Articles
Dynamic continuous LED lighting can reduce light fixture and energy costs and improve energy efficiency in greenhouse tomato production
Article number
1377_39
Pages
325 – 332
Language
English
Abstract
The improvement in plant productivity by supplemental lighting in greenhouse vegetable production is directly related to the total amount of light supplemented during a day (daily light integral (DLI) intensity × photoperiod). It is more economical to achieve the desired DLIs with long photoperiods of low intensity light because it reduces light fixture costs.
Furthermore, long photoperiods of lighting such as continuous lighting (CL, 24h) can reduce energy costs because the heat generated from lighting can partially or fully meet the heating demand during the otherwise dark night period and electricity price is normally lower during the night than daytime in many jurisdictions.
However, lighting >16-17 h causes photo-injury such as leaf chlorosis and limits the yield increase in greenhouse tomatoes.
Smart LED lighting systems which allow the dynamic change of light intensity and spectrum have been developed recently by several LED manufacturers.
In a previous study, we found that dynamic LED CL lighting with monochromatic 50 µmol m‑2 s‑1 blue light during the night can eliminate photo-injury and does not compromise fruit production.
In this study, we expanded the research to a high light intensity and examined more light spectra during the night to move more light from day to night time and to further reduce light fixture and energy costs.
The study was conducted in a 200 m2 greenhouse from Oct. 2020 to Apr. 2021. The greenhouse was divided into 20 plots using curtains impermeable to light to accommodate 5 lighting treatments.
Four CL treatments with 45 or 95 µmol m‑2 s‑1 blue or red light during the night plus one CL with broad spectrum light during the night were applied to the plots.
The CL treatment with broad spectrum light resulted in leaf chlorosis, smaller leaves and lower yield than other 4 CL treatments while there was no difference in leaf chlorosis, plant growth and fruit production among the 4 CL treatments with red or blue light during the night.
Therefore, up to 95 µmol m‑2 s‑1 monochromatic red or blue light can be used during the night to further reduce light fixture and energy costs without compromising plant growth and fruit production.
Furthermore, long photoperiods of lighting such as continuous lighting (CL, 24h) can reduce energy costs because the heat generated from lighting can partially or fully meet the heating demand during the otherwise dark night period and electricity price is normally lower during the night than daytime in many jurisdictions.
However, lighting >16-17 h causes photo-injury such as leaf chlorosis and limits the yield increase in greenhouse tomatoes.
Smart LED lighting systems which allow the dynamic change of light intensity and spectrum have been developed recently by several LED manufacturers.
In a previous study, we found that dynamic LED CL lighting with monochromatic 50 µmol m‑2 s‑1 blue light during the night can eliminate photo-injury and does not compromise fruit production.
In this study, we expanded the research to a high light intensity and examined more light spectra during the night to move more light from day to night time and to further reduce light fixture and energy costs.
The study was conducted in a 200 m2 greenhouse from Oct. 2020 to Apr. 2021. The greenhouse was divided into 20 plots using curtains impermeable to light to accommodate 5 lighting treatments.
Four CL treatments with 45 or 95 µmol m‑2 s‑1 blue or red light during the night plus one CL with broad spectrum light during the night were applied to the plots.
The CL treatment with broad spectrum light resulted in leaf chlorosis, smaller leaves and lower yield than other 4 CL treatments while there was no difference in leaf chlorosis, plant growth and fruit production among the 4 CL treatments with red or blue light during the night.
Therefore, up to 95 µmol m‑2 s‑1 monochromatic red or blue light can be used during the night to further reduce light fixture and energy costs without compromising plant growth and fruit production.
Authors
Xiuming Hao, J. Lanoue, Jingming Zheng, C. Little
Keywords
Solanum lycopersicum, light spectrum, leaf chlorosis, photoperiod, continuous light, yield
Groups involved
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