Because they are legumes, nitrogenous fertilizers are seldom used, but on many soils they will benefit from application of phosphorus and potassium fertilizers (again the gardener should be guided by soil tests).

If soybeans have never been grown on the soil, it may prove wise to inoculate the seeds with nitrogen-fixing bacteria. Rhizobium japonicum is said to be specific for soybeans, and should be available in commercial preparations.

Weed control will be more convenient if the plants are spaced 4 to 6 inches apart, or in hills spaced about 8 inches apart with the rows 30 inches apart. When seeds of varieties differing in maturity are available, better results will ensue if a single planting of these is made rather than successive plantings of a single variety.

Under favorable conditions, edible soybeans will be ready for harvest as immature beans from early varieties about 2 months after planting, while 100 or more days of favorable weather will be needed to mature dry beans.

Soybeans are self-fertile and have mostly self-pollinated flowers. The beans are borne in pods that are produced in clusters of 3 to 15. The pods are slightly curved and hairy, and will average 2 to 3 seeds per pod. In the Orient, the immature pods and seed are eaten together, but this has seldom been done in the United States. When eaten in the immature stage, vegetable soybeans are harvested at about the same maturity as immature lima beans.

If vegetable soybeans are to be eaten as green beans, the pods will shell much easier if they are plunged into boiling water for about 2 minutes, after which the beans can be squeezed from the pods without any difficulty.

If dry mature soybeans are desired, the plants should be cut when the pods are turning brown and windrowed or placed on a rack under shelter until fully matured, when the seeds may be beaten out. This prevents loss through shattering in the garden. Following shelling, dry the seeds thoroughly before storage.

Another way of using edible soybeans is as sprouts (in the same manner as the sprouts of mung beans). Soybeans can be sprouted in any container that has holes in the bottom for drainage and can be covered.

In preparing the sprouts, soak the soybeans overnight and then place them in a container large enough for the beans to swell at least six times their original bulk as they sprout. Cover container to keep out light.

Moisten the beans at least 3 times a day in summer and twice in winter. In winter add warm water and keep the beans in a warm place.

Time to maturity for soybean sprouts is 3 to 5 days in summer and 10 to 15 days in winter. The sprouts are fully grown and ready to be used when 2 to 3 inches long. Once harvested, sprouts should be kept in a cool, humid place.

At least 25 parasitic diseases are common on soybeans in various parts of the United States, variously caused by bacteria, fungi and viruses. In most cases, the best defense is the planting of resistant varieties, or in the case of seed-borne viruses, of virus-free seeds.

In various parts of the United States, soybeans may be attacked by the green clover worm, the thistle caterpillar, the army worm, by leafhoppers, mites, grasshoppers and blister beetles.

Cabbage looper, a major vegetable pest, feeds on soybean leaf.