2018 ASHS Annual Conference

Light-emitting diodes (LEDs) have been a viable method for providing supplemental lighting (SL) in a range of greenhouse crops for many years, however their general adoption still has not become the standard practice in many greenhouse production systems. As the operating efficiencies of LEDs continue to increase, installing fixtures at a density to provide upwards of 300 µmol·m^-2·s^-1 is no longer a rare occurrence in high-light crops. However, due to the high capital cost of LEDs for SL, there must be an additional benefit of SL beyond increased production. In partnership with two commercial greenhouse operations, we have conducted a multi-year, multi-crop investigation into the optimal SL intensities for production of greenhouse cucumbers and strawberries, followed by quantifying the effect of SL spectrum on yield and fruit quality. For strawberry and cucumbers, adding SL reduced time to first harvest and promoted early yield. Through economic modeling we determined SL intensity of 85 µmol·m^-2·s^-1 was optimal for strawberry production for the grower’s specific location and production system, but further analysis is required to determine optimal SL spectrum for fruit quality beyond yield. Additional challenges involved with conducting lighting experiments in a commercial environment such as light contamination effects, environmental changes, and grower expectations will also be presented. These findings and experiences should be integrated into future lighting experiments at commercial facilities.