Soy Bean Cultivation

Planting

• According to the National Soybean Research Laboratory, the best time to plant soybeans is early May; however, soybeans require a minimum soil temperature of 55 to 60 degrees Fahrenheit to germinate. Higher temperatures increase germination rates. If soybeans stay under the ground too long, they are more susceptible to diseases. Planting depth is determined by soybean variety, but you should generally plant soybeans from a depth of 1 inch in cool, moist soil to 2 inches in sandy soil.

Nutrients and Soil pH

• Soybeans require nitrogen and receive adequate supplies from nitrogen-fixing bacteria present on the root nodule. Other macronutrients soybeans need include calcium, for root hair growth and cell division; phosphorus for metabolism and photosynthesis; and potassium for regulating water balance. If your soil is low in potassium, add potassium sulfate. Avoid fertilizers containing chloride, as this can injure beneficial soil microbes. Soil pH affects nutrient uptake; soybeans grow best in slightly acid to neutral pH (5.8 to 7.0).

Growth

• Soybeans require three to five months to reach maturity. Plant early-maturing varieties in the north or late-maturing varieties in the south. Soybeans first pass through the vegetative stage, lasting six to eight weeks, when the seedling emerges through the soil. Soybeans produce a taproot that branches off into a fibrous root system. Nodules form on the roots and after 10 to 14 days, nitrogen-fixing bacteria enter the nodules. Soybeans start flowering when they produce six to 10 trifoliate leaves, and one to two weeks thereafter, pods will develop.

Harvesting

• For edamame or green shell soybeans, harvest when the pods are still green and considered about half-mature; these soybeans are usually ready for harvest within 45 to 65 days of sowing. For dry soybeans, harvest when they are not green but yellow and fully mature; these soybeans usually take 100 days from sowing to reach maturity. For dry soybeans, hang them upside down to dry before shelling. For green soybeans, you may need to boil the pods for four to five minutes before shelling.