12/12 vs 18/6 ... DLI vs Yield

[Simplicio]

Sure, but 400k lux is around 9000 ppfd and the maximum amount of ppfd you can give to cannabis is ~1500.

The 400 kLux was an outrageous amount of light, my attempt at "proof by absurdity."
Too intense light hurts plants.
I suspect without proof that plants would prefer 24,000 Lux for 18 hours over 36,000 Lux for 12 hours, even though they have the same DLI.


My suspicions arise because I sometimes light stress my plants with less light than is usually recommended.

 

[KodakB]

The 400 kLux was an outrageous amount of light, my attempt at "proof by absurdity."
Too intense light hurts plants.
I suspect without proof that plants would prefer 24,000 Lux for 18 hours over 36,000 Lux for 12 hours, even though they have the same DLI.


My suspicions arise because I sometimes light stress my plants with less light than is usually recommended.

Indeed. In my current grow, i was trying to push it to 60 DLI and one my autos started showing symptoms of light stress that immediately stopped after i increased light distance.

The problem with high DLI is that you need all other parameters to be equality high. CO2, oxygen, water, airflow and nutrients.

 

[OregonBlackBear]

You dont need a better light. Closer light distance increases DLI. I'm done arguing with you.

Moving your light closer/getting a better light have the same effect in your example. Once your plants are receiving their max light, duration of exposure is all that's left. By setting your light to 12/12 you are limiting your harvest when you could be running the light for 18 hours a day. Repeated tests on multiple forums have shown again and again that this is the case.

You recently learned that your plants will only accept a certain intensity of light before they turn away from it and start reacting negatively. Push it further and they will absolutely be damaged. I have had plants burned from light intensity. Have you run your lights as close to your plants as you can for both 12/12 and 18/6 and seen the results? I promise there will be a much better harvest from the 18/6.

In your original post you asked if using better light/more intensity a 12/12 could yeild the same as 18/6 with autos, and the answer is yes... but why? I still don't see why you would limit your grow, you have not explained that in any way.

I'm not trying to insult you when I say you're a new grower and need to put in more time with the plants to get to know them better. While you have researched a lot, you don't have the hands on knowledge to differentiate between what is good info and what is not. For example, ten days ago:

The high humidity might be causing the calcium lockout. Try lower the RH% and watch for recover.

That's just not true in any way. RH does not lockout calcium or anything else for that matter. I wouldn't continue to source information from wherever you learned that.

I wish you luck in your future grows and hope you get the experience you need.

 

[elcoloan]

...


That's just not true in any way. RH does not lockout calcium or anything else for that matter. ...

....

Actually, I have read -and might have seen in a run of mine - that low RH might cause Ca def sympotoms, but when i read it i think it was in rlation to another plant, not cannabis... But a wise AFN member once said... "If the stomata of the plant are closed to preserve moisture the plant stops respiring which means it cannot carry any calcium into a rapidly growing plant. This mimics a deficiency...", which could happen in low RH conditions.


Oh, and in regards to the threads topic... I think penetration could be an issue in the question you're posing @KodakB . Let me come down from the high I'm in right now and I try to explain why. I like the tpic BTW, got my self a par meter and all.

 

[KodakB]

I was under the impression that both very low RH or very high RH could make the stomata close and create a calcium deficiency. I regret making that comment. But still i find it odd that my unrelated comment history is being brought up.

 

[Mañ'O'Green]

I was under the impression that both very low RH or very high RH could make the stomata close and create a calcium deficiency. I regret making that comment. But still i find it odd that my unrelated comment history is being brought up.

You are correct and quoting me. I am guilty of not fully explaining the science behind the closing of the stoma. With high heat and low humidity the leaves actually close the stoma to prevent water loss and without transpiration deficiencies can and do occur in the plant. The High humidity has the same end effect but the the mode of activity is different. When the relative humidity gets too high the plant cannot pump the water up through the plant because of the osmotic pressure exerted by the heavy wet air against the leaves. The pressure is too high. It is complicated. The end result is that transpiration stops and so does the movement of the elements the water carries. It is much simpler to state that the stoma close. Bro science is easier to grasp.

My shortcut I apologize. Your right about DLI in here also to a point. Some yield may be lost if you don't have lights that can put out the higher DLI in a shorter period. Pretty sure that stems from Bruce Bugbee's work.

 

[KodakB]

@Man ty so much for the input.

Yes! I think i had actually experienced this myself in my first grow when i got hit by a heat wave and 16% RH. The plants stopped drinking all of the sudden and developed a calcium deficiency very rapidly. In my search to figure out what happend i had read about this stomata thing.


About the DLI, at the end of the day, im still keeping 18/6 because i cant afford the risk of lower yields... But i think this is a interesting discussion given the recent studies of Dr. Bruce Bugbee on Cannabis sativa L. which i think can be applied to autoflowers.

 

[KodakB]

I found this interview really interesting also. Dr. Bruce Bugbee debunks many myths on grow light and spectrums.

 

[King_of_cringe]

I get your point completely, I just think you're wrong. You're not talking about running different light cycles for the same yeild, you're simply saying a high quality light run 12/12 will outperform a mid to low quality light run 18/6. What I am saying is yeah no duh.

If you run your autos 12/12 you are going to get a reduced harvest, period. If it is advantageous to run your lights 12/12, then grow photos.

There's nothing new or special about that revelation, and I honestly am not concerned with what doctor youtube has to say about plants. Get a few grows under your belt and get to understand autos better, then revisit this.

You clearly don't understand DLI or the point he's trying to make. It's like trying to talk to a brick wall.

 

[nomadJ]

My autos do really well outside with far less than 18 hours of light. Some only get 8 hours of direct light but as we know sunlight if far better than other forms.