Pod Thickness Increase Rate, Relative Pod Thickness and Seed Weight of Edamame (Green Soybeans) at the Optimal Harvest Timing

Abstract

To develop new indices for optimal harvest timing of edamame (green soybeans), pod thickness increase rate, relative pod thickness against the maximum and relative seed dry weight against the value at maturity as soybean, in addition to pod thickness, were correlated with the timing of when soluble sugar content in seed per fresh weight peaked. Two cultivars of edamame were used, 'Niigata-chamame' and 'Yuagarimusume'. Edamame is usually harvested during the mid to late pod filling stage of the soybean. During this stage, pod thickness increase rate gradually decreases and pod thickness against time is fitted by the quadratic function. Thus, the pod thickness increase rate lin-early decreases with time during the period. At the optimal harvest timing, when sugar content in seed per fresh weight peaks, pod thickness increase rate, relative pod thickness, and relative seed dry weight are estimated to be around 0.15-0.20 mm/d, 90 % and 50 %, respectively.