24/0 or 20/4

[McDee]

I have done both, havent noticed a difference. I think 24/0 they may finish a little earlier depending on strain, just a feeling no science. I run 24/0 in the winter just for extra heat, but go back to 20/4 when temps go back up.

 

[MidnightSun]

24/0

 

[nekvt]

I run 24 hours a day.

 

[Mizzo81]

I do 19/5 because I set my timer that way on accident and have been too lazy to reset it.

The first year this is how and why I ran them switched to 24/0 now back at 21/3 for some savings.

 

[Waira]

If running 18/6 going to 24/0 is an increase of 33% will the yield increase 33% ? If running 24/0 and decide to 18/6 a reduction of 25% will the yield reduce by 25% ?
+\- cost of electricity or just run 19/5 to ne odd

:smoking: It's not a linear relationship like that,... Last consensus I recall it was very conditional when it's truly worth it, mainly that last 4hours, fastly diminishing returns... Best positive example I've seen is with hydro grown monsters,....Grey Bear, a former staff had insane yields, somehow got consistently longer veg times out some of the strains he ran, and epic blow-up during stretch too! Always, 24/0,...
...I can say from what I see in Sick Bay that often as not, just because you can, doesn't mean you should,.... 24/0 under hammering light (too much, even if not showing the typical physical signs of it) seems to be causative of other issues: localized defc.'s, VPD issues, foxtailing, nanners,... not always, not consistently, but as a general trend I've noted anecdotally,... Seems strain dependent too, or maybe more accurately the Sativa : Indica balance? Point is, many can take it technically, but it's not always worth it,.. I've tried 24/0, and 20/4, 18/6,... most problems, and no significant yield improvement was noted under 24/0 vs 20/4, plus the only hermies I've had occurred under that sched'. as well,.... Often, it's a micronute issue, but seen Ca and Mg blow ups too.... problems fixed faster and better when reduced back to 20/4... It's not that the plant "needs the rest" technically, but forcing the equation, if you will, can trigger them, magnify existing ones, and be more difficult to correct sometimes,....

 

[Mizzo81]

Well said @Waira

 

[Son of Hobbes]

Food for thought:

There are two important qualities to look at in PAR light for growing, one is the amount (what we would consider intensity) and the other is spectral light quality (which is referring to the spectrum the light is producing, often noted with spectrum graphs that you may have seen while looking at grow lights.)

PAR is quantified by PPFD, measured in micro-mols per second (μmol/s), indicating how many photons in this spectral range fall on the plant each second.

PPFD (Photosynthetic Photon Flux Density) measures how many photons (PAR) are hitting an area per second.

If you’ve ever looked up grow lights of any kind, nearly all of them have some sort of information on the PAR/PPFD, usually PPFD is a coverage chart that shows the PPFD rating at certain heights and spreads of the light over a certain area of coverage.

Depending on the type of lighting and how it’s mounted, PPFD can be fairly homogenous (spreading the light out equally, giving near equal coverage in the recommended space for the size of the light,) but many lights tend to focus a high amount over the center of the light (where it beams down from the source,) then the numbers drastically lower as the light spreads out inefficiently (which is why it’s important to understand the numbers for coverage as well, especially if a vendor is claiming high PPFD numbers (which may be accurate, but you need to understand the spread correctly.)

Generally the higher the PPFD number the more intense the light is. If the light intensity is too high (by delivering too many photons whether per second or over the spread of the day) the chlorophyll pigment in the leaves gets damaged by photo oxidation (light bleaching.) This is why seedlings and young plants don’t typically need as strong/intense of lights (you don’t feed an infant a t-bone steak, right?) but instead gradually increasing the power/intensity through the life cycle of the plant. Dimmers are becoming popular on many grow lights exactly for this reason (or controlled via box/board.) There are grow lights and add-on electronics that are able to literally simulate and artificial sunrise and sunset with dimmers. Many LED grow lights use lenses, reflectors, optical diffusers, etc, to help control the spread and the beam of the light. HID lighting uses reflectors (winged, parabola, vented hoods,) to help control the spread of light.

It's become generally accepted that typically more light hours provided to autoflowers provides better results, but plants can only take in a certain amount of usable light in a 24 hour period. That number is not constant and varies between cultivar to cultivar, and at a certain point CO2 supplementation (and environmental tweaking) needs to be provided to make use of the higher PAR/PPFD some of these lights even provide. Otherwise it’s likely just wasted electricity.

18/6 is usually recommended as a minimum because it's one of the most recorded/reported light cycles (next to 20/4 and 24/0) for autos that growers use with great success.

Personally I’ve seen very little evidence that increasing light from 18/6 to 20/4 or 24/0 for autos is going to provide noticeable substantial gains to the plant (though it may change the physical growing structure of the plant, 24 hours of light tends to produce more squat plants (plants seek for light in the dark) which in turn can effect nodal spacing. I wouldn’t go as far to say it’s still not beneficial in some cases, but in my opinion, the success of that depends on your technology and quality of your lights and will vary from plant to plant, from case to case, grower to grower, environment to environment, etc. If it were that evident, it would be far less of an argument every time someone asked about it lol.

Dessert for thought if you’re a year-round grower, 18 hours of light in a 90 day average grow cycle (assuming 4 grows per year) is 6,480 hours of electrical draw on your light. 24 hours on the same time line is 8,640 hours of electric draw. That’s literally an ENTIRE extra grow’s worth of electricity spent on what some might be considered negligible gains. If you run multiple lights, that’s some coffee money adding up there. Mileage will vary of course based on skill, environment, just nature being nature (she and Murphy’s Law have a lot in common, have to throw in that scapegoat disclosure.)

 

[Simplicio]

Well said @Waira

That's the reason why I switched from 24-0 to 20-4.
The plants were being over-stressed, and didn't look as healthy as they should've.

 

[pcgrower]

Have run 24/0 for some time now, I feel my girls finish quicker than they did and yeild 5-10% more

 

[The Iconoclast]

The more the light the more the bud, but without sleepy time she will be pissed off, it's not the way to the best much less the biggest harvest.