Hey Dan, LED Teknik and I have this duscussion all the time: spectrum vs efficiency.
Teknik is a LED guru. I'm a grower (and have been for 30+ years). Much of what I've learned about LEDs is through him, and much of what he's learned about growing is through me, so we bounce ideas off each other all the time. To his credit, Teknik was the one who suggested bumping the far red to much higher levels than even I thought we should after I noted some observations about growing with it. The main things I observed were:
1. Faster flowering times – up to a week faster finishing times with the same yield (ie; accelerated flowering and an increase in yield over cultivation time = defacto yield increase).
2. Bigger leaves (shade avoidance/photomorphogrnic response)
3. Longer internodes . . . except in the presence of UVA. Which, incidentally, is what I have always noticed about growing outdoors: sunlight may be 25% far red, but you don't see outdoor plants stretching in full sun because there is also UV, which is responsible for cell contraction (as opposed to cell expansion).
4. Happy, healthy plants – pretty much all the plants I've put under our high-far red spectrum have thrived. Especially shade-loving tropicals and ornamentals, like aroids.
I've been interested in UV ever since I noticed the difference in growing under Metal Haldie vs High Pressure Sodium vs comnbing the two at a ratio of 2 HPS to 1 MH. CMH came along later and pretty much combined the two.
But I also took note 20 years ago when some local hemp farmers I was freindly with started complaining about their Chinese seed stock showing elevated THC levels when grown under the Australian sun. The Chinese had tested their stock at <0.3% THC (below the legal limit), but once exposed to the higher UV index in Australia, those levels spiked to 0.5-1.0%.
We've since done our own tests that show a small amount of UV exposure does indeed increase cannabinoid levels, but it is not as simple as "UV or not UV" (little Shakespearean pun there, lol). There is some debate about the merits of UVA in relation to cannabinoids, but the most frequently cited experiments were not ideal – they only exposed the plants to UVA and UVB in the last 20 days of flowering and they also have very defined spectral bands. Still, there were more visible trichomes on the UV samples.
But I digress. This is perhaps not the thread for an in-depth discussion about UV or Far Red.
What you – and I suspect every other grower and/or light manufacturer wants to know – is, is it worthwhile sacrificing efficiency for spectrum?
My answer is yes. And there are several reasons for it:
* Broader spectra seem to grow healthier plants with fewer signs of nutrient lock-out (possibly transpiration or photo-oxidative stress related) and better quality in relation to yield.
* LED technology is advancing all the time. Efficiency will always improve – so you are always chasing your tail in that respect – whilst spectral balance has real benefits. My ultimate aim is to find the best spectra that works under most (typical) indoor conditions with cannabis as the primary crop and then pursue efficiency. And the reason for that is, we may find it hard to produce far red or cyan or 420-430nm violet now, but that may not always be the case. Once we have cracked the spectral code (so to speak), then it is simply a matter of sourcing the most efficienct diodes (as they continue to improve) to make that spectra.
* Lastly, sunlight is "true" full spectrum. LED is not. Sunlight may be dynamic – it's UV/RGB/IR ratios may change at different times, seasons, latitudes, altitudes, atmospheric conditions – but plants have evolved under FULL SPECTRUM. They have mechanisms for handling all sorts of radiant conditions that we don't truly understand yet, but are learning as we experiment. You are not going to discover the advantages of this spectrum or that spectrum by seeking the most efficient white phosphor/monochromatic red combination, because you are missing large parts of the spectrum (cyan for excample) or particular wavelengths altogether (far red, violet, UVA, UVB).
Spectrum vs efficiency is very much at odds at times – especially in relation to medicinal cannabis. Ultimately, producers want to sell either flowers or extracts. These two aims can compete when you are chasing dry yield over cannabinoid content or vice versa. It may well be in the interests of producers to grow the most cannabinoid content for the least amount of dry yield, as it makes processing easier and more cost-effiective.
So now it becomes a matter of, does a high-efficiency LED light produce more dry yield per joule of energy, or more cannabinoids per joule of energy, and how much extra energy is required to process each crop? If you could produce a spectrum that made trimming easier, that would save a lot of energy!
I guess in my case, there is no real mystery to producing a highly efficient LED grow light . . . but there is still plenty of mystery when it comes to finding the ideal spectrum that works for any given aim or crop. So that's what I'm mostly interested in.
But hey, that's just me.
