No abstract

Supernodulating soybean cultivar "Sakukei 4" has a high nitrogen fi xing 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 fl owering 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 fl owers and seed weight. In both cultivars, the number of fl owers and seed weight were decreased by the high ground water level treatment applied during the fl oral differentiation stage. The high ground water level treatment applied during the fl owering time did not promote the falling of fl owers 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 fl owers 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 fl owering. Key words Flowering and seed-setting habit, High groundwater level, Number of pod, Sakukei 4, Soybean (Glycine max (L.) Merr.).