Opinions on the best spectrum for growing
Posted: Mon Aug 13, 2018 9:15 am
Hello everyone!
The LED grow community worldwide have widely adopted warm white as an excellent flowering spectrum, with great results to show for it. We're seeing high yields with high quality, even where the light output has relatively low to no UV, and also relatively low 660nm frequency.
What we're also seeing is a push toward standardisation to some degree of the nomenclature around LED lights, in an attempt to do away with the bullshit we've all been force fed for the last seven years or so.
Right now it seems there is a big focus on the efficiency of grow lights, with primary players now quoting efficiency values in uMol/J... and rightly so, as it's easily calculable and quantifiable.
Something that isn't so quantifiable however, is the direct effect on plant growth that the spectrum has... it paints an incomplete picture.
Say for example you take two different hypothetical grow lights rated at the same wattage... the first one producing 2.0 uMol/J, the other 2.4 uMol/J. Upon initial inspection, one would assume the 2.4 uMol/J should grow more and better plants with a higher yield, right?
But much like judging the value of a car on mileage alone, this isn't really everything is it? After all, discrete 660nm red LEDs return very high uMol/J values in isolation.
We have some science such as the McCree study which has created a fairly universal curve, reporting on the photosynthetic efficiency of a wide variety of plants. And using this we can therefore convert PPFD from a known spectrum, into YPFD, a McCree weighted version of PPFD which is one supposed way to know the actual efficiency of a given light.
But how can we really quantify the true efficiency gain of spectrum quality, alongside the known electrical efficiency?
Going back to my hypothetical lights... what if the 2.0 uMol/J light had a much better spectrum for not only photosynthesis, but accessory pigment stimulation which has been shown to further improve and accelerate biological processes within the plant, leading to healthier plants with better terpene profiles and so forth?
What if the resultant synergy between spectral quality and efficiency actually led to the 2.0 uMol/J light being capable of producing higher yields and better quality than the 2.4 uMol/J light?
Personally I think taking warm white and adding discrete 660nm is somewhat rudimentary and almost lazy... and I haven't seen anybody produce any quantifiable evidence that there's a huge benefit in doing so. Only very recently for example, has it been determined that plants make much better use of green spectrum light when PPFD is high, and that it has better canopy penetration power than the reds and the blues.
Plants have been evolving under the sun for over 400 million years. Natural sunlight varies, and doesn't have this big red spike in the spectrum. I do wonder whether everybody is barking up the wrong tree thinking 660nm is all that. I have been configuring grow lights with a higher blue to red ratio since 2011; stretch sucks balls, more blue reduces it.
I'd love to hear your opinions on the best way to go forward:
Do you think we should be configuring grow lights to match the McCree curve? If so, then the McCree curve shows a lot more variety of blues in the mix.
Or should we be trying to mimic the sun more accurately, given that plants evolved under it?
Do you think efficiency in and of itself is sufficient to make a choice about grow lights?
Do you think we need a new unit or a new way of expressing the true efficiency of a grow light, not just the uMol/J by itself?
Knowing what I know and having studied this at university level, being able to control the biological processes that result from the light spectra seems to be massively overlooked by conventional spectrum grow lights... with almost too much of a focus on raw "horsepower" if you will. I believe having some control over plant morphology, phytochrome switching and all that good stuff should be the standard now... and we should really be considering spectral quality on top of efficiency.
Just remember, diodes are very cheap, and you can just use a whole bunch more at the same current if you want to up your efficiency... but designing an optimal, adjustable spectrum board... that's where it's at. I'm developing something like this at the moment.
The LED grow community worldwide have widely adopted warm white as an excellent flowering spectrum, with great results to show for it. We're seeing high yields with high quality, even where the light output has relatively low to no UV, and also relatively low 660nm frequency.
What we're also seeing is a push toward standardisation to some degree of the nomenclature around LED lights, in an attempt to do away with the bullshit we've all been force fed for the last seven years or so.
Right now it seems there is a big focus on the efficiency of grow lights, with primary players now quoting efficiency values in uMol/J... and rightly so, as it's easily calculable and quantifiable.
Something that isn't so quantifiable however, is the direct effect on plant growth that the spectrum has... it paints an incomplete picture.
Say for example you take two different hypothetical grow lights rated at the same wattage... the first one producing 2.0 uMol/J, the other 2.4 uMol/J. Upon initial inspection, one would assume the 2.4 uMol/J should grow more and better plants with a higher yield, right?
But much like judging the value of a car on mileage alone, this isn't really everything is it? After all, discrete 660nm red LEDs return very high uMol/J values in isolation.
We have some science such as the McCree study which has created a fairly universal curve, reporting on the photosynthetic efficiency of a wide variety of plants. And using this we can therefore convert PPFD from a known spectrum, into YPFD, a McCree weighted version of PPFD which is one supposed way to know the actual efficiency of a given light.
But how can we really quantify the true efficiency gain of spectrum quality, alongside the known electrical efficiency?
Going back to my hypothetical lights... what if the 2.0 uMol/J light had a much better spectrum for not only photosynthesis, but accessory pigment stimulation which has been shown to further improve and accelerate biological processes within the plant, leading to healthier plants with better terpene profiles and so forth?
What if the resultant synergy between spectral quality and efficiency actually led to the 2.0 uMol/J light being capable of producing higher yields and better quality than the 2.4 uMol/J light?
Personally I think taking warm white and adding discrete 660nm is somewhat rudimentary and almost lazy... and I haven't seen anybody produce any quantifiable evidence that there's a huge benefit in doing so. Only very recently for example, has it been determined that plants make much better use of green spectrum light when PPFD is high, and that it has better canopy penetration power than the reds and the blues.
Plants have been evolving under the sun for over 400 million years. Natural sunlight varies, and doesn't have this big red spike in the spectrum. I do wonder whether everybody is barking up the wrong tree thinking 660nm is all that. I have been configuring grow lights with a higher blue to red ratio since 2011; stretch sucks balls, more blue reduces it.
I'd love to hear your opinions on the best way to go forward:
Do you think we should be configuring grow lights to match the McCree curve? If so, then the McCree curve shows a lot more variety of blues in the mix.
Or should we be trying to mimic the sun more accurately, given that plants evolved under it?
Do you think efficiency in and of itself is sufficient to make a choice about grow lights?
Do you think we need a new unit or a new way of expressing the true efficiency of a grow light, not just the uMol/J by itself?
Knowing what I know and having studied this at university level, being able to control the biological processes that result from the light spectra seems to be massively overlooked by conventional spectrum grow lights... with almost too much of a focus on raw "horsepower" if you will. I believe having some control over plant morphology, phytochrome switching and all that good stuff should be the standard now... and we should really be considering spectral quality on top of efficiency.
Just remember, diodes are very cheap, and you can just use a whole bunch more at the same current if you want to up your efficiency... but designing an optimal, adjustable spectrum board... that's where it's at. I'm developing something like this at the moment.