Possibility of Increasing Lower Internode Length by Raising Seedlings to Improve Mechanical Harvesting Adaptability in Black Soybean 'Tambaguro' for Edamame (Green Soybean)

Abstract

To improve the mechanical harvestability of black soybean 'Tambaguro' edamame (green soybean) cultivars bred in Kyoto Prefecture, we investigated the effects of different cell plug trays for seeding and seedling raising duration on the lower internode length, which affects the height of lower epiphytic pods, during the two-year period from 2021 to 2022. In 2021, we analyzed the effect of three factors in a total of 16 experimental areas. We used the four varieties: 'Natsudoritambaguro 2', 'Murasakizukin 2', 'Murasakizukin 3' and 'Shintambaguro', 128-cell and 200-cell plug trays, seedlings raising duration of 10 and 14 days and the analysis of variance (ANOVA). At the time of transplanting, the effects of all factors and interactions were significant for seedling main stem length, whereas only the effect of varieties was significant for hypocotyl length. At harvest, the effects of variety and seedling raising duration and the interaction between variety and seedling raising duration were significant for both first and second internode lengths. In 2022, two varieties: 'Natsudoritambaguro 2' and 'Murasakizukin 2', four growth methods for raising seedlings using different combinations of cell plug trays and seedling raising durations were investigated. The two factors and eight experimental areas analyzed by the ANOVA. As in 2021, the first and second internode lengths increased significantly at harvest with the increase in seedling raising duration. On the other hand, the effects of cell plug tray difference on the main stem were limited to the seedling growth.