The spectrum of grow light influences both photosynthesis and the way a crop grows and develops. With the transition from HPS to LED lighting, growers have more control over individual light colours, making the choice of spectrum an increasingly important part of the lighting strategy.
Spectrum:
Light colours
The importance of light spectrum
Artificial lighting is about more than simply providing enough light. The distribution and uniformity of light, the heat produced by the lighting system and the relationship between light and temperature all influence how efficiently a crop can use the available light.
The e-book How Artificial Lighting Can Optimize Efficiency explores these different elements of a lighting strategy. The first chapters look at the types of heat produced by lighting, including the differences between HPS and LED, and the importance of matching temperature to the available light by measuring PAR (Photosynthetically Active Radiation).
This article focuses on another important element: the spectrum of PAR light. Different light colours contribute to photosynthesis, but they can also influence the growth and development of the crop.
Why choosing the right light spectrum matters
When HPS lamps were the standard for grow lighting, growers had little choice when it came to spectrum. They learned to grow their crops under a fixed light spectrum, even though the light produced by HPS lamps is very different from sunlight. HPS lighting contains relatively large amounts of green and yellow light, and relatively little far-red and blue light.
The transition to LED has changed this. Growers can now choose the spectrum much more precisely and combine specific light colours. This creates new opportunities, but also makes the lighting strategy more complex.
All light colours within the PAR range contribute to photosynthesis. At the same time, individual colours can have specific effects on crop growth and development. The chosen combination of light colours can therefore influence both how the crop produces assimilates and how it develops.
More control also means more choices
For many crops, suitable combinations of light colours are now known. However, knowledge about light spectrum is still developing, particularly for smaller or less extensively researched crops.
Choosing the right spectrum therefore starts with understanding what you want to achieve. Are you switching from HPS to LED primarily to save energy? Are you looking for a safe and proven spectrum, or do you want to maximize production? What light intensity is appropriate for your crop? Which light colours and proportions are needed? And how important are working conditions and crop visibility inside the greenhouse?
There is no single spectrum that is automatically right for every crop or every growing strategy. The best choice depends on the crop, the light intensity, the cultivation goals and the wider greenhouse conditions.
Keep measuring what the crop receives
As lighting systems become more flexible, measuring the light that actually reaches the crop becomes increasingly important. PAR measurements provide insight into the amount of photosynthetically active light available to the plants and help growers evaluate their lighting strategy in practice.
The possibilities of LED lighting continue to grow, but so does the need to understand how light intensity, spectrum and crop response interact. A good lighting strategy therefore combines existing knowledge with careful measurement and observation of the crop.
Want to learn more about artificial lighting?
Choosing the right spectrum is only one part of an effective lighting strategy. The e-book How Artificial Lighting Can Optimize Efficiency explores a broad range of lighting topics, with in-depth knowledge and practical examples to help growers make better-informed decisions.
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