Optimal artificial light intensity for protected tomato cultivation under LEDs

W. Vanlommel, M. Huysmans, L. Bosmans, R. Vanderbruggen, T. Van Delm
In Belgium, already 25% of the total area of protected tomato crops is equipped with artificial lighting. Most of the artificial lighting still exists of high pressure sodium (HPS) lamps, but light-emitting diode (LED) modules find more and more their way into commercial greenhouses. Nowadays, LEDs are often installed on top of an already existing HPS installation. This way, light intensity and yield is increased, but also the associated electricity consumption. Question remains where the optimum lies, considering yield cannot be increased indefinitely and energy consumption must remain sustainable. In order to find the optimal light intensity, a trial was set up at Research Centre Hoogstraten, Belgium, in October 2017. A tomato greenhouse compartment was equipped with LED toplight modules. By installing the modules in a predefined symmetric pattern and turning the plants locally, 20 treatments with different light intensities were obtained in the same greenhouse. The light intensities ranged between 75 and 330 µmol m‑2 s‑1. A comparison in crop parameters, yield and fruit quality was made for every light intensity. Additionally, the efficiency in light use was determined. Results show that crop parameters are not influenced significantly by the different light intensities. However, yield and fruit weight are positively influenced. Moreover, despite the high light intensities applied, there is still a linear relationship between yield and light intensity. The efficiency in light use is inversely proportional to the applied light intensity. Fruit quality after storage was acceptable according to Belgian auction standards, regardless the installed light intensity.
Vanlommel, W., Huysmans, M., Bosmans, L., Vanderbruggen, R. and Van Delm, T. (2020). Optimal artificial light intensity for protected tomato cultivation under LEDs. Acta Hortic. 1296, 575-582
DOI: 10.17660/ActaHortic.2020.1296.74
artificial lighting, light-emitting diodes, hydroponic crop, Solanum lycopersicon, yield

Acta Horticulturae