S06 - Session P7 - The effect of four different LED spectra on the growth and development of a Cucumber greenhouse crop

Authors: Sebastian Olschowski *, Jonas De Win, David Hawley

Lit cucumber greenhouse production is an emerging market worldwide. Growers often add supplemental light, to ensure plants are adequately performing during the dark fall and winter months and preventing any loss of yield. Historically, growers use HPS lamps to fulfill the lighting requirements. With advances in LED technology, growers are migrating to a newer lighting system with opportunities to affect morphology and yield by applying different light spectra. This study compared the effects of four different LED spectra from a broad to a narrow band spectrum. Light qualities were mixtures of red and broad-spectrum white LEDs, resulting in different fractions of red (R), green (G) and blue (B): (1) Red/Blue, (2) Pink, (3) Broad White/Red, and (4) Broad White. One cucumber cultivar 'Hi-Power' was grown in a high wire system at a planting density of 2,5 plants/m² on rock wool from October 2019 to March 2020. All experimental units were exposed to a light intensity of ~310 μmol m -2 s -1 at a photoperiod of 18 hours in a greenhouse environment. Four simultaneous replicates were executed. Morphological and developmental parameters like plant height, yield and fruit development time were measured. The study showed the highest yield as well as fastest fruit development time in the pink spectrum. Next to this the strongest stem length reduction was observed in the broad white spectrum. Consequently, our experiment recommends suitable LED light regimes for lit cucumber greenhouse production in the winter period.