Lighting What's the best lighting cycle for autos - 24/0, 20/4 or 18/6

[WildBill]

24/0 worked really well for me for my first grow, over 1/2 kg of dried/cured weed and over 1/2 kg of fresh frozen trim/popcorn, and that's not counting anything I smoked for over 4 weeks, 300watts from 2 x TS1000 Mars Hydro in a 2x4x6ft tent also from them if that makes any difference.
View attachment 1289867

Sure worked well, but did you spend money on the power needlessly?

 

[JSH1973]

Sure worked well, but did you spend money on the power needlessly?

I think the only answer to that is YES when it comes to 24/0 light cycle, anything over 18 hours you're paying a good big extra for small extra gains that aren't even guaranteed, we'll that's my impression of it anyway, after my current grow I'll be switching to 20/4 or 18/6 with my Autos.

 

[NorthernLights_420]

24/0 worked really well for me for my first grow, over 1/2 kg of dried/cured weed and over 1/2 kg of fresh frozen trim/popcorn, and that's not counting anything I smoked for over 4 weeks, 300watts from 2 x TS1000 Mars Hydro in a 2x4x6ft tent also from them if that makes any difference.
View attachment 1289867

Happy smoking there

 

[automan2]

Over the years I've grown under different lights, different places and different schedules...first with the hopes of massive yeilds, then it was fire quality...then it was best quality at lowest price.
I did find more light hours increase yeild but also increases everything else...time, nutes, environment control & most of all ENERGY COSTS.
Long term data...MY OWN....tells me the % increase in yeild does not equal the % increase in energy cost...but quality stays pretty much the same.... End result for me..I stopped running races... grow everything 12/12 after 24/0 for 3 week veg and have for years....perpetually running 4-6 strains in all stages of growth.
Might have lost a few grams but am happy with a full 12 hr rest time (for me too) and lots less cost.

 

[pop22]

I think we need to start taking DLI into consideration. There is literally a limit to how much light a plant can use per day. So how long to run your lights should be predicated on how powerful your lights are. New information say Cannabis can withstand up to 2000 micromoles, however, that does not mean they can take it for 24 hours straight. That figure is based on the sun at noon at the Equator. That's where DLI comes in. It's a measure of how much light a plant can use in one day. At a certain point, plants have mechanisms that reduce the amount of light entering leaf cells, and can also halt photosynthesis, called photo-inhibition. Science thinks the DLI of Cannabis is 60-65.

DLI is the total number of photosynthetically active radiation (PAR) photons incident on an area over the course of a day. DLI is a function of both the intensity and duration of the photosynthetic light falling on the target over a day and is most commonly expressed as moles of light per square meter per day or mol m-2 d-1.

DLI = PAR * (number of hours) * (3600 s hr-1 ) / 1,000,000 µmol

PAR is the instantaneous measurements in units of µmol m-2 s-1, number of hours is the total number of hours the light is on during a 24 hour period, 3600 is the number of seconds in an hour, and 1,000,000 is the number of µmol in one mol. For example, if the instantaneous PAR from a specific light source is 600 µmol m-2 s-1 and the light is on for 12 hours, the DLI is 25.9 mol m-2 d-1:

DLI = 600 µmol m-2 s-1 * (12 hours) * (3600 s hr-1 ) / 1,000,000 µmol = 25.9 mol m-2 d-1

Calculation of DLI from an instantaneous PAR measurement relies on the assumption that the light source is constant while it is on.
So we may not know the PPFD of our light but there are sources, other than the manufacturer, of that information, such a Migro on youtube, where the measurements are taken in a real world environment.

I calculated my DLI for the tents with Diablo lights, running at 400 watts and producing 1100PPFD, for a 20 hour period, DLI= 79.2, which is far in excess of it's needs. I can either dim my light or shorten the lights on period. 16 hours would give me 63.3 DLI I'm thinking a combination of some dimming and a shorter, 18 hour day might be ideal. I'm going to experiment with this when my new LED drivers are installed.

i'm considering buying a Qauntum PAR/DLI meter. It's a bit expensive for my budget but I can sell it when I'm done with it.

https://www.precisionusa.com/mStore...er-uom=EA&warehouse-id=1&item-number=48035650

 

[WildBill]

pop22

I totally agree.
If I build a room in my shop, a meter will be in the budget.

I might be forced to get one sooner, If I win that Mars SP6500 monster for my 4x4 tent! LOL!

 

[NorthernLights_420]

I think we need to start taking DLI into consideration. There is literally a limit to how much light a plant can use per day. So how long to run your lights should be predicated on how powerful your lights are. New information say Cannabis can withstand up to 2000 micromoles, however, that does not mean they can take it for 24 hours straight. That figure is based on the sun at noon at the Equator. That's where DLI comes in. It's a measure of how much light a plant can use in one day. At a certain point, plants have mechanisms that reduce the amount of light entering leaf cells, and can also halt photosynthesis, called photo-inhibition. Science thinks the DLI of Cannabis is 60-65.

DLI is the total number of photosynthetically active radiation (PAR) photons incident on an area over the course of a day. DLI is a function of both the intensity and duration of the photosynthetic light falling on the target over a day and is most commonly expressed as moles of light per square meter per day or mol m-2 d-1.

DLI = PAR * (number of hours) * (3600 s hr-1 ) / 1,000,000 µmol

PAR is the instantaneous measurements in units of µmol m-2 s-1, number of hours is the total number of hours the light is on during a 24 hour period, 3600 is the number of seconds in an hour, and 1,000,000 is the number of µmol in one mol. For example, if the instantaneous PAR from a specific light source is 600 µmol m-2 s-1 and the light is on for 12 hours, the DLI is 25.9 mol m-2 d-1:

DLI = 600 µmol m-2 s-1 * (12 hours) * (3600 s hr-1 ) / 1,000,000 µmol = 25.9 mol m-2 d-1

Calculation of DLI from an instantaneous PAR measurement relies on the assumption that the light source is constant while it is on.
So we may not know the PPFD of our light but there are sources, other than the manufacturer, of that information, such a Migro on youtube, where the measurements are taken in a real world environment.

I calculated my DLI for the tents with Diablo lights, running at 400 watts and producing 1100PPFD, for a 20 hour period, DLI= 79.2, which is far in excess of it's needs. I can either dim my light or shorten the lights on period. 16 hours would give me 63.3 DLI I'm thinking a combination of some dimming and a shorter, 18 hour day might be ideal. I'm going to experiment with this when my new LED drivers are installed.

i'm considering buying a Qauntum PAR/DLI meter. It's a bit expensive for my budget but I can sell it when I'm done with it.

https://www.precisionusa.com/mStore...er-uom=EA&warehouse-id=1&item-number=48035650

I do 18/6 and agree with this statement

 

[Couch_Lock]

My HLG no longer dimms, its worn out. I kinda feel sorry for my baby autos, they gettin pelted 24/7

Weather forecast is warmer next week, I hope to be able to shut down 3-4 hours a day. I keep the light a good 35 to 39 inches away but all this brightness doesn't seem to help the vegging. That period is almost over, Im seeing tiny prebudlets......oldest plants are 25 days old, two of them are 22.

The Timber 2 VL is not enough wattage by itself.....and the CMH seems to go through bulbs like crazy, I'd rather not use that. Next grow I'm gonna have to buy a few Phillips cmh bulbs again. Beats droppin another $700-900 on a light.

 

[sidfinch]

I think we need to start taking DLI into consideration.

Most definitely. I can tell you from experience that if you put a flamethrower in a 4x4 you're going to learn about DLI sooner rather than later.

What I've researched says you want a DLI of 40 max unless you're running CO2.

I've been using a basic LUX meter and conversion tools from my light manufacturer (HLG) to determine my PAR/DLI. I've cross referenced with an iOS app Korona and between the two it's close enough for me. I'd love a real apogee quantum meter but it's hard to justify $600 for it.

 

[pop22]

I'll give you a deal when I'm done with the one I plan to order next week. My current light are long term so once I have the data I need I won't need the meter again.

pop22

I totally agree.
If I build a room in my shop, a meter will be in the budget.

I might be forced to get one sooner, If I win that Mars SP6500 monster for my 4x4 tent! LOL!