How light spectrum affects nutrient use in plant tissue...

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Thanks! I do like the research papers when they are recent since they are now more specific about cannabis. If you like a more descriptive video sort of delivery - there are these videos at https://www.apogeeinstruments.com/videos-and-tutorials/

So the presenter is a guy ( shit you not - Dr. Bugbee ) who tends to pound in the concepts, he goes there about how terms seem mixed and confusing. I've noticed that at the ends of these videos - they have spliced in some extra minutes where he gets specific about spectrum effects with cannabis. Apparently they have a license to do cannabis research that makes this a bit better than the usual academic exercise of extrapolation to shit they really aren't sure about.

Dr. Bugbee does seem to have the appearance of being like, really smoked out. I like how he tends to explain the background history of the science involved.
 
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This video talks about the topics in this thread (nutrient use) Toward an Optimal Spectral Quality for Plant Growth and Development
Holy shit that one scratched an itch I've had for a while. Seeing the actual effects of different light temps on cannabis photosynthesis just made a bunch of things fall into place.

I started in June of this year (with no indoor growing experience) under a 5k LED that I started growing with, going off of a bit of misguided research. The plants took forever in veg, grew oddly, and were very susceptible to light shock. I started adding some 2700-3500k cfl's and there's been a significant rebound in vigor, especially with the younger plants. Now I actually understand why!

So now are the only "full-spectrum" lights the ones with far red and UV?
 
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@Kanzeon Welcome to the farm. I see you took the red pill.

If you parse the video carefully - you may note that Far-red spectrum is useful at flip ( 12 hour regimen ) to stimulate early, robust flowering. I would suspect this may be the Fall light spectrum ( recall, we want to mimick the normal solar exposure, low angle sun ) that assists in triggering the natural ripening process.

I've been looking at this spectrum issue ever since the emergence of LED light sources for growing. I've worked with LED and other light source technologies since the 80's. My biggest frustration has been with looking at static spectrum charts rather than actual spectrum data from MY light sources. Light sources age, degrade and shift from the first time power is applied and I can assure you that any source spectrum the vendor shares is probably not what the source provides over the expected service life of the source. Lab-quality instrumentation for measuring spectrum is expensive, even as used equipment.

Fortunately, the germans have been really busy working on devices that solved most of the problems, including cost. I built a prototype based on the hardware and some open-source code that gives me the data I wanted - in a easily consumable format. I'll share the output in my next post.
 
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@Kanzeon Welcome to the farm. I see you took the red pill.

If you parse the video carefully - you may note that Far-red spectrum is useful at flip ( 12 hour regimen ) to stimulate early, robust flowering. I would suspect this may be the Fall light spectrum ( recall, we want to mimick the normal solar exposure, low angle sun ) that assists in triggering the natural ripening process.

I've been looking at this spectrum issue ever since the emergence of LED light sources for growing. I've worked with LED and other light source technologies since the 80's. My biggest frustration has been with looking at static spectrum charts rather than actual spectrum data from MY light sources. Light sources age, degrade and shift from the first time power is applied and I can assure you that any source spectrum the vendor shares is probably not what the source provides over the expected service life of the source. Lab-quality instrumentation for measuring spectrum is expensive, even as used equipment.

Fortunately, the germans have been really busy working on devices that solved most of the problems, including cost. I built a prototype based on the hardware and some open-source code that gives me the data I wanted - in a easily consumable format. I'll share the output in my next post.
Thanks! This place is amazing. DEFINITELY looking forward to seeing the details.

How does time affect spectrum accuracy with LED's? Do they tend to have a narrower spectrum over time?
 
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Do they tend to have a narrower spectrum over time?
That is one of the benefits of LED tech - as long as you aren't mistreating the device ( too hot, too much current ) you get the photons you were looking for - they don't shift their spectral characteristics like metal vapor lamps. If you ran a commercial farm with any of the metal vapor light sources, you get a certain lifetime that is part of your process - you change the lamps at least once a year because of lamp aging. Even with the best of breed - the lamps fade.

With LED - the failure mechansims are different. These tend to be latent packaging issues or contamination during the manufacturing process, assuming they aren't being run at or over the design limits. If the design is conservative - you should see 5-7 years of relatively consistent performance. Longer life than that usually requires luck, good environmental conditions, expensive parts or other special considerations ( thinking about space-craft that may have a 50-100 year lifespan ). Solder cracks can ruin your day.
 
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This is the raw spectrum from my LED lamps. They emit broadband white light - because the actual light is produced by a phosphor.



Screen Shot 2019-12-28 at 11.35.09 PM.png


This is the spectrum from the above lamps with UVB/UVA lamps added.


Screen Shot 2019-12-28 at 11.36.35 PM.png
 
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So this consists of a simple arduino program that reads the sensor ( 18 channel spectrometer ) and a python program that draws the graph in real time.

Lets just say I'm pretty happy - except for the gap in UVB (a limitation of the spectrograph) as my UVB lamps are unfortunately - metal vapor based. They will need to be monitored for lifespan and replacement. I'm working on that problem.
 
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Holy shit that's awesome. I'm super jealous, especially with that arduino setup.

So if LED's essentially work within their designed spectrum from start to failure, does it then follow that a number of less expensive COBs in e27 sockets over a broad area and set from different angles onto a grow space, would produce the same general grams:watts ratio to the same (or similar) led's mounted closer together on quantum boards on similar spectrums?
 
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Aaand this is where things usually run into the weeds. Most of the sources you mention are not standards that can be compared. While photons are pretty generic - their spectral characteristics aside - this becomes a question that starts to really depend on the subject strain. YMMV and all that - mostly because the specifics are not characterized to some level of certainty.

Every strain has different requirements - based on genetic pre-disposition. One of these requirements is DLI - the Daily Light Integral - how many photons are available in a growth day. This measurement is commonly used in production, greenhouse optimization to deliver a crop in a certain number of days. This regimen also applies to cannabis - I've often compared to growing tomatoes ( another high DLI plant ).

THIS is why we have the farm - to compare notes and observations. It's pretty much:

showme.jpg
 
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THIS is why we have the farm - to compare notes and observations. It's pretty much:

View attachment 925179
Exactly. Plus the growers here aren't shy about offering constructive criticism, which is awesome.

To this end, my next light purchase is almost definitely going to be E27 COB bulbs ranging from 2700k to 4000k.

Something along THESE lines.

So Bruce Bugbee himself recommends about 1000 PPFD for indoor cannabis plants. That's the end goal. That dude knows his shit.

The design of quantum boards is awesome for a lot of things, but they distribute light in one general direction- down. My canopy isn't and won't be even (I'm too much of a tinkerer and like to grow a bunch of different strains), so a level light source above the plants means that the top buds get the majority of the full-spectrum light, which then degrades in quality as it bounces around the space.

My theory at the moment is that a number of smaller LED bulbs placed above the perimeter of the general canopy and directed at intersecting angles across the grow space could potentially be a more efficient solution in terms of both electricity and yield than adding another quantum board. More light = bigger buds, right? With the lights at an angle, the photons coming from them can theoretically be used by the plant to greater effect since they're exposed to more of the plant's surface area without hitting anything else.

Those lights above claim 700 lumens per 15w led bulb (5 diodes per), but they don't say at what distance that was measured from. When putting them up, I'll measure so that they're roughly 70,000 lux (where the risk of light shock rises) to the canopy, but mounted at 45-60 degree angles, which works out to roughly 1000-1200 PPFD with the estimated combined bulb spectrums.

Am I missing anything?
 
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