Comparison of LEDs, Fluorescent Lamps and Incandescent Bulbs for Long-day Treatment of Forcing Strawberries as Affected by Respective Color Temperature

Long day (LD) treatment is frequently applied for horticultural crops, including strawberry, and sufficient effect similar to 4 to 6hours of day time elongation in the evening can be achieved by 1 to 3hours of night break in the mid night. Incandescent lamps (IC) have long been an important light source, but the general incandescent lamps are out of production and have been replaced with LED or florescent lamps (FL). Thus, we compared light sources and their color temperature (2,800K, warm white similar to IC; 6,500K, daylight) in different lighting programs. The effectiveness of 3 and 4cycles of alternate intermittent lighting, 30min on/30min off, were equal to and larger than 2hours of night break, respectively. Measured intensity of illumination (lux) at the canopy surface by 2,800K LED (6.9W) and FL (12W) was 1.50 and 0.95times as large as IC (54W), but leaf growth under LED and FL was similar to and less vigorous than IC, respectively. On the other hand, intensity values of illumination by 6,500K LED (6.9W) and FL (12W) were both 1.20times as large as 2,800K ones, but 6,500K light sources were much less effective compared to 2,800K ones. Daylight type LED and FL which have higher luminance efficiency but emit less red light compared to warm white ones, are not suitable as alternative light sources for IC.

原著論文 (Original paper)