What is your recomended DLI levels?

I have been searching and reading for many months to find the optimum light levels of PAR and to find the happy medium for the DLI.

I have read university studies till I'm bleary eyed. Problem is university studies deal with veggies and supposedly the closest reference to cannabis is data for tomatoes.

I'm a newer grower in a small tent. In a non 420 friendly state. I have a Timber 300 watt kit I'm using.
I invested in a Apogee meter and have used online info to calculate DLI levels for 18/6 and 12/12 photo periods.
The best info I can find is that for veg the DLI should be around 20-22 and for flower 23-26.
My last grow before I had what little info I can find I'm pretty sure I cooked my plant. The light will run 950-1000 on the Apogee readings and I ran it full tilt even though it was about 2' above the plant.

I know different strains have different needs. Last one was Blue Dream Humbold seeds. This one is White Widow. I have the light at the top of the 7' tent now and am using a DLI of 22 in week 6 of veg. Already have some nice pre lowers on one and they look good.

I just can't find any cannabis specific light levels to shoot for that top growers use or the pros who sell to dispensaries.
Does this info exist in the cannabis world or am I barking up the wrong tree?

Do you have a data logger connected to the controller?



Anything from 20-30 moles per day will work, but the real improvements come when you start to play with different scales following the plant metabolism, not just on the vegetative phase and flowering phase..



You don't need a cannabis specific light levels, you just need to find a specific DLI map from where your genetics are.


Make sure you control the others environment factors otherwise you don't have stability to replicate on future grows..



Good luck!

I measure intensity at plant tops and midway down using the same meter as you.

With CMH and 18 hours of light it is 700-900 umol on top and 300 on the side. The budroom gets 13 hours at 900-1100 umol on top and 350 on the side.

12 band LED at 18 hours is 600-800 umol on top, 300 on the side. The 13 hour cycle is 700-900 umol on top and 350 on the side.

This has worked well for several years, less intensity is needed with 12 band LED than with CMH, the 6 band did not grow the plants well regardless of intensity.
A lot of factors come into play, the high number does not always work the best.

Thanks for the replies. I do not have anything elaborate to log data. I have the COB's turned down and when I flip in a couple weeks I plan on adjusting the light level accordingly and keeping a close eye on them. The DLI will be calculated from top of plant and I will track the data from the lower area as well.

I also plan on introducing a couple Reptisun 24" T5 lights as well. Still trying to decide when and how long to run them. I'm leaning to turn them on after 4 weeks for full light cycle.

I use the 48" Reptisun 10. The high output emits 54 watts, 5.4 watts UVB and 15 watts UVA. A Solartech Model 6.2 (www.solarmeter.com) is used for setup.
For reference, the sun puts 1/3 of 1% UVB to the leaves of plants, mostly in the middle of the day (259 microwatts at 66 degrees north).

The pictured meters are used for setting up spectrums and intensity levels. The increased efficiency repaid the $1000 purchase price within two years, since the meters are approaching ten years old it was a good investment.

Phaeton said:

I use the 48" Reptisun 10. The high output emits 54 watts, 5.4 watts UVB and 15 watts UVA. A Solartech Model 6.2 (www.solarmeter.com) is used for setup.
For reference, the sun puts 1/3 of 1% UVB to the leaves of plants, mostly in the middle of the day (259 microwatts at 66 degrees north).

The pictured meters are used for setting up spectrums and intensity levels. The increased efficiency repaid the $1000 purchase price within two years, since the meters are approaching ten years old it was a good investment.

Click to expand...

I am considering buying the uvb meter.
How long do you run them compared to regular lighting?

stewart169 said:

I am considering buying the uvb meter.
How long do you run them compared to regular lighting?

Click to expand...

Many different viewpoints on this.
I use low level UVB for the entire light cycle, others use a higher dose for a shorter time. Within limits both have similar end results.

The lower limit is 20 uw (microwatts) at the leaf, less has no perceptible gains. Maximum is 300 uw for a short time, more causes irreversible damage.
Some Indica plants did not care for over 200 uw without damage and many showed no gains at any level.
Sativa's fared better but since most plants are hybrids not developed for outdoor it is a trial by error to find the optimum.