Energy Use Efficiency as a Practical Criterion for Comparing LED Lighting Systems in Runner Propagation of Strawberry cv. ‘Berry Pop Haruhi’

Light-emitting diode (LED) systems for strawberry propagation are usually compared on plant responses, rarely on electricity per propagule. Five LED lighting systems differing in spectral composition (red:blue photon ratios 1.56–4.07; far-red fractions 0.004–0.262) were compared at a common target canopy photosynthetic photon flux density (PPFD) of 250 µmol m−2 s−1 in container-grown strawberry cv. ‘Berry Pop Haruhi’ over 28 days. Each spectrum was delivered by a single unreplicated fixture array, so the study is an exploratory observational comparison of lighting systems, not a test of spectral effects. The effective quantum yield of photosystem II, petiole length and lamina size differed among the lighting environments, whereas maximum quantum yield, crown diameter, stolon number (5.00–5.43 per plant) and daughter plant number (3.07–3.71 per plant) showed no significant differences; the design could resolve differences of about one fifth to one quarter of the mean. Lamina size corresponded most closely with the far-red fraction, which was confounded with a higher total photon flux. With no detectable difference in propagule output, energy use efficiency, calculated from rated fixture power, differed about 1.5-fold, from 0.78 daughter plants kWh−1 (broad-spectrum white) to 0.51 (red:blue). These differences reflect the fixture power each system required to reach the target PPFD, not spectrum alone, and apply only to the conditions tested.