Evaluation of Nitrogen Rates on Edamame.

In 2012, large-scale production of edamame [Glycine max (L.) Merr.] was introduced into Arkansas.  Due to the lack of fertility recommendations for edamame production, research was conducted to evaluate the response of nitrogen sources and rates.  The goal of the study was to determine if added N would produce a higher yield, increase seed number, increase seed size, and improve overall quality of the edible soybean.  Research plots were established at two locations in Arkansas with four replication of each treatment in a randomized complete block arrangement.  Two varieties were tested with applications of 28 kg/ha of N applied at preplant, V6, R1 and/or R3. Nitrogen sources tested were Ammonium Sulfate and Urea with Agrotain. Plots were mechanically harvested and fresh weight yield was determined.  Sub-samples were evaluated for quality and pod fill.  The pods were classified by number of beans per pod (3 bean, 2 bean, and other), weighed and sorted per variety and treatment.  Data showed no significant difference between the treatments and the untreated check in fresh-weight yield, seed size, or pod fill within each variety. However, differences were seen between the two varieties among the treatments.  The variety more adapted to the climate and growing season in Arkansas showed an increase in pod fill and fresh-weight yield, but it lacks the seed size of the preferred edamame soybean.  These results show no economical or quality advantage to applying added nitrogen for edamame production.