Take a look at this.

What does this mean when growing flowering plants? What are the advantages of a 24/0 or 18/6 light cycle when it is more natural for it to be closer to 12/12 or 16/8?

[Crusader Rabbit]

The goal isn't to be natural. The goal is to grow great bud. Manipulating the light cycle allows you to manipulate the plant's flowering to further that goal.

[habeeb]

well I don't know who does 24, but there hurting there electric bill

I run all my plants on 16 on, and flowering 11 on

for the link I cannot say as I don't click outside links

[pezmasterelite]

Plants photo-transpiration processes has reverse roles which are beneficial to the plant when it is not photosynthesizing. I talked to a botanist when I was in school about this and she said it would not be very wise to deny plants this period of darkness, even if for a short amount of time.

habeeb, what types of strains do you run on those photoperiods? Was there a reason you went with 16 hours compared to 17 or 18?

thanks

pez

[delta9nxs]

Vegetative light schedules

24/0-20/4-18/6, and now 8/4/8/4.

For some time I have been using a vegetative light schedule of 8 hours on, 4 hours off, 8 hours on, and 4 hours off. Or 16 hours of light per day.

My plants are reaching the same size in the same time frame with this schedule as they as they did with the 20/4 schedule I was using immediately prior to the change to 8/4/8/4.

Everyone has seen the numerous threads over the years about which vegetative light schedule is best. They always degenerate into arguments that are never resolved. One person swearing by 24/0 and another saying 18/6 is the best.

The arguments for or against any regime are flawed without considering the amount of light actually received by the plant. And, as we shall see, all the arguments are futile and rendered obsolete simply by using a tool to measure your light.

If you are using powerful lighting at the right distance you need less time to achieve the size plant you desire than someone using weak lighting.

What is the right distance? Dr El Sohly at the University of Mississippi has determined that the maximum rate of photosynthesis for cannabis occurs at 1500 umols of photon bombardment, which is an instantaneous measurement of flow. The only way to determine this is with a quantum sensor. This distance to produce 1500 umols will be different for every type of lighting or bulb.

I can do the 8/4/8/4 routine because I use a 1k hps hortilux during the vegetative period and run my light at 14” to the closest part of the plant, which is the distance producing a 1500 umol flow with my light.

Someone using fluorescents or low wattage mh or hps bulbs in the vegetative stage will have to give the plant more time to reach the same goal. If the lights you use are very weak you may not be able to reach the same growth I get even if you go 8 more hours and give the plant 24/0.

All of this is because of the daily light integral. The total amount of accumulated light a plant gets in a 24 hour or diurnal cycle. The maximum daily light integral for cannabis is not currently known but we know that it is a “high light” plant. We know that the most sunlit places on earth rarely get more than about 60 moles/day and that plants in most greenhouses get no more than about 30 moles/day.

In order to determine the correct vegetative light exposure for your plant with your light you need a quantum meter.

Using one I was able to determine that, at 14”, with my light, I was able to deliver approximately 32 moles in each 8 hour period. Or 64 moles/day. A huge amount of light that , if given in one continuous period, would probably be more than the plant could process.

But I believe that the rest or dark periods allow the plant to process enough photosynthate in between light periods to be able to process that light.


There is really nothing to argue about. Just to
measure.

d9

[Crusader Rabbit]

Originally Posted by delta9nxs

But I believe that the rest or dark periods allow the plant to process enough photosynthate in between light periods to be able to process that light.


There is really nothing to argue about. Just to
measure.

d9

What an informative post.

We can argue about what we believe plants' dark requirements might be. But that is something else that will only be resolved by measurements. Might be a good side by side experiment.

[CannabisFox]

And what about manipulating the day lenght to more then 24h ?

like 18/12 for flowerin ?

[LittleAmsterdam]

Ed Rossenthal talks about increasing the day length during flowering after it's been initiated.... I'm curious who has ever tried this?

I'm in hydro and it's hard to move plants around for testing purposes. Maybe ones of these days I'll have enough extra $$ to run these type of experiments.

[Phaeton]

Using a 6 day week of 16/12 bud cycles with was written up by somebody a while back with positive results. I also have read the Daily Light Integral thread. There are also threads on 24/0 veg cycles with positive results.
I compare these techniques as compensating for inadequate lighting.
24/0 helps if the plants are don't get enough light enough in a shorter time, no sleep beats starving every time.
A 16/12 bud cycle helps if the light is too weak for a full meal in 12, snacking continuous all day plus midnight snacks after bedtime will keep you big same as a big meals three times a day, just not as healthy.

That 8/4/8/4 does sound like an excellent method to rapidly veg trees.

[DJOGBK]

Originally Posted by delta9nxs

Vegetative light schedules

24/0-20/4-18/6, and now 8/4/8/4.

For some time I have been using a vegetative light schedule of 8 hours on, 4 hours off, 8 hours on, and 4 hours off. Or 16 hours of light per day.

My plants are reaching the same size in the same time frame with this schedule as they as they did with the 20/4 schedule I was using immediately prior to the change to 8/4/8/4.

Everyone has seen the numerous threads over the years about which vegetative light schedule is best. They always degenerate into arguments that are never resolved. One person swearing by 24/0 and another saying 18/6 is the best.

The arguments for or against any regime are flawed without considering the amount of light actually received by the plant. And, as we shall see, all the arguments are futile and rendered obsolete simply by using a tool to measure your light.

If you are using powerful lighting at the right distance you need less time to achieve the size plant you desire than someone using weak lighting.

What is the right distance? Dr El Sohly at the University of Mississippi has determined that the maximum rate of photosynthesis for cannabis occurs at 1500 umols of photon bombardment, which is an instantaneous measurement of flow. The only way to determine this is with a quantum sensor. This distance to produce 1500 umols will be different for every type of lighting or bulb.

I can do the 8/4/8/4 routine because I use a 1k hps hortilux during the vegetative period and run my light at 14” to the closest part of the plant, which is the distance producing a 1500 umol flow with my light.

Someone using fluorescents or low wattage mh or hps bulbs in the vegetative stage will have to give the plant more time to reach the same goal. If the lights you use are very weak you may not be able to reach the same growth I get even if you go 8 more hours and give the plant 24/0.

All of this is because of the daily light integral. The total amount of accumulated light a plant gets in a 24 hour or diurnal cycle. The maximum daily light integral for cannabis is not currently known but we know that it is a “high light” plant. We know that the most sunlit places on earth rarely get more than about 60 moles/day and that plants in most greenhouses get no more than about 30 moles/day.

In order to determine the correct vegetative light exposure for your plant with your light you need a quantum meter.

Using one I was able to determine that, at 14”, with my light, I was able to deliver approximately 32 moles in each 8 hour period. Or 64 moles/day. A huge amount of light that , if given in one continuous period, would probably be more than the plant could process.

But I believe that the rest or dark periods allow the plant to process enough photosynthate in between light periods to be able to process that light.


There is really nothing to argue about. Just to
measure.

d9

lol I just asked in another thread if anyone has tried 6/6/6/6 or 7/5/7/5 or somethine alone those lines now I read you do 8/4/8/4 I knew someone must of tried it. have you experimented with other light schedules other then 8/4/8/4? do you find that the best?