Growth of Water Yam (Dioscorea alata L.) under Alkaline Soil Conditions

抄録

Water yam (Dioscorea alata L.) are adaptable to cultivation under different soil conditions. This study aimed to reveal the effects on the growth of water yam under natural alkaline soil conditions (called Shimajiri Mahaji locally) at the Miyako Islands, Okinawa Prefecture in 2011 and under three fertilizer levels and varied pH in the greenhouse at Setagaya, Tokyo, Japan in 2012. The Shimajiri Mahaji soil for this experiment was of poor fertility with a pH of 7.9. The application of a larger quantity of fertilizer did not affect plant growth. The lack of effect of N: P: K fertilizer on the yield of ‘Okinawa white’ yam might have been due to the disturbance of mineral absorption by the alkaline soil conditions. The effect of alkaline soil conditions (pH 8.0) on the growth of five water yam cultivars including ‘Okinawa white’ was investigated at Tokyo, Japan. Plant growth varied among cultivars under alkaline soil conditions, in which some cultivars grew well. No Fe or Mn deficiency symptoms were observed on any tested cultivars under alkaline soil condition. The dry weights of tops and roots of ‘Okinawa white’ were smaller compared to control in alkaline soil, but the dry weight of tubers was not significantly different. Water yam could adapt to alkaline soil conditions, depending on the cultivar. Thus, different fertilization guidelines for the cultivation of adaptable cultivars of water yam on alkaline soils such as Shimajiri Mahaji should be developed.