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Best light schedule during vegetation?

  • by RealEyesRealizeRealLies
  • Nov 13 2008 02:56 AM
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Posted 13 November 2008 - 02:56 AM

I'm still unsure of what is the best light schedule for the vegetation phase. (24/0, 18/6, 20/4?) I am on day ten of my grow and I am growing 3 plants with four CFLs (not sure what wattage). For the first couple days after they sprouted I had the lights on an 18/6 schedule then after that I switched to 24/0 because I heard that was better. I am debating whether I should switch it back or keep it the same because I recently heard bad things about 24/0 and good things about 18/6.
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  • Cannaseur

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Posted 13 November 2008 - 03:01 AM

24/0 will grow more veg but with 18/6 your plant will probably respond to the flower inducing photoperiod change. The results are very negligible and vary based on strain but if you like simplicity go with 24 hours if you want to save money on electricity use 18/6.

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  • groob4000
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Posted 13 November 2008 - 03:03 AM

as far as i know about what i have learned about plants is that they preform an act that can only happen while they are not performing photosynthesis, hence the lights being off. this is called respiration. also i would recommend most of all not to switch them back and fourth. keep them at one place til flowering

hope this helps:smoking::)

  • Proud Papa

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Posted 13 November 2008 - 03:55 AM

This debate comes up so often that it could probably have it's own message board. It is a debate that will rage for as long as people are growing marijuana. I have always used a 24/0 light cycle for veg and this is why.

This is a direct quote from Ed Rosenthal whom most of you know is a marijuana growing guru...

"Marijuana plantes photosynthesize as long as they receive light as well as water, air, nutrients and suitable temperature. Photosynthesis is the process in which plants use the energy from light (primarily in the blue and red spectrums) to combine carbon dioxide (CO2) from the air and water (H2O) to make sugar while releasing oxygen to the air.

Plants use sugars continuously to fuel metabolic processes (living) as well as for tissue building. The plant combines nitrogen (N) with the sugar to make amino acids, the building blocks of proteins. They are the substance of plant tissue. When the light is off, the plant's metabolic processes, respiration and growth, continue.

The plant can photosynthesize continuously so it produces the most energy and growth when the light is on, continuously. Continuous light does not stress the plant, which reacts somewhat mechanistically to it.

Plants under an 18-6 light-dark regimen are producing sugar only three quarters of the time. They are thus growing at only 75% of their potential. Leaving the light on continuously will result in bigger plants, faster, which leads to higher yields."

As for respiration. The main benefit of allowing the plant to respirate is to strengthen the root structure. If stability of your plants is an issue, then 18/6 may work better for you. However, if you want maximum yield (which I believe is the point) I would suggest 24/0 as the light cycle of choice.

Hope this helps.

  • Proud Papa

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Posted 13 November 2008 - 03:56 AM

24/0 will grow more veg but with 18/6 your plant will probably respond to the flower inducing photoperiod change.

I have never noticed any stress induced by switching from 24/0 to 12/12. Do you have some scientific data that supports this claim? If so, I would love to see it. I am always down with learning new things.


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