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The soybean (Glycine max) is a domesticated species in the pea family (Fabaceae). Like other cultivated species in this family, soybean has symbiotic Rhizobium bacteria growing in nodules on its roots. These bacteria fix atmospheric nitrogen gas into ammonia and allow the crop to grow with relatively little additional fertilization of this key nutrient. Soybean is an annual, dicotyledonous plant. It has compound leaves, a bush-like growth form, and whitish or purple, bilaterally symmetric flowers. The bean-like, 2-3 in (5-7 cm) long fruits contain 2-4 hard, round seeds. Depending on the variety, the seeds can be colored black, brown, green, white, or yellow.

Soybean was domesticated in China around 5,000 years ago. Although it has been cultivated in east Asia for thousands of years, it was not commonly grown in Europe or North America until the twentieth century. It is now cultivated worldwide, where conditions permit, and is one of the most useful and most important food crops. In 1999, about 178 million acres (71.9 million ha) of soybean were grown worldwide, and total production was 176 million tons of grain (160 million tonnes).

Soybeans contain as much as 45% protein and 30% carbohydrate. They are used to prepare a wide variety of highly nutritious foods. The beans can be boiled, baked, or eaten as tender sprouts. Soybeans can also be used to manufacture tofu (a soft, cheesy curd), tempe (a soya cake impregnated with a fungus), soy milk (a white liquid preparation), and soy sauce (a black, salty liquid used to flavor). Soybeans are also processed as ingredients for cooking oil, margarine, vegetable shortening, mayonnaise, food supplements (such as lecithin), pharmaceutical preparations, and even paints and plastics. In addition to these many useful products for humans, large amounts of soybeans are fed to livestock.

Bill Freedman

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