The Effects of High Groundwater Level on the Growth and Yield of Supernodulating Soybean Cultivar "Sakukei 4" with Special Reference to Flowering and Seed-Setting Habit

Abstract

Supernodulating soybean cultivar "Sakukei 4" has a high nitrogen fixing activity. The yield of soybean is reduced under high groundwater-level conditions, but the reduction might be mitigated by using such cultivars. In this study, we investigated the yield of Sakukei 4 treated with a high groundwater level at different times, especially at the time of flowering and seed set. The cultivars Enrei and Sakukei 4 differed in the growth period during which a high ground water level treatment affected the number of flowers and seed weight. In both cultivars, the number of flowers and seed weight were decreased by the high ground water level treatment applied during the floral differentiation stage. The high ground water level treatment applied during the flowering time did not promote the falling of flowers and pods in Enrei, but promoted it in Sakukei 4. The main reason for the decrease in yield of Sakukei 4 was the falling of flowers and pods in high-order racemes and the decrease in the pod number. In this study, the use of supernodulating soybean cultivar Sakukei 4 did not mitigate the yield reduction under the high ground water level conditions at the time of flowering.