The Soybean Plant
The soybean (Glycine max) is native to East Asia and has been grown for thousands of years. Soybean plants are on average 3 to 5 feet tall and can have up to 20 nodes. The plant has the ability to produce 600 pods per plant, but on average there are 50 to 100 pods per plant that set seed. Each pod contains on average three seed. Soybean yields are directly dependent on the number of plants per acre, the number of pods per plant, the number of seeds per pod, and the size of the seed.
Soybean varieties are classified based on their requirement to initiate reproductive development and their morphological growth habit. Soybeans are photoperiod sensitive, short-day plants, meaning that days must be shorter than a critical value to induce flowering. Soybean varieties are classified into maturity groups according to their response to photoperiod. Soybean varieties are also classified based on their growth habit. In varieties with a determinate growth habit, the onset of reproductive growth results in the termination of vegetative growth. Indeterminate varieties, however, start flowering several weeks before they terminate vegetative growth. Most Southern varieties are determinate, while most Midwest varieties are indeterminate.
Soybeans are legumes and, like most other legumes, have the ability to supply their own nitrogen. Nitrogen fixation begins with the formation of a nodule on the root. Nodules are produced from Bradyrhizobia bacteria in the soil that invade the root and multiply within the root cells. The soybean plant supplies the bacteria with nutrients and energy, and in return the bacteria convert atmospheric nitrogen (N2) in the air to nitrates (N03-) the plant can then use.
Understanding how soybeans grow and develop is critical to effectively managing the crop for increasing yields.
