Dli And Photoperiod

[crimsonecho]

Hellllooo farm,

Recently i have been having troubles with my plants. Some deficiencies that shouldn’t be and couldn’t be fixed. The leaves that were getting the highest intensity of light were getting yellow and the sugar leaves were just losing their colour and getting spots. Couldn’t fix it so i started to blame my new fixture :D

Now 500w of cree cobs in a 2x4 area is a little much, i’m aware but i didn’t think it will cause any problems since i was getting 70K at the closest readings. But i think i overlooked the dli and the actual ppfd. A quick search of the web shows that a cree 3000K 80 cri led has a conversion factor of 0,0149... this is the number to be multiplied by the lux reading you’re getting. It is QER/LER. In this case 328.322735/4.867319958 which roughly corresponds to 0,0149. This does not 100% apply in my situation as i have 4000Ks and 6500Ks in there, but for arguments sake lets say that it does (it will be a good estimate).

Now 70K x 0,0149 equals 1043 umol/s. This is the amount of light that was hitting the tallest tops and the yellowing tips. 1000 umols is actually a good amount of radiation for plants imo. Not so much that it would cause bleaching or anything. Just a tad over the optimum ppfd requirements of these type of very high light plants. Which is somewhere around 600 to 800 on different sources for high light plants. (*edit; in the light of new research i stumbled upon 1500 umol/s is decided to be the optimum but with which strains remains a mystery. Just Cannabis Sativa L.) But it can be pushed with co2 supplementation i’m sure.

Anyway back to the topic at hand. So, 1000 umol should be fine because we growers believe that if theres anything cannabis wants is more light. But i’m only getting these deficiencies on the outer leaves that are directly under the intense lights. So i’m pretty sure i oversaturate them thru their designated photoperiod. And another little calculation proved that i was giving 40+ moles per day to the upper branches. Here is the calculation i used (i actually used a dli calculator on the web :D but this is their formula).

((60 sec/min)*(60 min/hr)*(12 hrs/day)*(PPFD))/1 million

Considering a fully mature tomato needs about 30 moles per day to provide maximum yields, 40+ moles is just too much for these which are in 2 gal pots without co2. So i dialed it down to 25 moles at the tops and 20 moles at the shorter plants tops.

Now without moving further, the issue i have still havent resolved because its been just a day but the calculations seem spot on and i just wanted to share these figures and the process i went thru to end up coming to this conclusion and the battle to correct it.

Finally, the question on my mind is, which would be better, 12 hrs on 2 bars and 590 umol/s which would be 25 moles per day or 8 hrs using 3 bars and 1040 umol/s which would be 28 moles per day. Which one would you go with?



https://www.apogeeinstruments.com/conversion-ppfd-to-lux/
https://www.specmeters.com/assets/1/7/2013_-_DLI_Greenhouse_Tomato1.pdf


*some links i cannot give because they’re from other forums.

 

[MidwestToker]

Sounds reasonable, but I myself don't rely on the numbers them self. I go by what the plants tell me. Not that I'm dissing the science, just that there are too many variables from garden to garden to actually put a certain number.

 

[crimsonecho]

Sounds reasonable, but I myself don't rely on the numbers them self. I go by what the plants tell me. Not that I'm dissing the science, just that there are too many variables from garden to garden to actually put a certain number.

They are telling me something is wrong and i think its the lights. They’re just too bright and plant just gets pulverized with 40+ moles per day. As i said some plants may like it even. Sativas should love it for example but this one doesn’t i think. Co2 would help also which i don’t provide.
So afterall what is it? 8hrs or 12hrs? The dli will be higher with 8 hours :). Shorter photoperiod but more photosynthesis so shouldn’t diminish yields in theory.

 

[crimsonecho]

Sounds reasonable, but I myself don't rely on the numbers them self. I go by what the plants tell me. Not that I'm dissing the science, just that there are too many variables from garden to garden to actually put a certain number.

It was literally like growing cannabis in august in arizona at an unshady spot. Now thats a lot of light.

Now its kinda like Seattle in there :D

 

[MidwestToker]

They are telling me something is wrong and i think its the lights. They’re just too bright and plant just gets pulverized with 40+ moles per day. As i said some plants may like it even. Sativas should love it for example but this one doesn’t i think. Co2 would help also which i don’t provide.
So afterall what is it? 8hrs or 12hrs? The dli will be higher with 8 hours :). Shorter photoperiod but more photosynthesis so shouldn’t diminish yields in theory.

But are you actually growing cultivars that are acclimated to the intensity of outdoor lighting or cultivars that through generations have been raised and propagated by HID lighting. Just my experience with plants morphological ability to adjust and change to their environment factors over time in that environment.
Good discussion anyways, good talking with knowledgeable growers.

 

[crimsonecho]

But are you actually growing cultivars that are acclimated to the intensity of outdoor lighting or cultivars that through generations have been raised and propagated by HID lighting. Just my experience with plants morphological ability to adjust and change to their environment factors over time in that environment.
Good discussion anyways, good talking with knowledgeable growers.

I agree on these cultivars having been adapted thru generations to the high light intensities and they are high light plants to begin with but do you think they supply over 40+ moles per day in most setups? Plus the conversion factor for most hid lights are lower than leds. Only cmhs compare.

https://www.apogeeinstruments.com/conversion-ppfd-to-lux/

And i agree that some plants will deal with it or thrive in it. Last grow my dinachem was getting 90k lux on some branches and they turned out fine. Was still getting a bit light stress now that i look back but it was 90K. Way too much. But all in all i can say, it thrived in that environment in 5 gals organic living soil. These in 2 gals they struggled i think.

Next run i’ll do 3 bars again but will use 7-10 gal sips and living mulch to keep the soil a bit cooler too. In that setup i think they will be able to handle much more and produce much more. But this run, with lights being new there is a learning curve and starting with 2 gals just made it kinda harder but i couldn’t fit 6 5 gals there and have room for my veggies :D plus there is such a thing as too much weed :D

So i’m just trying to find out which way would be the better route. 12hrs of constant relaxed sunbathing or 8 hrs of Icarus flying to the sun deal :D

Giving extra dark period could shorten the flowering probably but would there be any benefits when it comes to trichomes? I know the active compounds degrade under light and replenished constantly but would giving a higher intensity light for a shorter duration and then letting it replenish in the dark give better results or not? Or how about the density of the buds? Same buds with higher dli and ppfd but longer dark period or lower dli and lower ppfd and longer light period. Which buds would be the best?

Mindfuck :D

 

[MidwestToker]

A lot of variables as I said earlier. First most cannabis plants are lucky to get 5-7% of their inputs to turn into plant matter. Where, if my memory serves me right, tomato plants are 10-12% efficient in turning their input into plant matter so almost double in term of plant matter production per units of input compared to cannabis. Hence why you can feed a tomato plant 2.1+ ec and not skip a beat, feed a cannabis plant 2.1 ec and we both know what'll happen.

Over all, and from my experience, best trich responses happen in lower light intensities the last 2 weeks of flower.

 

[crimsonecho]

A lot of variables as I said earlier. First most cannabis plants are lucky to get 5-7% of their inputs to turn into plant matter. Where, if my memory serves me right, tomato plants are 10-12% efficient in turning their input into plant matter so almost double in term of plant matter production per units of input compared to cannabis. Hence why you can feed a tomato plant 2.1+ ec and not skip a beat, feed a cannabis plant 2.1 ec and we both know what'll happen.

Over all, and from my experience, best trich responses happen in lower light intensities the last 2 weeks of flower.

Sure lots of variables and i’m sure, again, the little pots didn’t help with my case. Good point on efficiency of creating plant matter, not well versed on the issue, i’ll look into it. EC is not something i really look into much.

I see there is a research on the subject and in that research 1500 umol/s has been found to increase photosynthesis still. So again 1000 is not a problem on its own but coupled with under nourishment and probably the genetic factors in this case, led me to believe that this can be light stress.

So, you feel softer light and shorter dark periods are the best. Kinda think the same. I just wonder if it’d get bigger with 8hrs light because of the increased dli. It just makes me wonder but then again, forcing it to endure 8 hrs of light a day can cause her to finish faster and would probably cost me in the yields department.


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

 

[MidwestToker]

Sure , but that's not a complete study to me. No where do they state a difference in what is actually happening inside the plant. Increased gas exchange from the stomata could be from the increase in temps and not directly related to carbon fixation or other process's that occur in the plants.

 

[MidwestToker]

Did you read the PDF ? Notice what type of lighting they used and the spectrum?
(Model LI-6400-02; light emitting silicon diode; LI-COR), fixed on the top of the leaf chamber and were recorded with the help of quantum sensor kept in range of 660-675 nm, mounted at the leaf level.
Blue and red LED's or the old blurple's. Not white full spectrum lights.

 

[crimsonecho]

True its not a complete study but its a guideline. You can adjust according to plant response.

Well anyway, this is actually what i don’t want this thread to turn into. A never ending debate about ppf, ppfd and so on. Because, i’m well aware of the pitfalls of following a schedule or a guideline religiously. Never happened to me because i try to use common sense and care but i’ve seen it. For me, i don’t actually care what the study says, 1500 is just too much because i don’t need 5 lbs of weed just an lb could sustain me for a year. So the investment to get a fixture that emits 1500 umol/s that would cover 4x4 perfectly and providing co2 and keeping the temps at a constant 30 etc etc. is just useless work. If you have the means yeah i do believe if you can do all these and get a good feeding schedule dialed in, you can get the most out of your plant, given that cultivar is well adapted to such environment (they can adapt fairly quickly anyway, with clones you will be ready to go) and get killer yields. This is the science, no use in saying i don’t utilize science, everyone does so why utilize some parts of it and choose to dismiss the rest. Anyway whats optimal for me is to get good, fragrant buds that are sticky as hell and healthy and delicious as heaven (atheist here). So i don’t need that much yield. Also i dont really compare the tomatoes to cannabis because each plant is unique but a high energy plant to high energy plant comparison, they got similarities. 30 moles per day should be enough for me at this point.

What people are forgetting is that there isn’t a single way to grow and everyone grows their shit differently because everyone has different needs. I see this on every advise given on the forums. I will never grow like a commercial grower because everyone of these commercial guys keep saying they grow the best stuff and they’re the champ and all but truth is, i’ve never smoked anyhting as fragrant and tasty as my own shit, not in amsterdam, not in any parts of Europe (true there may be some sentimental bond there and the handling after harvest is another issue with commercial weed, tumblers, trimmers, transportation etc etc. but i’ll say top 3). So where are all these great growers?

The thing is we have needs and we grow according to those needs. A commerical grower needs to get the highest yields as quickly as possible while spending as little as possible. I have the need to produce quality for myself. So i don’t need the brightest lights or co2 supplementation. Just need happy plants in happy mediums.

Basically the question on my mind is would 28 moles thru 8 hours be better than 25 moles thru 12hrs. I’ll probably turn on the veg bar again. I’m an impatient and quite excitable fella so i can’t hold out for much but i need them to pick up the pace first. Since i transplanted it into a 5 gal, i hope the problems will resolve on its own and it’ll be able to grow vigorously again. Well not much vertical anymore but a good weight gain would be nice.

Really the worst kind of stoners are a couple of nerdy stoners like us :D

 

[crimsonecho]

Did you read the PDF ? Notice what type of lighting they used and the spectrum?
(Model LI-6400-02; light emitting silicon diode; LI-COR), fixed on the top of the leaf chamber and were recorded with the help of quantum sensor kept in range of 660-675 nm, mounted at the leaf level.
Blue and red LED's or the old blurple's. Not white full spectrum lights.

Yeah but umoles are umoles. Again, a guideline, not something to set your environment to.

But i do see they used a mexico originated cultivar. So its probably more than properly adapted to high ppfds.

 

[MidwestToker]

Yeah but umoles are umoles. Again, a guideline, not something to set your environment to.

But i do see they used a mexico originated cultivar. So its probably more than properly adapted to high ppfds.

I'm not against Science, it just most research focuses on single inputs or only a few processes during their testing. If life was only that simple, we would all have it made.