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A full spectrum of light. 41

Nov 9, 2023 | GILBA BLOG

A rainbow includes all the colours of the light spectrum including blue light
Contents hide
1 A Full Spectrum of Light.
1.1 A full Spectrum of Light.
1.2 Pigments.
2 What is a Full Spectrum Turf Grow Light?
3 Blue light.
4 Red light.
5 Questions
5.1 If I have an infrared heater won’t it throw the light spectrum out?
5.2 Can red light help fight disease?
5.3 Does turfgrass mainly use red light?
5.4 References
5.4.1 Jerry Spencer

A Full Spectrum of Light.

LED turf grow lights for Stadium turf should provide a full spectrum of light for plants so that they supply exactly what the turf grass needs. However, in reality this isn’t always the case.
 
 
As turf agronomists and sports turf consultants we will explain how the composition of the light spectrum effects turf growth and other questions like:
  • Why are some lights pink/purple and some not?
  • How do IR heaters affect the light spectrum?
 
 
 
In order to understand how stadium turf grow lights effect turf grass growth you need to understand what a full spectrum of light means.
 
 
 
When sunlight falls onto your grass it is made up of a rainbow of colours. The three main ones are red, blue, and green. However, this visible light is only part of the light spectrum.
 
 
 

A full Spectrum of Light.

  • The full spectrum of light comprises visible, near infra red (NIR) and Ultra Violet (UV) light.
  • Visible light, has a wavelength of 400 to 700 nm and accounts for 43% of the energy in the global solar irradiance spectrum (300 to 2500 nm).
  • NIR accounts for 52% and has a wavelength of 700 to 2500 nm.
  • UV Light comprises 5% of this spectrum, and has a wavelength of 300 to 400 nm.1Levinson, R., Berdahl, P., & Akbari, H. (2005b). Solar spectral optical properties of pigments– part II: survey of common colorants. Solar Energy Materials and Solar Cells, 89(4), 351- 389.
  • Blue light is in the range of 400-500 nm.
  • Green light is between 500-600 nm.
  • Red light is between 500-600 nm.

 

Plants, including turf grass, use light in the 400 to 700 nm range for photosynthesis, and this is termed photosynthetically active radiation (PAR) light.
 
 
The amount of PAR light turf grass absorbs depends on several factors. These include:
  • The time of year.
  • The amount of cloud cover and
  • The angle of the sun.2Dudeck, A.E. & Peacock, C.H. 1992 Shade and turfgrass culture, p. 269–284 In: D.V. Waddington, R.N. Carrow, and R.C. Shearman (eds.) Turfgrass. ASA Monogr. 32. ASA, CSSA, and SSSA, Madison, WI

 

 
You use photosynthetic photon flux density (PPFD) to measure the amount of light. PPFD measures the photons of PAR light over a base area per second (unit: μmol m−2 s−1).
 
 
You call 24 hours of PPFD measurements the daily light integral (DLI), and its units are mol m−2 d−1.
 
 
Turf plants absorb red light the best, but they also use blue light.3Pridmore, RW, Complementary Colours Theory of Colour Vision: Physiology, Colour mixture, Colour Constancy and Colour Perception. (2011) pp 394-412
 
 

Pigments.

Excess UV light causes significant damage to turf grass in only a short period of time.4Ervin, E. H., Zhang, X., & Fike, J. H. (2004) Ultraviolet-B radiation damage on Kentucky bluegrass. I. Antioxidant and colorant effects. HortScience, 39(6), 1465-1470.

To reduce this damage you can simply a apply synthetic green pigment to turf. This increases the visual quality and also the photochemical efficiency of the turf.

LED grow lights for growing turf should provide the full light spectrum that turf uses

What is a Full Spectrum Turf Grow Light?

A full spectrum turf grow light provides the pefect mix of light that turf needs to fully photosynthesise and recover from wear in shade areas. If you use full spectrum grow lights you are able to grow turf grass from seedlings to full maturity.

 

Blue light.

A full spectrum grow light must contain blue light. If it doesn’t then it doesn’t meet the exact needs of turf grass. Blue light affects chlorophyll production, and turf plants that get plenty of blue light have strong, healthy stems and leaves. Wavelengths between 430 and 450 nm (blue light) promote vegetative growth.
 
Turf in shade or at night does not get enough blue light. So if you’re using stadium light rigs and your light spectrum has no blue in it. Sorry but you’re not getting your bang for your (or your bosses) buck!
 
 

Red light.

 
In the turf grass environment this helps with grass turf seed germination and top growth. In an environment with no shade issues, turf gets plenty of red and blue light.
 
However, In a shade situation (like in a stadium or under trees) turf tends to stretch out and etoliate. Consequently, turf loses the colour in its leaves.
 
Narrow band spectrum LED grow lights have a purple or pink colour and as their name suggests emit a narrow band of light. They are not full spectrum lights and you are not supposed to use them as such.
In horticulture the recommendation is to use pink/purple lights where the plants already receive full sunlight and there are no shade limitations. This is because you are OPTIMISING your growth by adding to the full spectrum of light that plants already receive.
 
 
 
 
So where turf already receives sunlight you should use a high percentage of red to blue light. This is the basis for many stadium light rigs currently sold. High levels of red light in contrast to blue.
 
However, in a shade environment or at night (which is why people use turf grow lights in the first place) this same spectrum limits turf growth.
 
 
 
 
Instead, the idea LED grow light turf should have a custom light spectrum that allows you to produce a full spectrum of light.
 
 
A much broader spectrum is prefered as this allows you to promote plant growth at all stages of the turf grass.
 
 
The bottom line is that you shouldn’t avoid blue light as it is a very important part of the light spectrum. Even more so in shade!

 

Full spectrum LED grow lights

Questions

If I have an infrared heater won’t it throw the light spectrum out?

This is an interesting question. In order to answer it you have to realise that infrared light is further to the right of the visible light spectrum that turfgrass generally uses but that Infrared waves can also affect how plants grow.

An “infrared heater” converts electricity into light and heat as well as emits infrared light.

Turfgrass cannot make use of infrared light for photosynthesis because they lack a pigment which can utilise light with that wavelength.

Plants grown in light that is too red may seem spindly and long-stemmed. Too much infrared light, especially in the far red end of the spectrum, may actually damage plants.

infra red light on the light spectrum

Can red light help fight disease?

There is evidence suggesting that exposing plants to red light increases levels of salicylic acid (SA) and induces SA signalling which is vital for plants to survive fungal infections. That’s all well and good but doesn’t mean you should bombard your turfgrass with red light unless you want it to etiolate. In response to too much red light, it will just make your turf stretch and bleach.

As we keep mentioning a wide LED light spectrum is best which includes red and blue (plus others). If you’re concerned about increasing salicylic acid levels you can make exogenous applications using Vertmax Duo turf pigment which already contains this within its proprietary formulation. That way you increase SA levels get an instant green colouring and avoid your turf becoming like straw!

Does turfgrass mainly use red light?

Contrary to what some say turfgrass uses both red and blue light. Turfgrass gets the hots mainly for blue and red wavelengths. LED grow lighting that only has those colours will not seem very bright but it will be quite effective for grass growth.

References

  • 1
    Levinson, R., Berdahl, P., & Akbari, H. (2005b). Solar spectral optical properties of pigments– part II: survey of common colorants. Solar Energy Materials and Solar Cells, 89(4), 351- 389.
  • 2
    Dudeck, A.E. & Peacock, C.H. 1992 Shade and turfgrass culture, p. 269–284 In: D.V. Waddington, R.N. Carrow, and R.C. Shearman (eds.) Turfgrass. ASA Monogr. 32. ASA, CSSA, and SSSA, Madison, WI
  • 3
    Pridmore, RW, Complementary Colours Theory of Colour Vision: Physiology, Colour mixture, Colour Constancy and Colour Perception. (2011) pp 394-412
  • 4
    Ervin, E. H., Zhang, X., & Fike, J. H. (2004) Ultraviolet-B radiation damage on Kentucky bluegrass. I. Antioxidant and colorant effects. HortScience, 39(6), 1465-1470.
Jerry Spencer senior turf agronomist and soil scientist
Jerry Spencer
Senior Turf Agronomist at  | 0499975819 | [email protected] | Website |  + posts

Graduated from Newcastle University with an Hons Degree in Soil Science in 1988, Jerry then worked for the Sports Turf Research Institute (STRI) as a turf agronomist before emigrating to Australia in 1993.

He followed this by gaining a Grad Dip in Business Management from UTS. He has worked in a number of management roles for companies as diverse as Samsung Australia, Arthur Yates and Paton Fertilizers.

He has always had a strong affinity with the Australian sports turf industry and as a result he established Gilba Solutions as an independent sports turf consultancy in 1993. Jerry has written over 100 articles and two books on a wide range of topics such as Turf Pesticides and Nutrition which have been published in Australia and overseas.

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