Lighting wanna get yer geek on? Here's a scientific paper on cannabis and light for you.

[Olderfart]

I expect that this has been put up here already, but I don't recall running in to an actual copy of the paper, which is available in pdf form here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

Bottom line seems to be that cannabis, at least the strains tested, likes ~1500 ppfd and 30C best. The study measured short term response of plants, not optimum Daily Light Integral, so the applicability of it to grow light selection and use is still unclear to me.

Nonetheless, worth a coffee break browse if you want to get into a technical paper on the topic.

 

[Eyes on Fire]

Nice,thanks

 

[Death The Cultivator]

I expect that this has been put up here already, but I don't recall running in to an actual copy of the paper, which is available in pdf form here:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

Bottom line seems to be that cannabis, at least the strains tested, likes ~1500 ppfd and 30C best. The study measured short term response of plants, not optimum Daily Light Integral, so the applicability of it to grow light selection and use is still unclear to me.

Nonetheless, worth a coffee break browse if you want to get into a technical paper on the topic.

Though I have seen large plants reaching 1500 PPFD but it isn't economical when more cycles can be accomplished with SOG techniques. Maybe a consideration for greenhouse cultivators running co2 where seasons and weather vary.

It seems they were just measuring the responses at different peak values but they even admit that Cannabis L. Sativa is best growth in indoor climates similar to what they developed in. Co2 usage is going to necessitate higher ambient temperature and close monitoring of VPD.

Though there was nothing about yield or cannabinoids but 1500ppfd for a 12 hour cycle would be pretty close to DLI saturation at 64 with max co2

Imo, it could but still wouldn't be the most efficient way to accomplish anything for the indoor grower. Cost would be higher for what? 20-30% yield increase? That money could be better spent adding side and intra canopy lighting reducing the idea that there is a need to remove leaves for a myriad of reasons.

How much more yield could be achieved in a SCROG where the lowers aren't made bare and intra/side lighting with adequate airflow is accomplished. 6-800ppfd could still be used and maybe even a reduction in stem elongation with the right spectrum.

I'm just missing, thank you for the article!

 

[Olderfart]

Though I have seen large plants reaching 1500 PPFD but it isn't economical when more cycles can be accomplished with SOG techniques. Maybe a consideration for greenhouse cultivators running co2 where seasons and weather vary.

It seems they were just measuring the responses at different peak values but they even admit that Cannabis L. Sativa is best growth in indoor climates similar to what they developed in. Co2 usage is going to necessitate higher ambient temperature and close monitoring of VPD.

Though there was nothing about yield or cannabinoids but 1500ppfd for a 12 hour cycle would be pretty close to DLI saturation at 64 with max co2

Imo, it could but still wouldn't be the most efficient way to accomplish anything for the indoor grower. Cost would be higher for what? 20-30% yield increase? That money could be better spent adding side and intra canopy lighting reducing the idea that there is a need to remove leaves for a myriad of reasons.

How much more yield could be achieved in a SCROG where the lowers aren't made bare and intra/side lighting with adequate airflow is accomplished. 6-800ppfd could still be used and maybe even a reduction in stem elongation with the right spectrum.

I'm just missing, thank you for the article!

You are welcome Damian, glad it was interesting to you. As for me, the next grow will likely attempt to hit ~1000 PPFD at 18/6 by the time I am at flower, which should be roughly the high end of the DLI spec mentioned. I don't have a quantum meter, so I will have to do the best I can by converting from LUX. Not ideal, but maybe it will get me in the ballpark to see how the ladies respond. I was hitting them a bit too hard last winter, but still didn't do too bad in the end.

Happy growing Damian, and thanks for checking in.

 

[Mañ'O'Green]

Hey @Olderfart Thanks Good science there. For most of us home growers those environmental conditions cost more than the return value. Not to mention maintaining a Co² closed environment is difficult without running AC and/or dehumidifier. I have tried but did not really succeed.

I ran my last autos grow at 60 DLI and they did not like it. I am running my current Photos at 42 veg 39 flower DLI and they seem happy.

 

[Olderfart]

Hey @Olderfart Thanks Good science there. For most of us home growers those environmental conditions cost more than the return value. Not to mention maintaining a Co² closed environment is difficult without running AC and/or dehumidifier. I have tried but did not really succeed.

I ran my last autos grow at 60 DLI and they did not like it. I am running my current Photos at 42 veg 39 flower DLI and they seem happy.

Hi MOG, and thanks for the reply. Have you monitored DLI with autos in a grow that you consider good? Do you have a quantum meter? (trying to keep my jealousy under control )

I have no interest in going with CO2 and all the related mischief, but would like to try to put some numbers on the light regime that I am using. My inner geek is hard to tamp down at times...

Happy growing MOG!

 

[Mañ'O'Green]

Hi MOG, and thanks for the reply. Have you monitored DLI with autos in a grow that you consider good? Do you have a quantum meter? (trying to keep my jealousy under control )

I have no interest in going with CO2 and all the related mischief, but would like to try to put some numbers on the light regime that I am using. My inner geek is hard to tamp down at times...

Happy growing MOG!

No the first auto grow with the lights had other problems.

No, I do not have a meter. I just do the math. The information provided by the vendor is very thorough. There was a little difference in an independent test but not enough to change the numbers.

I have an inline watt meter on each of my 500w ChilLed GrowCraft so I can dial-in the watts used with the dimmer. This chart displays the information on 1 of the 6 light bars in the space (3 per Fixture). In order to achieve 39 DLI in 12 hours each light bar needs to run at 300 PPF . To produce that much light takes about 100w per bar or 300w per fixture or 600w total.

 

[Death The Cultivator]

You are welcome Damian, glad it was interesting to you. As for me, the next grow will likely attempt to hit ~1000 PPFD at 18/6 by the time I am at flower, which should be roughly the high end of the DLI spec mentioned. I don't have a quantum meter, so I will have to do the best I can by converting from LUX. Not ideal, but maybe it will get me in the ballpark to see how the ladies respond. I was hitting them a bit too hard last winter, but still didn't do too bad in the end.

Happy growing Damian, and thanks for checking in.

@elcoloan recently purchased an Apogee and was astounded at the difference between his LUX and Apogee.

Not to discourage you, I would watch the grow lol, but the benefits of the Emerson Effect are lost over 750-800ppfd but I believe that plant size has a certain degree of influence on the maximum DLI.

I believe the sun hits around 9-1500ppfd but plants are being hit with 300-799nm while the vast majority of manufacturers only cover the 400(barely) to 730nm(again, barely) range. I wonder how much yield could be achieved capitalizing on the Emerson Effect, supplementing the whole spectrum send providing side/intra lighting.

You know I swore I had seen the research paper before but I couldn't remember where. I first saw it on another forum and some members pointed out issues with the study

There are actually a few flaws, but none the less, its the only cannabis specific study with light intensity I have come across.


Flaws:
Only 1 type of cannabis species was tested (mexican variety)
Only red/blue light was used in the test, of specific wavelength, not full spectrum
The leaf samples were only given about 45 minutes of light, where photosynthesis peaks usually right before mid day sun.
The readings of PPFD were only on upper leaves using a closed device/system for measuring photosynthesis, but didn't take into consideration intra canopy measurements, or intensities within the intracanopy.
PPFD results were only measured within the range of 660-675nm. (not even the peak wavelengths for absorption)

Those are the flaws I found upon just quickly re-reading the study... so yes, there are quite a few flaws, but also we have to consider that there are very little light research studies done on cannabis in general, so the data that is gathered from this is useful, to some extent.


and after seeing your second hint, yea, they didn't use Far Red to create the emerson effect which would have influenced the results.

Nailed it.

The key was the red spectrum. Without Emerson, it could be anywhere from only 30-40% efficient which doesn't make it a direct correlation to a real world control. Plus with the hatred for monos, I thought it would have been quickly detected.

Also, it is just measuring the effect, not the overall outcome. Only the leaves were exposed for a short time frame and analysis performed.

But having said all of that, it does lead to other research. Keep in mind the study was done in 2008 using older led tech. Like I said a few times now, lots of opportunity to learn new things.

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Customers ask for high CRI LED for their plant growth projects at times, and sometimes this confuses us that why a well color rendered LED for human vision is also desired for plant growth? In order to understand this, we process relevant experiments and calculations for analyzing the reason...

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I found this article by a lighting manufacturer on b high cri - the last paragraph was the most important but I've heard that the reds over 600nm improved the SPD by various degrees when supplementing.

Curiously, most lights have individual SPDs that have to be measured with a spectrometer to give an accurate conversion of ppfd to LUX but lux meters don't capture the full spectrum that we want for our needs. Think an Apogee is expensive, spectrometer are in the 2k+ range.

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This is a fun topic

 

[Death The Cultivator]

No the first auto grow with the lights had other problems.

No, I do not have a meter. I just do the math. The information provided by the vendor is very thorough. There was a little difference in an independent test but not enough to change the numbers.

I have an inline watt meter on each of my 500w ChilLed GrowCraft so I can dial-in the watts used with the dimmer. This chart displays the information on 1 of the 6 light bars in the space (3 per Fixture). In order to achieve 39 DLI in 12 hours each light bar needs to run at 300 PPF . To produce that much light takes about 100w per bar or 300w per fixture or 600w total.

View attachment 1246168

View attachment 1246169

That's money well spent!

 

[Mañ'O'Green]

That's money well spent!

I am well pleased with the results so far in this grow.