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Effects of different photoperiods on flowering.

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    #16
    7/12 cycle

    Hi Blckbrd.

    I'm interested in learning more about this 7/12 flowering cycle you use. You can contact me directly by message or email you want. I'm thinking about doing it, but I have also read that 12 hours of light and 6 hour of dark will work (See uphill post at http://forum.grasscity.com/advanced-...rk-time-2.html) I get it about the 20-25% increase in production. I'd like to know how many watts/ m2, and the strains and nutrients you are using.

    Thanks for posting your interesting experience.

    @@@@@@@@@@@@@@@@@@@@@@@@

    Originally posted by Blckbrd View Post
    I flower using 7 on / 12 off. I veg at 24 hrs-on for up to a month to get the desired size, then use a cycle timer for the 7 / 12. Yeild has always been fantastic using 1000w. I suppose the theory is that they might get a little bigger (?) with a few more hours of sun a "day"/dark period.

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      #17
      gosh if 7 on 12 off works thatd save a bundle of money in electricity!

      Comment


        #18
        Originally posted by JewBilly View Post
        Hi Blckbrd.

        I'm interested in learning more about this 7/12 flowering cycle you use. You can contact me directly by message or email you want. I'm thinking about doing it, but I have also read that 12 hours of light and 6 hour of dark will work (See uphill post at http://forum.grasscity.com/advanced-...rk-time-2.html) I get it about the 20-25% increase in production. I'd like to know how many watts/ m2, and the strains and nutrients you are using.

        Thanks for posting your interesting experience.

        @@@@@@@@@@@@@@@@@@@@@@@@
        Sorry for the delay .. just found this thread again. 12-on and 7-off seems like another way to speed up the 12/12 cycle. Might be useful for those sativa/haze strains. I do a 24 hr on vegetative & have never tried shortening the night cycle. I'd be inclined to do something less than 12 on, however, to ensure triggering the plant's flowering.

        I use GH flora series under 1000 watts/4x4'. Always very happy, barring the invasion of some effing virus that I am now battling.

        Comment


          #19
          Originally posted by Charybdis View Post
          If you have a strain that flowers readily - say under 16 hours of light - would you be better off to switch to 12/12, or if it'll flower at 16 should you go with 16/8? It seems to me that if it'll flower with more light, you'd get more growth at 16 than 12. I know some growers run pure sats at 11/13 or even 10/14 instead of 12/12, but I think that's usually just to get them to actually flower.

          Also, I don't remember where I read it but I remember hearing about a fairly new technique where you can run 12/6 - with a dark period half as long - and still get the same yield in reduced time. Is anyone here familiar with that? I couldn't find any threads on it.

          Thanks.


          Cannabis is a 'long night' plant, so it needs 10-12 hours of darkness to flower, the hours of light doesn't effect flowering, that's the job of darkness. That said, you could change the diurnal hours (length of one day) from 24 hours to 28 hours, that is what I do. I use 16/12 for flowering. For pre-flower I use 8 on/12 off; that limits stretching and helps keep internodes close, it also reduces the pre-flower time from say 14 days to 10-12 days. 8 hours is about as little daylength as is wise.

          For veg I use 16/8. It's best to not exceed 16-17 hours of light a day, 18 hours can be too much in terms of reducing Pn (rate of photosynthesis), carbon assimilation and partition, etc. Running lights at 24/0 will make the Pn drop drastically after the first two-three days or so.

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            #20
            The info about 6 hours of darkness has to do with far-red lighting and Pf/Pfr (ie. phytochrome). It's not proven for cannabis and IMO is not worth pursuing at all, 12-14 hours of darkness per night is good.

            Comment


              #21
              Originally posted by LJB View Post
              I know one grower / scientist with a working theory about 32 hour photoperiod.... That is 18 on, 14 off during bloom. He swears by it.

              I have nothing else to add.

              I changed from that 32 hour diurnal to a 28 diurnal last grow. Now I am using 16/12; not 18/14. I have done a lot of research into this (more lately) and it seems 18 hours is less ideal than 16 hours. I reduced the nightlegth from 14 hours to 12 hours to shorten the diurnal considering I reduced the daylength by 2 hours.

              All the best.

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                #22
                I've heard of switching to 14 on 10 off during weeks 6-7 of flowering.
                Saw it in a grow video somewhere.

                Also, there is the 23.5/12 method making a week 5 days. Never tried that one...
                My Sigs got annoying. BOG Love.

                Comment


                  #23
                  Most of what people "hear" and are "told" is BS. Look at this thread for example, many people are talking about < 10 hours of nightlength to flower! There is no reason to use a 24 hour diurnal, thus if we increase the diurnal we can offer 14/12, 16/12, 16/16, whatever.

                  HTH (what I wrote above should be what people trust, not the other info in this thread or elsewhere...I can offer full references backing up all my claims)

                  Comment


                    #24
                    Originally posted by secondtry View Post
                    I changed from that 32 hour diurnal to a 28 diurnal last grow. Now I am using 16/12; not 18/14. I have done a lot of research into this
                    Why is 16/12 superior to 12/12? Not doubting, just don't know what the advantage is.
                    Are we talking the same number of calendar days to finish for each? Or same amount of "on" time?
                    What type of timer is used to do this? I have interval timers that do minutes, so assume it's the same principal, only w/ hrs?
                    Thanks ----------- CB
                    "You cannot manage what you cannot measure.”
                    Bill Hewlett (Cofounder Hewlett Packard)

                    Comment


                      #25
                      Hello,

                      The main benefits are greater net photosynthesis, carbon assimilation, carbohydrate partitioning, etc, and in cannabis that seems to equate to increased growth and yield. Below I posted my references on the science. I am not sure what you mean by "on" time. Each day is 28 hours, not 24; so a week is 196 hours, not 168 hours. We can change the hours of one full day (daylength plus nightlength) because cannabis isn't dependent upon circadian rhythm, it is dependent upon hours of darkness for flowering and for not-flowering.

                      You could order special timers do to this digitally which is a real bonus, maybe $50-100. But you could also use a regular timer because we are only changing the daylength, not the nightlength, thus once the daylength pass the 4 hour mark you can turn the dial back 4 hours, but that means you need to be there each daylength.


                      Here is some references from my Zotero:
                      "16 hr Daylength: Diurnal Pn, circadian rhythms and carbon assimilation"
                      1. “SUPPLEMENTAL LIGHTING OF GREENHOUSE VEGETABLES: LIMITATIONS AND PROBLEMS RELATED TO LONG PHOTOPERIODS,”
                      http://www.actahort.org/members/show...knrarnr=481_54

                      2. “REGULATION OF ASSIMILATE PARTITIONING BY DAYLENGTH AND SPECTRAL QUALITY,”
                      http://ncr101.montana.edu/Light1994C...itz%20text.htm

                      3. “LIGHT PERIOD REGULATION OF CARBOHYDRATE PARTITIONING,”
                      http://ncr101.montana.edu/Light1994C...nes%20text.htm

                      4. “Independent Circadian Regulation of Assimilation and Stomatal Conductance in the ztl-1 Mutant of Arabidopsis,”
                      http://www.jstor.org/pss/1514476

                      5. “Factors affecting the rate of photosynthesis,”
                      http://web.archive.org/web/200303060.../2385/rate.htm

                      6. “Environmental effects on circadian rhythms in photosynthesis and stomatal opening,”
                      http://www.springerlink.com/content/m275226261246h24/

                      7. “COORDINATING PHOTOSYNTHETIC ACTIVITY: CIRCADIAN RHYTHMS,”
                      http://www.tiem.utk.edu/bioed/webmod...ianrhythm.html

                      8. “Circadian Rhythms in Photosynthesis : Oscillations in Carbon Assimilation and Stomatal Conductance under Constant Conditions,”
                      http://www.plantphysiol.org/cgi/cont...tract/96/3/831

                      9. “859.pdf,”
                      http://www.plantphysiol.org/cgi/reprint/102/3/859.pdf

                      Comment


                        #26
                        Oh yea,

                        I use an hour or darkness mid-daylength to give the plant a rest and lower leaf temp, which means I really give the plants 15 hours of light in a 16 hour daylength. For example you can put an hour of darkness starting at hour 4.5 of daylength so when you spin the timer back it basically hits half way through the day. Or you a digital timer.

                        Comment


                          #27
                          Originally posted by secondtry View Post
                          Hello,

                          The main benefits are greater net photosynthesis, carbon assimilation, carbohydrate partitioning, etc, and in cannabis that seems to equate to increased growth and yield. Below I posted my references on the science. I am not sure what you mean by "on" time. Each day is 28 hours, not 24; so a week is 196 hours, not 168 hours. We can change the hours of one full day (daylength plus nightlength) because cannabis isn't dependent upon circadian rhythm, it is dependent upon hours of darkness for flowering
                          Sorry I wasn't clear. By "on" time I meant day (or lights ON).
                          Maybe an example would help. We know we have to have the 12 dark. Now we have 3 choices --- I know we have more, but bear w/ me ---- 8 or 12 or 16 hrs of light. W/ 12 as our base, would the lower input expense compensate for what the smaller 8hr schedule would yield? And conversely, would the extra 16 expense be justified by its increase? Really only increasing by 7% the total "on" time, so gains wouldn't have to be that great to justify. Be interesting to try w/ the right timer ----- can't see my inconsistent ass adjusting it everyday.
                          Thanks for all the references. Great to have them in one place. I'll try to wade thru them soon.
                          CB
                          "You cannot manage what you cannot measure.”
                          Bill Hewlett (Cofounder Hewlett Packard)

                          Comment


                            #28
                            Originally posted by LJB View Post
                            Who rated my posted as not being helpful and didn't bother to respond it?

                            The grower asked about using more than 12 hours of light during the bloom cycle.

                            I explained why people attempt do this which also explains why it might not work and also mentioned someone else's working theory.

                            What is anti-helpful about this? The title of the thread is " Effects of different photoperiods on flowering"...

                            edit: I see it was Maj.PotHead.

                            So what's the problem with the information that was posted? Explain your actions for the rest of us.
                            i thought your post was informative man....
                            Best Link: http://www.angelfire.com/cantina/fourtwenty/yor/yor.htm

                            **All correspondence from Matanuskan Flo is purely hypothetical & typed under extreme intoxification.**

                            Comment


                              #29
                              Originally posted by Carboy View Post
                              Sorry I wasn't clear. By "on" time I meant day (or lights ON).
                              Maybe an example would help. We know we have to have the 12 dark. Now we have 3 choices --- I know we have more, but bear w/ me ---- 8 or 12 or 16 hrs of light. W/ 12 as our base, would the lower input expense compensate for what the smaller 8hr schedule would yield? And conversely, would the extra 16 expense be justified by its increase? Really only increasing by 7% the total "on" time, so gains wouldn't have to be that great to justify. Be interesting to try w/ the right timer ----- can't see my inconsistent ass adjusting it everyday.
                              Thanks for all the references. Great to have them in one place. I'll try to wade thru them soon.
                              CB
                              I tend to not care about cost of running lamps, I can't understand why people want to skimp on electricity to grow plants, and that seems to be a common thought around here. I try to grow the best plants, not just grow plants with the lest energy input.

                              HTH

                              Comment


                                #30
                                I found this on another site. This is what I was talking about.


                                The only photoperiod manipulation from years of experiments that offered discernible improvements was the following photoperiod adjustment made for 1 or 2 calendar weeks at the point of maximum flowering rate: Daylength of 21 hours, 36 minutes with a dark period of 12 hours. To accomplish this, you need a 7 day, 24 hour digital timer. During a 7 day calendar week on Earth, the "sun" only cycles 5 times. This permits easily switching back to the regular 12/12 at your discretion. You may want to only alter during peak flower production to stimulate the plant's metabolism. Using this photoperiod throughout the flowering cycle will cause this:

                                A variety that takes 49 days of 12/12 to mature, won't see 49 - 12 hour dark periods under 21:36/12 until almost 10 calendar weeks have passed.

                                The total increase in light energy is almost 80%, which will produce larger yields, if all of your other enviromental conditions are kept optimal.

                                The total increase in flowering period is only 40%, half the potential room for improvement. This means you don't have to be perfect to win out.

                                Selective application of the 21:36/12 photperiod for only 1 or 2 weeks extends the wait only 2 to 4 Earth days, which makes up the missing 2 complete day and night cycles each week on Planet Ito. This permits the additional light energy to be provided without purchasing additional equipment or overloading existing circuits, which maximizes the existing system's capabilities. The main advantage is that matched with co2 and optimal nutrition, the plants metabolism will increase dramatically. I have only successfully tested this photoperiod for two weeks. The potential for a net increase of 40% over the entire cycle (80% increase in light energy vs. 40% longer wait) is worthwhile. Don't be afraid!

                                Day 1 - Sunday, 6:00am til Monday, 3:36am
                                Day 2 - Monday, 3:36pm til Tuesday, 1:12pm
                                Day 3 - Wednesday, 1:12am til Wednesday, 10:48pm
                                Day 4 - Thursday, 10:48am til Friday 8:24am
                                Day 5 - Friday, 8:24pm til Saturday 6:00pm
                                My Sigs got annoying. BOG Love.

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