Development of a Cropping Type Based on the Flowering Habit of the Early Black-seeded Soybean “Tambaguro” for Edamame (Green Soybean) “Kyo Natsuzukin”, in Kyoto Prefecture

Two edamame (green soybean) cultivars, “Natsudoritambaguro 1” and “Natsudoritamabaguro 2”, were bred in 2009 as new early black soybean in Kyoto prefecture and are called, "Kyo Natsuzukin" (commercial name). In order to develop cropping types for stable production of these cultivars, the flowering characteristics under different photoperiods, and the suitable sowing time outdoors and in plastic greenhouses were examined. The critical day length was detected in “Murasakizukin 2”, and “Shintambaguro”, but “Natsudoritambaguro 1” and “Natsudoritambaguro 2” flowerd independent of day length. By changing the sowing time from April 15 to May 24 in the transplanting culture of “Kyo Natsuzukin” under outdoor conditions, the harvesting time also changed from July 20 to Aug. 23. The sowing time suitable to obtain a target yield (400 g m–2 fresh weight pods with over 10 mm thickness), was from early to late May, with harvesting from early to late August. Although sowing in April allowed harvesting in middle to late in July, it reduced the pod number and yield compared with those in May and April sowing. To combine the earlier harvesting and stable yield in the unheated plastic greenhouse, later than late-May sowing and later than early-April transplanting, and harvesting in middle to late June may be necessary because vegetative growth was poor and pod number and yield were small in the culture sown on March 1. A close relation was found between the amount of vegetative growth and the pod yield in “Kyo Natsuzukin” cultivars used in this study.