J. Werner, Y. Okada, M. Karlsson
Many regions are dependent on supplemental lighting for producing greenhouse crops year round. Light emitting diodes (LEDs) show promise to complement and replace current equipment for supplemental lighting. LEDs are more energy efficient, offer opportunities to customize the light quality, and have an extended high output operational time range. LED panels developed to support crop growth often provide light in the blue and red portion of the spectrum. Most physiological processes in addition to photosynthesis are however, affected by the overall quality of the incoming light. Research is needed on proper LED wavelength composition, configurations and photosynthetic photon flux (PPF) to most effectively support growth and proper crop development. LED panels (150, 300, 600 W) with red LEDs (peak emission at 665 nm) supplemented with 10% blue LEDs (peak emission at 456 nm) were compared to high pressure sodium (HPS) and metal halide (MH) lamps in a controlled environment production area. Black-eyed susan (Rudbeckia hirta ‘Toto’) was grown in 10 cm containers 100 cm below the sources of light. PPF (400 to 700 nm) varied from 65±10 mol m-2 s-1 under the 150 W LED panel to 130±15 mol m-2 s-1 under the 300 W panel, and 300±20 mol m-2 s-1 under the 600 W LED array. In comparison, PPF was 200±20 mol m-2 s-1 in the growing environments of HPS and MH. After 21 days, at least 50% of the plants had developed visible flower buds (2 mm) under HPS, MH, and the 300 W LEDs. All plants in the 600 W LED environment had visible buds at 21 days. Early development and growth of black-eyed susan in respect to height and leaf number were comparable to HPS when the LEDs provided 300 mol m-2 s-1.
Werner, J., Okada, Y. and Karlsson, M. (2011). USING LIGHT EMITTING DIODES IN HIGH LATITUDE GREENHOUSE PRODUCTION. Acta Hortic. 907, 287-290
DOI: 10.17660/ActaHortic.2011.907.46
black-eyed susan, controlled environment agriculture, high pressure sodium lamps, light quality, metal halide lamps, Rudbeckia hirta

Acta Horticulturae