イチジクの熟成と日射量の関係に関する統計的考察  [in Japanese] Statistical Consideration of Relationship between Solar Radiant Quantity and Fig Maturation  [in Japanese]

Japan does not receive enough solar energy to grow figs. By comparing the received solar energy major fig producing areas of the world and Japan, we have derived the supplemental light energy value, which is the minimum additional light energy necessary for optimal fig maturation. By supplementing natural sunlight with this optimum value by electrical lighting, the fig season in Japan can be lengthened, crop volume increased, and fruit quality improved. The optimum period for fig maturation in Nagoya is from June to September, when the minimum temperature remains above 20℃ in Nagoya, Athens, Izmir, and San Diego. During this same period, however, Athens receives direct sunlight for approximately 1,308hours, while Nagoya gets approximately 638 hours, i.e.about 49% of Athens.These four months also provide average estimated solar energy levels of 17.5 MJ・m^<-2>・day^<-1> for Athens, 15.3MJ・m^<-2>・day^<-1> for San Diego, and 8.8MJ・m^<-2>・day^<-1> for Nagoya. A normal cultivation environment from January to March in winter will require additional supplemental light energy 5.1MJ・m^<-2>・day^<-1> which is derived from the difference in the solar energy between 8.8MJ・m^<-2>・day^<-1> for outdoor maturation in Nagoya and 3.7MJ・m^<-2>・day^<-1> for a green house in winter.