2016 年 60 巻 3 号 p. 185-190
The effect of fertilization on lesser yam (Dioscorea esculenta L.) growth is not clearly understood. Increased lesser yam production in Okinawa prefecture, Japan, is desired due to increasing demand for use in commercial health supplements. However, fertilization guidelines for production are not yet available in Japan. This study aimed to reveal the effects of nitrogen application on growth of lesser yam in Okinawa from April 2014 to January 2015. Growth with urea application (N treatment) and without urea (control) were compared. N treatment had a positive effect on growth and tuber yield in soil with poor organic matter. Yellowish leaves were observed in control plants from 120 days after planting (DAP), but plants grew until 240 DAP. It was possible to grow lesser yams under poor fertile soil conditions. The δ15N values of the N treated plants suggested that nitrogen was absorbed from the urea; however, the source of nitrogen in the control plants was not identified. The quantity of nitrogen required for a stable yield of lesser yam is thought to be less than that required for water yam (D. alata).
