Cultivation of the black-seeded soybean “Tambaguro” for Edamame (green soybean) “Murasakizukin 2” in Kyoto Prefecture: Effects of sowing time, planting density and topdressing at the molding time

In order to establish a cultivation method to obtain a stable yield of black-seeded soybean ‘Tambaguro’ for Edamame (green soybean) cv. ‘Murasakizukin 2’ in Kyoto prefecture, we investigated the effect of sowing time, planting density, fertilizer type and amount of nitrogen topdressing at the molding time on pod yield of ‘Murasakizukin’. The harvesting time was shifted by changing sowing time, but the shift of harvesting time was shorter than that of sowing time. The optimal sowing time was from mid to late June because by delaying the sowing time, the havesting time was shifted to almost the same time as that in ‘Murasakizukin’, and by advancing sowing time, the yield and the ratio of pods more than 11 mm in thickness to total pod weight was decreased. The total number of pods and total pod weight per m² increased with increasing planting density, but the weight ratio of pods more than 11 mm in thickness to that of total pods was decreased by decreasing the hill distance to 20 cm. Therefore, the planting density suitable for ‘Murasakizukin 2’ was considered to be 30–40 cm in hill distance and 90 cm in row spacing. Top dressing with 40-day sigmoidial-releasing type coated urea (CUS40), controlled release fertilizer, at the molding time, increased the total pod weight and weight of pods more than 11 mm in thickness in a low yield year, such as 2008, but not in a high yield year such as 2009.