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Thread: DLI for autoflowers

  1. #1

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    Default DLI for autoflowers

    Howdy.

    DLI: Daily Light Integral (DLI) is a measure of the aggregate amount of PAR light that a surface receives over the course of a day. It is a very useful metric to determine if a particular location receives sufficient amounts of light for plants to grow well.

    How much light your plants are getting over the course of 24 hours.

    Pluggin some numbers into a DLI calculator tonight and I'm starting to wonder if some of my late stage leaf problems are due to missing the mark on DLI.

    I've read you want to keep your flowering plants close to around 40 DLI. With the lights always on, that only requires around 475 PPFD. Looking at PAR charts for some common lights around the forum, I'm seeing readings of 475 way out in the corners of the tent and almost double that towards the center.

    So then I think, well if you don't need that much light then why not use something like a 300 watt in a 4x4 and crank it? Then I remember that I know someone doing just that and is having problems getting any size on their plants. So the small footprint must be the detriment.

    I guess I'm just spit balling here. My lights almost never go past 75% currently and even that might be too much at times. It's a balancing act at all times.

    For you auto growers:

    Are you full burning at 18 inches 24/7? Do you need to hang your light much higher?
    What's the consensus? I need to steal my wife's phone a bit to use her app but what if 60% power is where DLI is most compatible? Wouldn't that mean we're buying lights that are suited for photos but are overkill for autos?


    I plan to dig deeper but wanted to get your qualified (or unqualified I don't give a damn) opions on the topic as well.

    Cheers
    B


    "The footsteps of the farmer is the best fertilizer."

    Welcome to The Barnyard

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  3. #2

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    Well done for this thread Barney mate.
    This is everything I have been trying to determine for my previous and current auto grow.
    Been giving me a headache with my girls going to sleep after 18 hours.

    I got a HLG260 above one plant and feel stupid for it to barely be on half power, especially when I hear people on here saying that they have added extra lights and got them cranked up to near on full power.




    Sent from my SM-G950F using Tapatalk

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  5. #3

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    I run 2 x 260w HLG quantum boards 24/7 here, rarely get above 50% in my 4x4 (250-300w total) , but I only run 2 plants (usually, doing 4 this time). Gives me a really low light per square foot, Lux, par and dli number etc etc. More plants would require more light Dont need light in the corner if theres no plant there

    I stopped caring about the numbers and their ramifications when I grew my 6 foot tall 1.2lb auto. Her and her sister gave me a gpw of 2.1 (330w produced 770g)
    Last edited by Mac; 18-02-22 at 08:35 AM.

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  7. Default

    Quote Originally Posted by barney_b View Post
    Wouldn't that mean we're buying lights that are suited for photos but are overkill for autos?

    Cheers
    B
    I do believe most of us are using lights that are waaay 'overspec'd' for our needs Barney, when I purchased my first LEDs, the thinking was I'd rather have more than I need and dim them down than to be lacking or 'underpowered' if I wanted to upgrade to a bigger tent later on, and honestly, any of my future LED purchases would still be in this 'category', because I could upgrade my tent size later on down the road.

    Uniformity of light is also important..for example, we could hit numbers that are suited to our grow areas in "some" spots, but bad coverage of this light, I personally would be looking for better uniformity of light with two fixtures (as an example) dimmed down, and higher up with a better spread of the light.

    With DLI..this has come up before many times on the forum, with Gardro posting some good info on it, and it's given a lot of food for thought with autos for sure..because if true it could potentially mean we could drop daylight hours down to lower numbers than we think..


    For example, 15 hours of light @ 750 PPFDs would give us a DLI of 40.50 ..that could turn the whole " we can't go lower than 18 hours with autos" completely on it's head if it were to work perfectly fine


    Of course this could go into the extremes too, how about 11 hours of light for autos @ 1000 PPFDs giving us a DLI of 39.60 (obviously would need C02 supp)...now I'm not saying we SHOULD do this, but with what we know about DLI, then these numbers could work (on paper) lol.


    Now obviously there must be limitations to this, pushing to extremes need a very fine tuned environment where everything is perfectly balanced.


    It would really be interesting if tests were carried out to see how autos would react to these different daylight hours at the different PPFDs.. 16 hours of light @ 710 PPFDs (giving us a DLI of 40.90) would be an interesting one to start with.


    We also have the other factors to consider..how much DLI for the different stages of growth with autos?.. with small leaves there is only so much they can 'absorb' so how well would the lower light hours work for early seedling/veg?, again on paper they should be fine as long as we hit their max 'absorption'?

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  9. #5

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    Now see Ice you're on it. This all came from a Bruce Bugbee video series I've been watching/listening to. Some of his graphs got me thinking what you're getting at for experiments.
    This drawing isn't to scale. The DLI would be represented by the rectangles. If we keep all things even, we can draw some wild solutions to meet DLI requirements but at what cost? CO2 being one that you mentioned and ridiculous lighting being another.

    Click image for larger version. 

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    Shame gardro doesn't come around much any longer. I'm going to try and scour some of his posts. If I can find something pertinent I'll pop it here.

    Your thought on coverage jives well with what I've seen in my buddy's grow.

    This is great. Hope you folks continue to share insights.

    Cheers
    B

    Edit to say that so much of what I've learned about lighting requirements have been pointed at photoperiods. I hope one day we'll see stats that have hour cycles instead of stages of plant maturity. 12/16/18/20/24 for example.
    Last edited by barney_b; 18-02-22 at 07:26 PM.

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  11. #6

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    One thing to remember a lot of the lights we are using now a days are commercial grade.
    I think that may be one reason we are not running them at 100%. You really need the
    temps almost perfect and feed spot on ect., ect. Then you may get them up to 100%.
    I think Funky Dawg may have done a grow at that.

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  13. #7

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    Interesting convo that I can't add a lot to, but will say that even auto's get sleepy/droopy a couple of hours b4 lights out. That to me says that they have the ability to rest, thus posing the question, "is rest good for autos"? As to brightness of light vs duration, completely uncharted thought pattern for me, but will be watching thread as I find these topics quite interesting..

    -Domo

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    I like the coverage of multi panels running dimmed,I am guilty of the 'More is Better' thought I have to admit though,with both feed and lighting lol.
    I look at those dials and think to myself,what would Spinal Tap turn it up to?

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  17. #9

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    Further thoughts:

    The target of 40 DLI is too vague.

    Genotype/Phenotype
    Temperature
    Nutrients
    CO2
    Oxygen
    etc...

    All these factors are going to determine how high a DLI your plants can take. And since DLI is correlated with yield, it's almost a flex...
    "I got these girls pumped up to 53 DLI with no burn at all!"

    I can't find a good source, but I'm almost sure that heat plays a major role. The science overwhelms at the moment however.
    B

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  19. #10

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    Quote Originally Posted by Blue61 View Post
    One thing to remember a lot of the lights we are using now a days are commercial grade.
    I think that may be one reason we are not running them at 100%. You really need the
    temps almost perfect and feed spot on ect., ect. Then you may get them up to 100%.
    I think Funky Dawg may have done a grow at that.
    OH, yeah what Blue said. My B.
    B

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