How Do Soybeans Grow?

 

USDA hardiness zones 8-11

 

The soybean is a warm weather plant in the legume family, native to eastern Asia. 

The soybean is a bush bean that does not require staking, and, depending on the variety, can grow from 1 to 3 feet tall. Leaves on the soybean plant are hairy and the flowers produced are white with lavender shading. Pods grow in clusters of 3 to 5, and each contains 2 to 4 seeds. Seeds are as small as a pea or as large as a kidney bean, depending on the variety grown. There are more than 10,000 soybean cultivars.

 

Seasonal Growth

 

Health Benefits

​

In recent years, the soybean has become perhaps the most controversial member of the legume family, due to the mixed opinions and research surrounding its nutritional benefits and risks. It is worth noting that soybean oil and soy protein have found their way into a great deal of refined and processed foods currently produced in the United States. Refined products such as soybean oil and soy protein should be avoided. However, when consumed in an un-processed state, the soybean has terrific health benefits.

 

The soybean is a nutrient-rich alternative to meat. 

 

Mature, boiled, whole soybeans contain large amounts of vitamins B1, B2 and B6, vitamin K, iron, calcium, manganese, selenium, potassium, phosphorus, copper and magnesium. 

 

Just one cup of soybeans contains 68 grams of protein and 17 grams of dietary fiber. Most plant proteins are considered “incomplete” because they lack one or more of the essential amino acids. The soybean is not only higher in protein than all other legumes, but it is the only plant source of complete proteins, which contain nine essential amino acids. 

 

The soluble fiber in soybeans helps to promote digestive health by adding bulk to stools and helping waste pass quickly through the digestive tract. A fiber-high diet can help prevent constipation, as well as colon cancer, diverticular disease and hemorrhoids. 

 

The high concentration of calcium in soybeans is crucial to bone and dental health. The isoflavones in soybeans are reported to help increase bone density in women and decrease their risk for osteoporosis. Isoflavones are a chemically very similar to estrogen, and during menopause will bind to estrogen receptors, easing the severity of symptoms such as hot flashes. Although studies have not indicated that a diet high in isoflavones found in soy contributes to breast cancer in humans, animal research results have been mixed. 

 

Soybeans contain approximately 63% polyunsaturated fats, including Omega-3 fatty acids. The soybean is one of few plants that contains Omega-3 fatty acid, which is an essential nutrient that lowers the risk for heart disease, alleviates joint pain, and decreases the symptoms of depression.

 

In the form of fermented products such as miso, tempeh and soy yogurt, the soybean serves as an excellent probiotic. 

 

History

​

Soybeans originated in southeast Asia and were first domesticated in China, although the date of the plant’s first cultivation is unknown. According to myth, China’s legendary Emperor Shennong declared the soybean plant as one of the “five sacred plants” in China circa 2800 BCE, and recent research indicates that wild forms of soybean were in evidence before recorded history (prior to 5,000 BCE).

 

Some scholars suggest that farmers began to cultivate soybeans in China around 3500 BCE. The oldest preserved soybeans that resemble modern varieties were found in Korea, dating to approximately 1000 BCE. 

 

From the first century CE through the Age of Discovery in the 15th and 16th centuries, the soybean plant farming spread throughout Asia. It made its way to the North American colonies in 1765, where it was used primarily as forage for livestock. It was not until the early 20th century that soybeans were recognized in the western world as a nutritious food for human consumption. 

 

In 1904, American chemist, George Washington Carver, discovered soybeans are a valuable source of protein and oil, and they could also be grown to promote soil quality for rotating cotton crops.  

 

In 1919, William Morse co-founded and became the first president of the American Soybean Association, and brought more than 10,000 soybean varieties from China to the United States. 

 

Interestingly, scientists in Henry Ford’s labs discovered a method that produced “soybean plastic” for gear shift knobs, window casings, accelerator pedals and other automobile parts. By 1935, the Ford factory was using one bushel of soybeans per car manufactured. 

 

The increased demand for oils, lubricants and plastics during World War II demanded greater soybean production in the United States in the 1940s. In the 1950s, Americans began to consume ever larger amount of meat, and soybean meal became farmers’ affordable, protein-rich livestock feed of choice. In the 1960s, the United States was responsible for 90% of the world’s soybean exports.

 

By the first decade of the new millennium, the United States still led the world in soybean production, responsible for 32% in 2007. As of 2014, the United States remains among the top five countries responsible for 90% of the world’s soybean production.

 

Propagation

 

Soybeans thrive in warm climates where daytime temperatures average 70 degrees Fahrenheit, and prefers loose, well-drained soil rich in organic matter. In warm weather regions, soybeans are planted in late winter, however, in colder zones, it is planted 2 to 3 weeks after the last freeze, as soybeans are not frost tolerant.

 

Soybeans are easily grown from seeds.  They germinate quickly, their vegetative growth phase continues for six to eight weeks after the seedling emerges. One or two weeks after flowers appear, the first seed pods emerge. The pods take approximately 30 to 40 days to mature before they are ready to harvest.

 

Harvesting

 

Green shell beans (used to make the popular Japanese soybean snack, edamame), are harvested when the soybeans are about half mature, approximately 85 days after sowing. The best way to test for peak ripeness is by appearance and taste. A green soybean pod should be about 3 inches in length, with the beans plump and firm in the fuzzy shell. The leaves on the plant may be beginning to turn a yellowish green. There is a 10 day window for harvest before the beans are too dry - then they are then left on the plant to harvest as dried beans. 

 

**Never eat soybeans raw. They are toxic to humans when consumed raw.**

 

To taste-test soybeans for ripeness, pick a few pods and place them in a pot of boiling water for five minutes. Rinse under cold running water to stop the cooking process and cool the beans. Pop the beans out of their pods and taste. If the soybean has a sweet flavor and good texture, the rest of the crop is ready for harvesting. 

 

Storage
 

Washed, uncooked, green shelled or unshelled soybeans keep in the refrigerator for up to 10 days. For longer storage (or for immediate use), soybeans are blanched in boiling water for 2 to 3 minutes.

 

Boiling soybean pods for 2 to 3 minutes also makes them easier to shell by hand. These can be frozen, canned or dried. To freeze, store in an airtight container or plastic Ziploc bag. 

 

To dry soybeans, lay the shelled beans on a cloth or a window screen in the sun for several days to remove excess moisture. When they are hard and do not break open easily, they are dry enough and ready for storage. They can also be dried on a baking sheet in a 160 Fahrenheit degree oven for 60 minutes. If drying in the oven, check soybeans periodically to prevent over-drying. Store in an airtight container in a cool place.

 

Commercial growers use mechanical harvesters.

 

Fun Facts

 

Brazil is the world’s top producer of soybeans, followed by the United States, Argentina, China and India, according to FAOSTAT data from 2012. 

 

Worldwide, approximately 85% of the soybean crop is processed to make soybean meal and vegetable oil, but the myriad uses of the versatile soybean extend much further. 

 

Soy milk, tofu, tempeh, gluten-free soy flour, textured vegetable protein, soy lecithin, and soy sauce are some of the most popular products derived from the soybean.

 

Soybeans and soybean sprouts are  also used in many traditional dishes in China, Japan, Korea and Vietnam. Immature soybeans that are boiled and salted in their shell are known as edamame in Japan. Soybean paste is also a seasoning used in many dishes, including miso. 

​

Grow It Yourself

 

For the purposes of growing edible soybeans at home, green is the best variety to plant because it is the most tender and flavorful, and the easiest to grow. The popular snack, edamame, is derived from green seeded soybeans.  

 

Because the soybean plant cannot tolerate frost, it is important that soybean seeds are planted after the final frost of spring. In warm weather regions that do not run the risk of spring frost, seeds may go in the ground as early as late winter. Soybean seeds require a temperature of at least 55 to 60 degrees to germinate.

 

1.  Dried seeds must be soaked overnight prior to planting. In a garden bed with well-draining, nitrogen-rich soil, sow soybean seeds ½ in deep, two inches apart, in rows spaced approximately two feet apart and in full sunlight. Soybean plants can tolerate light shade, however, inadequate sunlight may reduce their yield. Side dress the rows with fertilizer during planting.

 

2. Water well immediately after planting, and again in 2 to 4 days afterward if there has  been no rain. Soil should be kept moist at all times for optimal growth. Soybeans germinate quickly, developing their first roots within 48 hours of being planted. 

 

3. Seedlings emerge about 5 to 10 days after planting, and grow rapidly upward. Staking is occasionally necessary in instances when the plant becomes so heavy with pods that it drags the stems to the ground. Otherwise, the plant may be left to flourish un-staked.

 

There are black, green, yellow or creamy white seeds, and each is grown for a different purpose. Yellow seeded soybeans, for instance, are used to make bean curd, soy milk, tempeh and tamari. Black soybeans are used to make black bean sauce and soy sauce.