Introduction to Soybean
Soybean, an annual, leguminous plant. The soybeanalso called soja and stock peais one of the leading farm crops of the United States. It is grown for food, for use in agriculture, and as a source of raw materials in industry. Throughout the Far East it is known as soja max, and forms an important part of the daily diet.
Soybeans are bushy, upright plants. They grow from one to six feet (30 to 180 cm) in height, depending on the variety of the plant and growing conditions. Short, fine tawny brown or gray hairs cover the entire plantleaves, stems, and pods. Each leaf is composed of three oval leaflets. Small white or purple flowers are borne in clusters which are followed by drooping clusters of brown or yellow pods two to three inches (5 to 7.5 cm) long.
Each pod contains two or three small round seeds, called beans, about the size of an ordinary garden pea. The beans may be yellow, green, brown, or black. Some yellow and some green varieties have black or brown patterns; however, these patterned, or bicolor, beans are not common.
Soybeans are bushy, upright plants with short, fine hairs covering the entire plant.Cultivation
Soybeans are best suited to flat or gently rolling land and require light to heavy rainfall. Soybean crops require growing conditions much the same as those for corn, and for this reason the Corn Belt states of the United States are leading producers of soybeans. In these states, soybeans are mostly grown in rotation with corn. About 100 varieties of soybeans are commonly grown in the United States.
Soybeans are planted at the end of May or in June. They are planted by means of a grain drill, usually in rows, 21 to 24 inches (53 to 60 cm) apart. Soybean plants require a growth period of 75 days for early-maturing varieties, or 200 days for late-maturing varieties. All the bean pods of the plant mature at about the same time and the leaves turn yellow and drop off. Soybeans are harvested with a combine.
Disease-resistant varieties of soybeans have been bred to control the various diseases that attack the plants. Chemical sprays are used to combat such insect pests as grasshoppers, Mexican bean beetles, and velvet-bean caterpillars.
Uses
Soybean crops have many uses in agriculture. They are grown for forage, hay, and silage and for improving soil. Soybeans, like other legumes, add nitrogen to the soil by means of nitrogen-fixing bacteria that live in the nodules, or swellings, on the roots of the plant. These bacteria take gaseous nitrogen from the air and change it into organic nitrogen compounds. The compounds are used by the plant and also are released into the soil, thereby enriching it. Soybeans are sometimes grown as green manure crops. Such crops are plowed under while still green and immature, a practice that adds to the soil humus as well as considerable amounts of nitrogen.
In the United States, the soybean is grown chiefly for its bean, an important source of food for humans and other animals as well as a source of industrial products. The bean contains very little starch, but has a high oil and protein content. About 15 to 22 per cent of the bean is oil and as much as 30 to 40 per cent is protein, about twice as much protein as in any other kind of bean. The soybean is also rich in minerals such as calcium, iron, potassium, and phosphorus. It also contains vitamin A and thiamine, riboflavin, and niacin.
When processed, a bushel of soybeans (60 pounds, or 27.2 kg) yields about 11 pounds (5 kg) of oil and about 47 pounds (21.3 kg) of soybean oil meal. The oil is obtained chiefly by the solvent extraction methodthe beans are crushed, heated, and flaked and then mixed with a solvent (usually hexane) that separates the oil from the flaked beans. Later, the solvent is removed from both the oil and the flaked beans by evaporation and filtration. The flaked beans are called oil cake. They are ground into a fine powder to make soybean oil meal, or soy meal.
The oil is used in margarine and for salad and cooking oils. Industrially, soybean oil is used in the manufacture of such products as paints, enamels, varnishes, printing inks, candles, paste soaps, and rubber.
Soy meal has a number of uses. Without further processing, it is used as livestock feed. When refined into soy flour, it is a valuable ingredient used to increase the protein content of bakery goods, cereal foods, candies, and ground meats such as those used in sausages. Since the soybean contains little or no starch and has a very low sugar content, soybean products are used in dietetic and diabetic foods. In industry, soy meal is used in the manufacture of a wide variety of products, including adhesives, plastics, foaming solutions for fire extinguishers, and fertilizers.
Tofu, or bean curd, a popular health food that is high in fiber and protein, is prepared by boiling soybeans and letting the resulting liquid solidify.
History and Production
The soybean is native to Southeast Asia, where more than 1,000 varieties are grown. Written records reveal that the soybean has been grown in China for more than 4,000 years. Along with rice, wheat, barley, and millet, the soybean was considered one of the five sacred grains of China.
In 1804, soybeans were brought to the United States in sacks as ballast on a ship returning from China. They were first grown as a curiosity and then, for more than 100 years, were chiefly grown as forage and soil-building crops. During the Civil War, however, soybeans were grown as a substitute for coffee beans and at that time were known as the American coffee bean.
In 1898, the U.S. Department of Agriculture encouraged the production of soybeans by introducing many more new varieties from China and Japan. Production increased in the 20th century because of the successful attempts of breeders to develop soybean plants better adapted to North American environmental conditions. Also, farmers learned better ways of growing these crops and industry developed new methods of processing the bean.
The United States was a principal importer of soybean oil and beans until World War II, when it greatly increased its own production to meet shortages of oil and protein food. After World War II, the United States changed its position on the international soybean market from a major importer to a major exporter.
The soybean is Glycine max of the family Leguminosae.