Effect of Supplemental Light on the Quality of Green Asparagus Spears in Winter ‘Fusekomi’ Forcing Culture

Winter ‘fusekomi’ forcing culture of asparagus is becoming popular in Japan because the method can make production of asparagus possible during cold season. However, there are some problems such as color of the spear is pale, and rutin content is lower compared to spring harvest due to the low light intensity, especially in the production area which has much snow and short sunshine. The objective of this study was to clarify the effect of supplemental lighting on the yield, rutin content, sugar component (fructose, glucose, sucrose), and the color of spears. The experiments were conducted by using different irradiation time and different numbers of fluorescent lamps hanging on the tunnel poles over the cultivation bed on the winter ‘fusekomi’ forcing culture. Compared to the control, rutin content was significantly increased under supplemental lighting plots. No significant difference or negative impact was observed in sugar contents and yield on each plot. Moreover, spear color also appeared to be better under supplemental lighting than that of the control. These results suggested that supplemental lighting was effective to improve the quality of asparagus spears (such as rutin contents, spears color), especially for the production area that has low light intensity or in short day conditions.