Some botanists separate the wild forms of soya from this species and call them Glycine soja Siebold & Zucc.[]. This is the treatment followed here[].

Common Name: Soya Bean

General Information

Glycine max is an erect, much-branched, annual plant that sometimes produces twining stems that climb into the surrounding vegetation. It can grow from 20 - 200cm tall. The deep taproot is branched; up to 2 metres long with lateral roots spreading horizontally to a distance of up to 2.5 metres in the upper 20cm of the soil[].
The soya bean is one of the major staple foods for humans, providing a high quality protein and an edible oil. It is one of the most widely cultivated crops in the world, with a history of cultivation going back to about the 11th century BC. In addition to its seed, the plant has several other edible uses, is commonly used in traditional medicine and its oil has many industrial uses. The plant is also grown as a green manure.

Known Hazards

The raw mature seed contains a range of antinutritional factors; those destroyed by heat are trypsin inhibitors, haemagglutinins, goitrogens, antivitamins, saponins and phytates; heat-stable ones are oestrogens, flatulence factors and lysinoalanine[]. These factors can be removed in several ways - pre-soaking then cooking for several hours in water; sprouting; fermentation to make products such as miso and tempeh; and roasting can all render the seeds wholesome[, ].

Botanical References

,

Range

Originating in E. Asia, it has spread through cultivation.

Habitat

Lowland thickets, C. and S. Japan[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Annual
Height	0.60 m
Pollinators	Insects
Cultivation Status	Cultivated

Cultivation Details

Glycine max is a plant of the subtropics, but its cultivation extends from the tropics to as far north as latitude 52°N[]. It does not grow well in a wet climate[], nor will it withstand excessive heat or severe cold winters[]. If it is to do well in temperate zones the plant requires a hot summer with a mean mid-summer temperature between 16 - 18°c[], followed by a dry autumn[, ]. It grows best in areas where annual daytime temperatures are within the range 20 - 32°c, but can tolerate 10 - 38°c[]. It prefers a mean annual rainfall in the range 600 - 1,500mm, but tolerates 450 - 1,800mm[]. The plant has been reported to tolerate an annual precipitation up to 4,100mm[].
A fairly easily-grown plant, it grows best in a sunny position on fertile, well-drained soils[, ], but does tolerate a wide range of soil conditions[]. Soybeans develop a taproot up to 2 metres long[] and will grow better than many crops on soils that are low in fertility, droughty or poorly drained[]. Prefers a well-drained sandy soil[]. Prefers a slightly acid soil[, ]. Prefers a pH in the range 5.5 - 6.5, tolerating 4.3 - 8.4[, ].
Flowering can commence from 25 - 150 days after germination, depending on daylength, temperature and cultivar[].
Crops can be produced from 10 - 28 weeks after sowing. Average yields of 1,700kg per hectare have been obtained[, ].
High-yielding cultivars, adapted to the locality and grown under proper culture and favourable conditions, will yield more than twice the average yield[].
There are many named varieties[, , ].
The species, and most of its cultivars, is a short-day plant and does not flower or set seed unless the daylight hours are less than 13 hours per day[]. If growing the plant in the temperate zone then it is important to ensure you grow a variety suited to the longer daylight hours.
There are three basic types of soya bean, those with green seeds are considered to be the most tender and best flavoured and are the type best suited for northern climates. Black seeded forms are normally used dried and yellow seeded forms are used for making soya milk, flour etc[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[]. Soybean soils must contain the proper nitrogen-fixing bacteria. When grown on the same land for 2 - 3 successive years, increasing yields are obtained year after year[]. Seed can be purchased that has been treated with this rhizobium, it is unnecessary on soils with a pH below 5.5 but can be helpful on other soils[]. When removing plant remains at the end of the growing season, it is best to only remove the aerial parts of the plant, leaving the roots in the ground to decay and release their nitrogen.

Edible Uses

Mature seed - cooked[, ]. The seeds furnish one of the world's most important sources of oil and protein, they can be eaten as they are in soups, stews etc[, ], though they are also very commonly used in the preparation of various meat substitutes[, ]. The dried seed can be ground into a flour and added to cereal flours or used for making noodles etc[]. The Japanese make a powder from the roasted and ground seed, it is called 'Kinako' and has a nutty flavour and fragrance - it is used in many popular confections[]. The sprouted seed is eaten raw or added to cooked dishes. The toasted seeds can be eaten as a peanut-like snack[]. The seed is also made into numerous fermented foods such as miso and tempeh[] and is also used to make soya milk, a valuable protein supplement in infant feeding which also provides curds and cheese[]. The seed contains 20% oil and 30 - 45% protein[]. All seeds on a soybean plant mature at essentially the same time. Maturity of the seed is accompanied by a rapid dropping of the leaves and drying of the stems[].

The immature seed is cooked and used like peas or eaten raw in salads[, ].

The strongly roasted and ground seeds are used as a coffee substitute[].

The young seedpods are cooked and used like French beans[, ].

An edible semi-drying oil is obtained from the seed[]. It is cooked or can be used as a dressing in salads etc and for manufacture of margarine and shortening[, , ].

Young leaves - raw or cooked[, ].

Medicinal

The fermented seed is weakly diaphoretic and stomachic[]. It is used in the treatment of colds, fevers and headaches, insomnia, irritability and a stuffy sensation in the chest[].

The bruised leaves are applied to snakebite[].

The flowers are used in the treatment of blindness and opacity of the cornea[].

The ashes of the stems are applied to granular haemorrhoids or fungus growths on the anus[].

The immature seedpods are chewed to a pulp and applied to corneal and smallpox ulcers[].

The seed is antidote[]. It is considered to be specific for the healthy functioning of bowels, heart, kidney, liver and stomach[, ].
An ethyl alcohol extract of the plant has shown interesting oestrogenic properties. In addition, it has been shown to reduce cell death from oxidation. The plant has potential as an active ingredient in preparations for the treatment of skin-ageing in post-menopausal women[].

The seed sprouts are constructive, laxative and resolvent[]. They show an oestrogen-like activity in the body and are also antispasmodic[].The sprouts are used in the treatment of oedema, dysuria, chest fullness, decreased perspiration, the initial stages of flu and arthralgia[].

A decoction of the bark or root is astringent[, ].

Soybean diets are valued for treating acidosis[].
Consumption of soya bean is associated with a decreased risk of atherosclerosis and cardiovascular disease, although the exact mechanisms are not clear. There are also indications that soya bean has a positive effect on bone health. The relation between soya bean consumption and reduced risk of cancer is more uncertain[].
Since soybean oil contains a high proportion of unsaturated fatty acids, it is recommended as a part of the diet, along with the seeds of plants such as safflower (Carthamnus tinctorius) and, poppy (Papaver somniferum) to combat hypercholesteremia[].
Commercial grades of natural lecithin, which are often derived from soybean, are reported to contain a potent vasopressor. Medicinally lecithin is indicated as a lipotropic agent[].
Soybean is listed as a major starting material for stigmasterol, once known as an antistiffness factor. Sitosterol, also a soy by-product, has been used to replace diosgenin in some antihypertensive drugs[].

Agroforestry Uses:

The plant is sometimes grown as a green manure[].

Other Uses

The seed contains up to 20% of an edible semi-drying oil[, ]. It is non-drying according to another report[]. This oil has a very wide range of applications and is commonly used in the chemical industry[, ]. The oil is used industrially in the manufacture of paints, linoleum, oilcloth, printing inks, soap, insecticides, and disinfectants[, , , ].

Lecithin phospholipids, obtained as a by-product of the oil industry, are used as a wetting and stabilizing agent in food, cosmetic, pharmaceutical, leather, paint, plastic, soap, and detergent industries[].

Both the meal and the soy bean protein are used in the manufacture of synthetic fibre, adhesives, textile sizing, waterproofing, fire-fighting foam and many other uses[].

The straw can be used to make paper, stiffer than that made from wheat straw[].

The plant is an excellent source of biomass. The oil from the seeds can be used as a diesel fuel whilst the stems can be burnt as a fuel[].

Propagation

Pre-soak the seed for 12 hours in warm water and then sow in early spring in a greenhouse. The seed should germinate within two weeks at a temperature between 12 - 16°c[]. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in late spring or early summer, after the last expected frosts.
Seed can also be pre-soaked for 12 hours in warm water and then sown in situ in late spring, though this will not yield well unless the summer is very hot.