Continuous light can promote growth of baby greens over diurnal light under a high daily light integral
Date
2024-02-23
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Environmental and Experimental Botany
Abstract
Sole-source lighting with light-emitting diodes (LEDs) incurs high operating expenditure in indoor vertical farms, where crops are typically grown under diurnal light at a fixed photosynthetic photon flux density (PPFD). Under the same daily light integral (DLI), continuous light lowers the needed PPFD, thereby decreasing the initial capital investment on high-output LEDs and operating expenditure by lighting in the nighttime, when electricity rates are lower than in the daytime in some areas. However, little is known about how temporal light patterns influence baby green growth at varying DLIs. We performed an indoor experiment on baby greens of lettuce (Lactuca sativa) ‘Rouxai’, kale (Brassica oleracea var. acephala) ‘Red Russian’, and arugula (Eruca sativa) ‘Astro’ at ≈ 21 ºC air temperature and ≈ 70% relative humidity. At each of two DLIs (8.64 and 17.28 mol∙m–2∙d–1), each crop was grown under warm-white LEDs with three light patterns [100%, 75%, and 50% daytime DLI (first half of a 24-hour cycle), followed by 0%, 25%, and 50% nighttime DLI, respectively]. The 0% nighttime DLI treatments delivered diurnal light with a 12-h photoperiod, whereas the 25% and 50% nighttime DLI treatments delivered alternating light and continuous light, respectively, both with a 24-h photoperiod. Lettuce and kale generally had more pronounced growth responses to the light pattern under the higher DLI, whereas arugula growth was unaffected by the light pattern. Compared to diurnal light, continuous light increased lettuce shoot mass at both DLIs, but increased kale shoot mass only under the higher DLI. Compared to continuous light, alternating light decreased lettuce shoot mass only under the higher DLI, but did not influence most parameters of kale or arugula. Doubling the DLI increased the shoot dry mass of all crops by 44–150% and the shoot fresh mass of arugula by 38–73% across light patterns. The shoot fresh mass of lettuce and kale increased with an increasing DLI under continuous or diurnal light. We conclude that the light pattern and DLI had interactive and crop-specific effects on the growth of baby greens. Under the same DLI, continuous light can increase growth of lettuce and kale, but not arugula, baby greens over diurnal light, especially under a high DLI.
Description
This article was originally published in Environmental and Experimental Botany. The version of record is available at: https://doi.org/10.1016/j.envexpbot.2024.105695. © 2024 The Authors. Published by Elsevier B.V.
Keywords
controlled-environment agriculture, indoor vertical farming, leafy greens, LEDs, photoperiod, photosynthetic photon flux density, zero hunger, responsible consumption and production
Citation
Meng, Qingwu, and Stefanie N. Severin. “Continuous Light Can Promote Growth of Baby Greens over Diurnal Light under a High Daily Light Integral.” Environmental and Experimental Botany 220 (April 2024): 105695. https://doi.org/10.1016/j.envexpbot.2024.105695.