LED light spectrum
PAR light, the light that is used by plants for photosynthesis, consists of different wavelengths, which we see as colours. The different wavelength compositions (colours of the light spectrum) of LED not only have effects on the hormonal balance and development of the plant, but also have significant effect on the energy consumption.
Light spectrum report
PAR light, the light that is used by plants for photosynthesis, consists of different wavelengths, which we see as colours. The different wavelength compositions (colours of the light spectrum) of LED not only have effects on the hormonal balance and development of the plant, but also have significant effect on the energy consumption. Read more about our insights on the light spectrum in this report.
About light spectrum
The role of light spectrum in grass growth is crucial. Photosynthetically Active Radiation (PAR light) is the part of the light spectrum used by plants for photosynthesis. Chlorophyll is the green pigment present in plants where photosynthesis takes place. It has two main absorption spectra in the red and in the blue region. With LED light it is possible to supply only light in these regions, which makes it possible to supply light for photosynthesis more efficiently.
The different colours affect the hormonal balance and development of the grass plant. Red light is efficiently used for photosynthesis and promotes plant development. Red light has longer wavelengths than blue light, which means it requires less energy to produce compared to blue light. Blue light, although less efficiently utilised, plays a role in regulating growth and root development. Green light is poorly absorbed. To optimise grass growth and energy efficiency, it is important to design and use a light spectrum that meets the grass’s needs effectively. The quality of a grass plant depends on its roots and shoot, which are influenced by the light source and spectrum. In our study, we investigated three light spectra on the growth of Perennial Ryegrass roots and shoot.
The different wavelength compositions (colours of the light spectrum) of LED not only have effects on the hormonal balance and development of the plant, but also have significant effect on the energy consumption. This means that for every colour, a different amount of energy input is needed to produce it. One of the reasons LED technology can be very sustainable, is the fact that it is possible to compose the light spectrum. In order to be the most energy efficient with LED technology, it’s very important to compose an LED colour spectrum that has the highest quality of growth at the lowest energy consumption.
The effect on growth
In our study, we investigated three light spectra on the growth of Perennial Ryegrass roots and shoot. The red light spectrum is the SGL spectrum (95% red, 5% blue), the white light spectrum resembles the sun’s spectrum (60% red, 20% blue, 20% green), while the blue light spectrum consists of a higher percentage of blue light for comparison (60% red, 40% blue).
Results show that the red and white spectra have the most positive impact, promoting higher dry shoot and root weight. The red spectrum is as effective as the white spectrum, while requiring around 20% less energy. By using the red spectrum, we ensure optimal growth conditions and maximise energy savings, leading to the highest quality grass in a sustainable manner.
Since the agronomical benefits of the red spectrum and the white spectrum are similar, we then looked at energy consumption. As previously mentioned, every colour of the light spectrum requires a different amount of energy to be produced.
The effect on energy efficiency
There are two ways of looking at the energy consumption to compare light spectrum efficiency: either take an equal light output as a starting point and or an equal energy consumption as starting point. In the tables below, you can very clearly see that, in order to produce a light output of 1000 μmol/s/m2, you need a significantly less amount of energy to produce the red spectrum than the green and the blue spectrum (respectively 27% and 21%). Or, if you look at it from an equal energy input point of view, you have a significantly higher light output with the red spectrum than with the green and the blue.
| Colour recipe | Light output | Energy input |
| 95% red | 5% blue | 1000 μmol/s/m2 | 43.7 W |
| 60% red | 40% blue | 1000 μmol/s/m2 | 52.7 W |
| 60% red | 20% blue | 20% green | 1000 μmol/s/m2 | 55.5 W |
| Colour recipe | Energy input | Light output |
| 95% red | 5% blue | 52.7 W | 1194 μmol/s/m2 |
| 60% red | 40% blue | 52.7 W | 1000 μmol/s/m2 |
| 60% red | 20% blue | 20% green | 52.7 W | 950 μmol/s/m2 |
