Abstract
We examined the effect of the late sowing on the isoflavone content of autumn maturing soybean seed in southern Kyushu. The mean air-temperatures during the late ripening stage of the late-sown soybean were 0.4−1.7°C lower than those of the soybean sown on the normal date due to the delay of maturing stage. The isoflavone content was increased by the late sowing. The rate of increase in isoflavone content by the late sowing was 16.1−34.9% in ‘Akisengoku’, 5.9−15.3% in ‘Kurodamaru’, 31.1−37.9% in ‘Hyuga’ and 44.4−58.0% in ‘Fukuyutaka’. The contents of potassium and magnesium were not significantly different between normal sown and late-sown soybean. However, the calcium content of late-sown soybean was lower than that of normal sown soybean. On the other hand, late sowing decreased the seed weight per plant by 78% at the maximum. These results suggest that the late sowing could be an effective cultivation technique for producing soybean with a high isoflavone content on condition that the decrease in seed yield is mitigated.
