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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 Visible Light.
1.2 Pigments.
2 What is a full spectrum 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.

An LED grow light for growing turf provides a full spectrum of light for plants to supply exactly what the turf grass needs. But why are some lights pink/purple and some not? As turf agronomists and sports turf consultants we will try and explain how the composition of the light spectrum effects turf growth.
 
In order to understand the reason you need to understand what the full spectrum of light means. At the end of this are questions and answers section that will clear up some of the confusion out in the marketplace.
 
When sunlight falls onto your grass it is actually made up of a rainbow of colours with the three major ones being red, blue, and green. This visible light is only part of the light spectrum.
 

A full Spectrum of Visible Light.

Visible light (400 to 700 nm) accounts for 43% of the energy in the global solar irradiance spectrum (300 to 2500 nm). The balance arrives as 52% near-infrared (NIR; 700 to 2500 nm) and 5% ultraviolet (UV; 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 in the range of 400-500 nm, between 500-600 nm is green light, and between 500-600 nm is red light. Plants use light in the 400 to 700nm range for photosynthesis. This term for this light is photosynthetically active radiation (PAR) light.
 
The amount of PAR light turfgrass absorbs depends on several factors. These include the time of year, cloud cover and even the angle of the sun2Dudeck, 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. This measures the photons of the PAR band 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 as well as blue3Pridmore, RW, Complementary Colours Theory of Colour Vision: Physiology, Colour mixture, Colour Constancy and Colour Perception. (2011) pp 394-412.
 

Pigments.

Ultra-violet light can cause significant visual and photosynthetic damage to turfgrass species in only a short period of time4Ervin, 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.. As a result of this it has been found that to reduce this you can apply synthetic green pigment to Poa pratensis and get significantly higher visual quality and photochemical efficiency.

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

What is a full spectrum grow light?

A full spectrum grow light provides the optimal light needed for turfgrass to fully photosynthesise and recover from wear in shade areas.  By using full spectrum grow lights you are able to grow turfgrass from seedlings to full maturity.

 

Blue light.

A full spectrum grow light must contain blue light. If it doesn’t then it isn’t providing the complete needs of turfgrass. Blue light directly 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 turf 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 turfgrass environment this helps with sports turf seed germination and top growth. In an open sportsground situation with no issues with shade, 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 for growing have a purple or pink colour and emit a narrow band of light. They are not full spectrum lights and are not supposed to be used as such.
In horticulture the recommendation is to use these pink/purple lights where plants are already receiving full sunlight. This is because you are OPTIMISING your growth by supplementing the full spectrum of light that plants receive.
 
 
 
So where turf is already receiving sunlight ideally you should use a high percentage of red to blue light.
 
 
However, in a shaded environment or at night (which is why people use turf grow lights in the first place) this same spectrum limits optimal turf growth.
 
 
 
 
Instead any LED grow light for growing turf should have a custom light spectrum that allows you to produce a full spectrum of light.  A much broader spectrum is preferable as this is optimized for all stages of turfgrass growth. This means that you shouldn’t avoid the use of 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 Gilba Solutions Pty Ltd | 0499975819 | 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.