Soybean

Soybean grows readily in most garden soils in full sun, with an optimum soil temperature for germination between 75 and 85°F; seed is typically inoculated with a nitrogen-fixing inoculant labeled for soybeans before sowing.

The plants need regular irrigation but can tolerate brief dry spells once established, and very nitrogen-rich soil should be avoided because it makes the plants lax and hard to manage. Soybean forms root nodules with Bradyrhizobium bacteria, which convert atmospheric nitrogen into a form the plant can use, supplying much of its own nitrogen needs.

Soybean is a short-day, photoperiod-sensitive plant, meaning days must shorten below a critical length before flowering begins; it is grown as a spring-sown crop and can also serve as a summer cover crop.

Soybean is susceptible to numerous pests and diseases, although these are more often an issue on large commercial farms than in the home garden, where growers may not be troubled by them. Among the documented diseases is sudden death syndrome, which causes yield loss across soybean-growing regions of the USA and worldwide.

For fresh eating as edamame, pods are picked while the seeds are plump and the pod is just beginning to lose its fresh green color. For dry beans, pods are left to mature and dry on the plant, with additional drying sometimes needed afterward; full maturity is reached when about 95% of pods show their mature color, after which roughly 5 to 10 days of drying weather are required before the seeds fall below 15% moisture.

Industrial: soybean is grown chiefly for oil and protein. Despite a relatively low oil content of about 20% on a moisture-free basis, it is the largest single source of edible oil and accounts for roughly half of world oilseed production; the meal left after oil extraction carries about 44% protein and is used mainly in animal feed, though the protein in a year's world soybean crop could in principle supply about a third of humanity's food protein needs if consumed directly.

Culinary: soybean is also grown as a vegetable, picked young and eaten as edamame, and it is used as an animal feedstock.

Soybean originated in Eastern Asia, probably in north and central China, with cultivated varieties believed to have spread into Korea and later Japan some 2,000 years ago. It has been grown as a food crop for thousands of years across China and other parts of East and Southeast Asia, where it remains a component of traditional diets, and its native range is described as extending into the Russian Far East.