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Wesley C. Randall and Roberto G. Lopez

seedlings grown under SSL to those grown under SL in a greenhouse providing the same DLI. The objectives of this study were to 1) quantify the effects of SL from HPS lamps and LED arrays compared with a SSL multilayer production system from LED arrays

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Joshua R. Gerovac, Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

Multilayer vertical production systems using sole-source (SS) lighting can be used for the production of microgreens; however, traditional SS lighting methods can consume large amounts of electrical energy. Light-emitting diodes (LEDs) offer many advantages over conventional light sources, including high photoelectric conversion efficiencies, narrowband spectral light quality (LQ), low thermal output, and adjustable light intensities (LIs). The objective of this study was to quantify the effects of SS LEDs of different light qualities and intensities on growth, morphology, and nutrient content of Brassica microgreens. Purple kohlrabi (Brassica oleracea L. var. gongylodes L.), mizuna (Brassica rapa L. var. japonica), and mustard [Brassica juncea (L.) Czern. ‘Garnet Giant’] were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m−2·d−1 was achieved from commercially available SS LED arrays with light ratios (%) of red:green:blue 74:18:8 (R74:G18:B8), red:blue 87:13 (R87:B13), or red:far-red:blue 84:7:9 (R84:FR7:B9) with a total photon flux (TPF) from 400 to 800 nm of 105, 210, or 315 µmol·m−2·s−1 for 16 hours. Regardless of LQ, as the LI increased from 105 to 315 µmol·m−2·s−1, hypocotyl length (HL) decreased and percent dry weight (DW) increased for kohlrabi, mizuna, and mustard microgreens. With increasing LI, leaf area (LA) of kohlrabi generally decreased and relative chlorophyll content (RCC) increased. In addition, nutrient content increased under low LIs regardless of LQ. The results from this study can help growers to select LIs and LQs from commercially available SS LEDs to achieve preferred growth characteristics of Brassica microgreens.

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David Llewellyn, Youbin Zheng, and Mike Dixon

and will serve to help growers and industry support representatives make informed decisions about multilayer production systems. Units Literature cited Al Ani, K.E. Anabtawi, M. 2012 UV-irradiation effect on the photodegradation of plasticized

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Joshua K. Craver, Joshua R. Gerovac, Roberto G. Lopez, and Dean A. Kopsell

more efficient lighting methods has benefited the introduction of multilayer production on shelving units using SS lighting ( Gerovac et al., 2016 ; Goto, 2012 ). With the introduction of these technologies, the manipulation of plant products for