Effect of daytime intra-canopy LED illumination on the fruit yield and quality of bell pepper grown in high tunnels

Intra-canopy illumination using light-emitting diodes (LEDs) is a technique used to supplement the inside of the canopy of intensively grown crops with light. Bell pepper grown in double-row beds using ‘Spanish’ trellis systems during the winter suffers from considerable shading of the inner canopy. Moreover, under passive growth conditions, limited light availability and low temperature over the winter may attenuate photosynthetic efficiency and result in non-optimal fruit set and therefore less yield. In our studies, we found that intra-canopy illumination operated during daytime or edge-of-daytime in passive growth tunnels increased the spring fruit yield of the bell pepper cultivar ‘Cannon’. In this paper, we report on a study with daytime intra-canopy illumination carried out with the cultivar ‘Gilad’ in the Jordan Valley. Along the growth season, we studied the effect of the added illumination on physiological parameters, fruit yield and quality. Our results show that the LED illumination significantly increased gas exchange activity and photosynthetic assimilation of the inner canopy without causing any light or heat stress. The fruit yield increased by ~20% in spring in the illuminated plots, with the majority of the yield increase (higher fruit number) arising from western-facing plants of the double-row beds. Postharvest quality parameters differed for different harvests along the season, yet no considerable differences were found between fruit from illuminated or non-illuminated plants per harvest. Thus, the supplemental illumination resulted in an increase to the yield without compromising fruit quality.