Soybeans are legumes, native to East Asia, that are grown for oil and protein around the world. Cultivated primarily in warm and hot climates, soybeans were originally used as nitrogen fixers in early systems of crop rotation – ancient farmers would plant a field of soybeans on an exhausted or depleted field and then plow the crop under to replenish the soil. Development of use technologies such as fermentation and processing for oil has led to many new applications of this useful plant. This article will discuss the origin and development of the soybean, its cultivation and usage, and the crop’s important role in the world economy.

Taxonomy and Natural History

Soybeans are native to East Asia, where they appear to have been cultivated from a wild species known as glycine soja starting about 5,000 years ago. The semi-legendary Emperor Shennong, the “Divine Farmer” who is believed to have introduced agriculture to the peoples of China and Vietnam, is said to have listed soybeans as one of the “Five Sacred Plants,” a list that also includes rice, wheat, barley and millet. Soybeans were also cultivated in Korea no later than 1000 BC, and in Japan from the time of the Roman Empire.

Soy belongs to the fabaceae or leguminosae (legume) family which also includes peanuts, chickpeas and other beans and pulses. This constitutes the third largest family of flowering plants, with well over 19,000 distinct species. Soybeans themselves are hard and rounded, and range in color from black to pale yellow.  Although classified as a bean, a soybean is actually an oilseed like the peanut. Because of their high oil and protein content, soybeans are particularly useful for a variety of purposes.

Soybeans were introduced to Europe and the United States from colonial times. However, the plant was not cultivated in significant amounts outside of Asia until 1910. Since then, the balance of production has shifted; 55% of the world soybean crop is harvested in the Americas.

Soybeans are primarily consumed by humans after being fermented and turned into a curd. Tofu, a bland, cheese-like substance made from the whey of fermented soybeans, is the most common example of this type of soybean application. Once known as the “Cow of the Orient,” the soybean is about 40% protein, 35% carbohydrate, 20% fatty oil and 5% ash. It is one of the few plants that provide a complete protein, and is therefore often used as a substitute for meat and dairy products. Some food companies such as Morningstar Farms produce simulated bacon, sausage and hamburger from soy with taste and texture that is remarkably similar to the real thing. Because soy protein is quite stable at high temperatures, it is particularly suited to wok cooking and is a staple of many Chinese, Korean, Japanese and Southeast Asian dishes. Another common food use is in milk substitutes, such as soy milk. It was once thought that these applications were primarily modern, but words such as “soy milk” are at least 2000 years old and it is likely that such uses are in fact quite ancient.

Soybeans are highly versatile, and the beans can be processed into oil, flour, and meal. Each of these forms has many dietary uses, and soy is one of the more dietarily versatile legumes.

In the U.S., soybeans are a chief source of vegetable oil. Because the oil is extracted with the use of the hydrocarbon chemical hexane and is usually hydrogenated in order to create semi-solid shortening, several sources have raised health concerns. Another concern, although one with less scientific grounding, is the production of genetically-modified soy. These GMO beans have been created in order to allow farmers to use certain pesticides, such as Roundup®, without causing harm to the plant itself. This advantage is such a enormous incentive to farmers that the proportion of genetically modified soybeans has jumped from about 8% in 1997 to 89% by 2006. Some concern has been raised about preserving the diversity of the soybean genome, but Roundup modification has been added to nearly all strains, leading to a relatively steady level of genetic diversity in the species.

There are many claims about the health benefits of soy consumption; some scientists say that the isoflavones in soy help to prevent cancer, and the U.S. Food and Drug Administration recently approved health claims that soy consumption can lower cholesterol levels. However, another study showed that raw soybean flour induced pancreatic cancer in laboratory rats, although these rats were fed amounts far in excess of that which normal humans would normally ingest. Additionally, there have been no studies linking soy consumption and pancreatic cancer in humans, who do not normally eat uncooked flour in any event.

Some owners of diesel-powered vehicles have been fueling their cars with used, filtered soybean oil. However, in order to do this, modifications must be made to the fuel system so that the oil does not congeal under cold temperatures. Soybean oil when applied to the skin as also been shown to be effective at repelling mosquitoes and other insect pests.

Soybean Production

The U.S. has been the largest producer of soybeans, followed by Brazil. However, soybean production has been falling in the U.S. recently, a trend which may continue in spite of the increasing demand for soybeans, owing to competing demands for arable lands as pressure on food crops increases. In 2005, there was a total of 214.3 metric tons of soybeans harvested, over a third of which came from the U.S. This is expected to reach 280 metric tons in the next decade as the demand for biofuels increases. Most US soybeans are actually raised for export.

Soybeans grow best in temperatures between 68 and 86 degrees Fahrenheit, and can grow in a wide range of soil types. The plant is susceptible to a number of bacterial diseases, including blight and wilt. Modern plants reach a height of about 1 meter, and take between 80 and 120 days from planting to harvest.