So, if I am on day 10 of the grow I should be targeting a DLI of 15.
My question comes at this point.
To achieve a DLI of 15 I can run for 18 hours at 230 ppfd, or I can run for 20 hours at 210 ppfd, or any other combination of time/ppfd that satisfies the equation.
If I am observing DLI, then does brighter for a shorter period vs dimmer for longer make any difference to the grow? DLI of 15 is a DLI of 15, right? Shouldn’t matter either way???
One thing about your chart to think about is that transition to flower when flipped one would think it may be more ideal to provide a higher light level or at least make it happen quicker once 12/12 vs the slow rise over three weeks they suggest.
DLI is more accurate to judge how much light a plant is getting over the course of a day. I am not aware of anyone figuring out if shorter or longer days are better at the same DLI.
I have to find where I read recently that once a plants DLI requirement is met anything above and beyond, in terms of light time or intensity, is almost a waste in terms of electricity used. The article states, don’t quote me, it’s almost a point of diminishing return.
So I got to thinking, , outdoors upstate ny I think 16 hours of during summer solstice and plants are doing great. I have to check my DLI but I’m running 16 hours with my intensity at 4 and the plants love it. I like to play around, take notes and compare.
I’m running 225 PPFD at 24/0 since starting the seeds and so far so GREAT! The dome and 4" pots I use to cover them as they start all would drop the PPFD’s so each removal is bumping up my DLI I’m realizing.
This is super interesting though and I need to read up on DLI more.
Figure 2 shows the DLI topping out at 45 and that seems way too high. I believe that Dr. Bugbee’s testing showed that DLI 35 was about as much as cannabis can utilize in the absence of extra CO2. I’ve had best results maxing out around 25 DLI during flowering. Much beyond that, “Beware the Dreaded Nanners!”
I’m wondering if there is any energy savings to be had in playing the Hours/PPFD game. The total amp hours used by your lights is a product of intensity over time. So if you turn up the PPFD and run it for less time, or turn it down and run it longer you’ll likely use the same amount of energy. Basically DLI measures the amount of usable energy and whether you deliver it quicker or slower shouldn’t matter much to the plant OR your energy bill. There may be something I’m not considering tho…
Nice topic @MrWizard, I like the way you think!
-Grouchy
What may come into play here is the efficiency of both the power supply and whatever outputs the light. With a LED it’s possible that the driver is less efficient at a lower output, but the LEDs being driven may actually be more efficient with that lower output. If you factor for that in DLI calculations you may be able to figure out that one combination of settings is more efficient than the other. However, there is no constants for these as far as I know and each driver/LED combo will need different numbers calculated.
Yeah, that would give you the most accurate real-life numbers and be the easiest to calculate. The product sheets for drivers and LEDs usually give enough info to calculate this as well. So in absence of a watt meter those product sheet numbers should give you a rough idea too.
, outdoors upstate ny I think 16 hours of during summer solstice and plants are doing great. I have to check my DLI but I’m running 16 hours with my intensity at 4 and the plants love it. I like to play around, take notes and compare.
