At What Time of the Year Do You Plant Soybeans?

Soil Conditions

• Soybean seed is rather finicky in its soil needs in order to both germinate and for the emerging roots and shoots to penetrate through the soil profile. A crumbly, loose-textured soil needs to be evenly moist and at least 60 degrees Fahrenheit at the 2-inch depth. Plant seeds 1 to 1 1/2 inches deep. Dry soil inhibits germination and wet, soggy soils inhibit aeration among soil particles, suffocates seed embryos and encourages fungal diseases.

Seasonal Timing

• Soybeans take at least 85 days from germination to production of the first tender, green seed pods. More time is needed for the pods to fully develop and dry completely with dry, hard seed inside. In the United States, regardless of latitude, plant soybeans in May or June when soil temperatures are adequately warm and no frost occurs. This takes advantage of the long photoperiod of summer that triggers soybean flowering; soybeans planted in late summer to winter will not bloom well because the days are too short. Day length also affects how long the seed pods take to develop on plants; shortening days hastens seed development.

Plant Growth Insight

• Soybean seeds still germinate at other times of year, regardless of day length, if soil conditions are adequate. However, warm, humid weather will hasten the bean plant's growth of leaves and stems. Soybeans planted in frost-free conditions in late summer or fall will likely not flower and produce seed pods, but the vegetative growth may be used as a cover crop or as forage for animals.

Double Cropping

• In the southern U.S., or in subtropical regions with very long growing seasons with no frost, a double crop of soybeans may be planted each year, albeit challenging. Because of the need for warmth and long days, the first sowing of soybeans must occur by the end of March. These plants' pods are harvested by late June, and another sowing of the field occurs as early in July as possible, even better if it is still June. Overall, soybeans sown in May or June grow the best and flower and set seed pods most readily. One soybean crop a year is easiest.