Soybean
The soybean, soy bean, or soya bean is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed.
Soy is a key source of food, useful both for its protein and oil content. Soybean oil is widely used in cooking, as well as in industry. Traditional unfermented food uses of soybeans include edamame, as well as soy milk, from which tofu and tofu skin are made. Fermented soy foods include soy sauce, fermented bean paste, nattō, and tempeh. Fat-free soybean meal is a significant and cheap source of protein for animal feeds and many packaged meals. For example, soybean products, such as textured vegetable protein, are ingredients in many meat and dairy substitutes. Soy-based foods are traditionally associated with East Asian cuisines, and still constitute a major part of East Asian diets, but processed soy products are increasingly used in Western cuisines.
Soy was domesticated from the wild soybean in north-central China between 6,000 and 9,000 years ago. Brazil and the United States lead the world in modern soy production. The majority of soybeans are genetically modified, usually for either insect, herbicide, or drought resistance. Three-quarters of soy is used to feed livestock, which in turn go to feed humans. Increasing demand for meat has substantially increased soy production since the 1980s, and contributed to deforestation in the Amazon.
Soybeans contain significant amounts of phytic acid, dietary minerals and B vitamins. Soy may reduce the risk of cancer and heart disease. Some people are allergic to soy. Soy is a complete protein and therefore important in the diets of many vegetarians and vegans. The association of soy with vegans and the misconception that soy increases estrogen production have led to "soy boy" being used as a derogatory term.
Etymology
The word "soy" derives from the Japanese soi, a Kagoshima dialect variant of shōyu, which in turn comes from the Chinese jiangyou, meaning "soy sauce".The name of the genus, Glycine, comes from Linnaeus. When naming the genus, Linnaeus observed that one of the species formerly within the genus, which has since been reclassified to the genus Apios, had a sweet root. Based on the sweetness, the Greek word for sweet, glykós, was Latinized. The genus name is not related to the amino acid glycine.
Description
Like most plants, soybeans grow in distinct morphological stages as they develop from seeds into fully mature plants.Germination
The first stage of growth is germination, a method which first becomes apparent as a seed's radicle emerges. This is the first stage of root growth and occurs within the first 48 hours under ideal growing conditions. The first photosynthetic structures, the cotyledons, develop from the hypocotyl, the first plant structure to emerge from the soil. These cotyledons both act as leaves and as a source of nutrients for the immature plant, providing the seedling nutrition for its first 7 to 10 days.Maturation
The first true leaves develop as a pair of single blades. Subsequent to this first pair, mature nodes form compound leaves with three blades. Mature trifoliolate leaves, having three to four leaflets per leaf, are often between long and broad. Under ideal conditions, stem growth continues, producing new nodes every four days. Before flowering, roots can grow per day. If rhizobia are present, root nodulation begins by the time the third node appears. Nodulation typically continues for 8 weeks before the symbiotic infection process stabilizes. The final characteristics of a soybean plant are variable, with factors such as genetics, soil quality, and climate affecting its form; however, fully mature soybean plants are generally between in height and have rooting depths between.Flowering
Flowering is triggered by day length, often beginning once days become shorter than 12.8 hours. This trait is highly variable however, with different varieties reacting differently to changing day length. Soybeans form inconspicuous, self-fertile flowers which are borne in the axil of the leaf and are white, pink or purple. Though they do not require pollination, they are attractive to bees, because they produce nectar that is high in sugar content. Depending on the soybean variety, node growth may cease once flowering begins. Strains that continue nodal development after flowering are termed "indeterminates" and are best suited to climates with longer growing seasons. Often soybeans drop their leaves before the seeds are fully mature.The fruit is a hairy pod that grows in clusters of three to five, each pod is long and usually contains two to four seeds 5–11 mm in diameter. Soybean seeds come in a wide variety of sizes and hull colors such as black, brown, yellow, and green. Variegated and bicolored seed coats are also common.
Seed resilience
The hull of the mature bean is hard, water-resistant, and protects the cotyledon and hypocotyl from damage. If the seed coat is cracked, the seed will not germinate. The scar, visible on the seed coat, is called the hilum and at one end of the hilum is the micropyle, or small opening in the seed coat which can allow the absorption of water for sprouting.Some seeds such as soybeans containing very high levels of protein can undergo desiccation, yet survive and revive after water absorption. A. Carl Leopold began studying this capability at the Boyce Thompson Institute for Plant Research at Cornell University in the mid-1980s. He found soybeans and corn to have a range of soluble carbohydrates protecting the seed's cell viability. Patents were awarded to him in the early 1990s on techniques for protecting biological membranes and proteins in the dry state.
Chemistry
Dry soybeans contain 36% protein and 20% fat in form of soybean oil by weight. The remainder consists of 30% carbohydrates, 9% water and 5% ash.Soybeans comprise approximately 8% seed coat or hull, 90% cotyledons and 2% hypocotyl axis or germ.
Taxonomy
The genus Glycine may be divided into two subgenera, Glycine and Soja. The subgenus Soja includes the cultivated soybean, G. max, and the wild soybean, treated either as a separate species G. soja, or as the subspecies G. max subsp. soja. The cultivated and wild soybeans are annuals. The wild soybean is native to China, Japan, Korea and Russia. The subgenus Glycine consists of at least 25 wild perennial species: for example, G. canescens and G. tomentella, both found in Australia and Papua New Guinea. Perennial soybean belongs to a different genus. It originated in Africa and is now a widespread pasture crop in the tropics.Like some other crops of long domestication, the relationship of the modern soybean to wild-growing species can no longer be traced with any degree of certainty. It is a cultigen with a very large number of cultivars.
Subspecies
, Plants of the World Online accepted the following subspecies:- Glycine max subsp. formosana Tateishi & H.Ohashi
- Glycine max nothosubsp. gracilis H.Ohashi = G. max subsp. max × G. max subsp. soja
- Glycine max subsp. max
- Glycine max subsp. soja H.Ohashi
Ecology
Cultivation
Soybeans are globally important agricultural crops, grown as a major source of protein and oil. It prefers fertile, well-drained soils and requires a warm temperate climate with adequate rainfall or irrigation. Soybeans are mainly grown in the United States, Brazil, and Argentina.It is usually planted in straight rows using modern machinery, and pests and weeds must be controlled to maintain the crop. After maturity, it is harvested using mechanized harvesting machines. Soybeans are used in the production of many food and industrial products, such as tofu, oils, and feed, in addition to their role in improving soil fertility by fixing nitrogen.
Conditions
Cultivation is successful in climates with hot summers, with optimum growing conditions in mean temperatures of ; temperatures of below and over stunt growth significantly. They can grow in a wide range of soils, with optimum growth in moist alluvial soils with good organic content. Soybeans, like most legumes, perform nitrogen fixation by establishing a symbiotic relationship with the bacterium Bradyrhizobium japonicum. This ability to fix nitrogen allows farmers to reduce nitrogen fertilizer use and increase yields when growing other crops in rotation with soy. There may be some trade-offs, however, in the long-term abundance of organic material in soils where soy and other crops are grown in rotation. For best results, though, an inoculum of the correct strain of bacteria should be mixed with the soybean seed before planting. Modern crop cultivars generally reach a height of around, and take 80–120 days from sowing to harvesting.Soils
Soil scientists Edson Lobato, Andrew McClung, and Alysson Paolinelli were awarded the 2006 World Food Prize for transforming the ecologically biodiverse savannah of the Cerrado region of Brazil into highly productive cropland that could grow profitable soybeans.Contamination concerns
Human sewage sludge can be used as fertilizer to grow soybeans. Soybeans grown in sewage sludge likely contain elevated concentrations of metals.Pests
Soybean plants are vulnerable to a wide range of bacterial diseases, fungal diseases, viral diseases, and parasites.The primary bacterial diseases include bacterial blight, bacterial pustule and downy mildew affecting the soybean plant.
The Japanese beetle poses a significant threat to agricultural crops, including soybeans, due to its voracious feeding habits. Found commonly in both urban and suburban areas, these beetles are frequently observed in agricultural landscapes where they can cause considerable damage to crops like corn, soybeans, and various fruits.
Soybean cyst nematode is the worst pest of soybean in the US. Losses of 30% or 40% are common even without symptoms.
The corn earworm moth and bollworm is a common and destructive pest of soybean growth in Virginia.
Soybeans are consumed by whitetail deer which may damage soybean plants through feeding, trampling and bedding, reducing crop yields by as much as 15%. Groundhogs are also a common pest in soybean fields, living in burrows underground and feeding nearby. One den of groundhogs can consume a tenth to a quarter of an acre of soybeans. Chemical repellents or firearms are effective for controlling pests in soybean fields.
Soybeans suffer from the fungus Pythium spinosum in Arkansas and Indiana, and China.
In Japan and the United States, the Soybean dwarf virus causes a disease in soybeans and is transmitted by aphids.