Optimizing vertical light spectral distribution to improve yield and quality in greenhouse fruit vegetable production

Different spectra of light trigger different plant growth processes.
Therefore, the optimum light spectrum for various plant growth processes, such as leaf and fruit growth, may be different.
Greenhouse fruit vegetables, such as tomatoes, cucumbers and sweet peppers are of tall crops, with most leaf growth occurring in the top and middle canopy and fruit growth occurring in the middle and bottom canopy.
Therefore, optimized vertical light spectral distribution profiles could be developed for improving both vegetative and generative growth, and fruit quality.
The availability of light emitting diodes (LEDs, narrow spectral compositions and low surface temperature for intra-canopy application) has made this possible.
A research project was initiated in 2013 to optimize the vertical spectral distribution of supplemental lighting for greenhouse fruit vegetable production.
Four winter experiments (Oct. to May) were conducted from 2013 to 2017 in a large greenhouse (200 m²). The greenhouse was divided into 4 sections (50 m²/section) so that 2 different overhead (above crop canopy) light spectral compositions can be applied with 2 replications.
Four different intra-canopy light spectral compositions, provided by LEDs, were applied to 4 plots inside each section.
A total of 8 vertical light spectral distribution regimes were tested in these experiments.
Same amount of overhead light and intra-canopy light was applied to all 8 vertical regimes.
The vertical regimes resulted in significant differences in leaf photosynthesis, leaf size, fruit yield and quality in greenhouse tomatoes, mini-cucumbers and sweet peppers.
Proper vertical light spectral distribution regimes were identified for hybrid light systems (overhead high intensity discharge (HID) light and intra-canopy LEDs) and for pure LED light systems (Overhead LEDs and intra-canopy LEDs). This study has clearly demonstrated that optimized vertical light distribution profiles can be developed for improving both plant growth and fruit yield and quality in year-round greenhouse tomato, mini-cucumber and sweet pepper production with supplemental lighting.

XXX International Horticultural Congress IHC2018: III International Symposium on Innovation and New Technologies in Protected Cultivation

X. Hao, R. Cao, J. Zheng, C. Little, S. Kholsa, M. Yelton

vertical light spectral distribution, light quality, LED, lighting, tomato, sweet pepper, Solanum lycopersicum, Capsicum annuum

https://doi.org/10.17660/ActaHortic.2020.1271.20