Supplementary light and higher fertigation EC in the cultivation of bromelia improve quality and accelerate growth

Abstract: In order to provide Bromelia growers with lacking information about optimal levels of supplementary light and nutrient EC, two consecutive greenhouse experiments were conducted by Wageningen UR Glasshouse Horticulture in Bleiswijk (The Netherlands). In the first experiment a light intensity gradient (17-155 µmol m-2 s-1 PAR ) was installed in the length direction of two 144 m2 greenhouses. In the width direction four mineral nutrition levels were supplied (EC of 0.6, 1.0, 1.5 and 2.0 dS m-1) to three plant species: Guzmania, Vriesea and Neoregelia (a CAM Bromelia). Each greenhouse had a different (supplementary) photoperiod: 12 or 16 hours. It was concluded that the optimum intensity of supplementary light was 43 µmol m-2 s-1 PAR for Vriesea, and 80 µmol•m-2 s-1 PAR for Guzmania and Neoregelia applied during 12 hours. The corresponding optimum EC of the nutrient solution was 1.5. At higher light levels, longer photoperiod, or the same light levels but nutrition with a lower EC, signs of light damage appeared (chlorotic leaves, reduced plant diameter, red spots on leaves). Neoregelia was tolerant to the 16 hour photoperiod. These optima were validated and compared to a non-lighted control by means of a second experiment with 10 cultivars of 4 different genera grown at a EC of 1.5 dS m-1 under three light levels: 43 µmol m-2 s-1 PAR (applied to all Vriesea and Guzmania ‘Hilda’), 80 µmol m-2 s-1 PAR (applied to Aechmea, Tillandsia, Guzmania ‘Rana’ and Guzmania ‘Tempo’) and no supplementary light (as reference for all varieties). Compared to the reference, the use of supplementary light enhanced plant growth and ornamental quality and it shortened the time to commercial development stage for most studied cultivars, with the exception of Vriesea ‘Miranda’ and Vriesea ‘Stream’.