Amount of light?

[Delps8]

I think it was in an interview that he had with the Cornell where I captured some notes

[time passes]

Hmm, it might have been a Mr Growit video. In my defense, I was listening to the video while reading news stories!

Most of his comments were the same info I've heard from him in other places so these are the only notes that I took:

"
two stage adaptation to increased light 300 - 1200 in a few days
Short term and then long term adaptation

1000 or 1200 µmols is economic maximum
even at 1600 yield increases

light goes up 30% yield goes up 15%

"Don't have much margin for error" "all the other things ahve to be co-optimized"

CO2 - 1k ppm is optimal

must remember that water increases with light intensity

CMH is 30% blue
HPS 4% blue good spectrum

3% to 10% blue - 25% blue is too high, not optimal for photosynthesis

prune for disease and air"


What made me think of this was the 30% more light ===> 15% more yield. That sounds like a really rough metric but it's helpful even if it's just in the ballpark.

Something else of interest - from DeBacco.

He states that's from a "4' x 4' table". I assume that's a "drain to waste table."

View attachment 1487736

It would appear that 71 µmols is the light compensation point.

 

[Death The Cultivator]

Thanks for running the math. Granted that there's no "standard" grow site but, since you've been involved at the commercial level, would the extra 11 gm/ft2 be economically sound?

I think it would be a waste overall. You'll have a higher input for a ~15% increase compared to running the more economical model. An additional flower room would bring 4-6 harvest more a year whereas running each room at 30% more light requiring more water, HVAC, training, pruning, etc plus staff are going to drain that little increase in yield. I think running a SOG with shorter plants that can use all 1200umols, spend less time in veg, don't require pruning will capitalize on space and bring in a few extra harvest.

 

[Delps8]

Update

I'm at about 18" and 100% power.

37 days old.

Great looking plants! I don't see any sign of nute deficiencies but they look quite green to me. Could just be a color cast or a little rich on the N?

At 100% and 18" hang height, your light is generating an average PPFD of 760 µmols which is a DLI of 49 mols. Directly under the center of the light, it's 816 µmols or a DLI of ≈ 53. Check out the PPFD map for 12" hang height. At that height, you're getting really close to 900 µmols across much of the center of the tent. If the plants are happy with that, all well and good. If not, you might try leaving light at 12" but backing off on the % on the dimmer.

What about starting a grow journal? I realize the grow is well underway but "better late than never".

 

[Butrod]

It would appear that 71 µmols is the light compensation point.

If I may ask what's the source of that number?

 

[Butrod]

I think it would be a waste overall. You'll have a higher input for a ~15% increase compared to running the more economical model. An additional flower room would bring 4-6 harvest more a year whereas running each room at 30% more light requiring more water, HVAC, training, pruning, etc plus staff are going to drain that little increase in yield.

I don't see how you have more work by just ramping up lighting power in comparison to install another bloom room or tent.
The former is obviously more easy to pull off with way less work, space- & hardwarecosts associated.
Then there's also the question if that is even feasable in any situation.

To pick up on your previous example stated, in my situation a raw calculation would be:
1/3 pound = +900 bucks -45 bucks for electricity. Water, fert is really negligible in comparison, esp. when another tent would mean way more of these things really. The maximization of what I currently got represents less hardware costs in most aspects.

Another growtent would require space that isn't really there, require a full new setup plus increasingly more time. There's more plants then so the high-irradiance option is way less work and hardware costs. And no real approach to maximize what I already got here since even if I decide to enlarge my growarea would then also consider to pump as much light as possible to increase harvest.

So for me it's about to maximize what I already got and anything that leads to more harvest will pay heavily out as I do black market stuff. That's a way different story than official commercial big grow ops, although if I were to have to build a new facility from scratch, like the few that have an official state license, saving on space will mean nnn.nnn€ saved in buildcost, fees and else.
Everything is associated with a cost, can't just think of theoretical endless free expansion.

The most crucial point for me is if more light actually really translates into more harvest.
A few pages ago we were at the light-saturation point at 680umol/s PPFD which is grossly a 600 HPS in a 4x4. At that, I'd say YES of course, as experience showed the same clones run under double the light (300W LED 3x3) bucked up way faster, and much more dense/heavy. The HPS severely lacked light in the corners, with 15k lux there's not much sellable to be gained...

I think you are spot on with SOGs and these are also highly space-effective. The long veg-time with absurd tall plants kills so many calculations but that goes unnoticed due to "grams per watt" instead of "grams per killowatthour".

 

[Delps8]

If I may ask what's the source of that number?

Good question and, thinking through my reply, I believe my assertion is wrong. Further, either the formula is incorrect or there's more to the issue than the formula that DeBacco provides.

When I saw "Yield = 71.685 + 0.41 PPFD with an R2 of 0.88", I mistook the ≈ 72 to be the LCP because it's the intercept of the yield curve. That's a result of haste and confirmation bias. The confirmation bias aspect is because the 72 figure is in the ballpark of the LCP value here.

It appears that the formula is incorrect because, according to the formula, the 4' x 4' table would generate 72 gm of cannabis with a PPFD of 0. I find that unlikely.

Rethinking the issue, it seems that either there are constraints that have not been specified or perhaps it's a typo and the correct formula is "yield = -72 + 0.41 PPFD".

[time passes]

The paper that's cited is not available for download so I've written the lead author, asking for clarification. It's a long shot that I'll get a reply but, if I do, I'll update the thread.

 

[Delps8]

I don't see how you have more work by just ramping up lighting power in comparison to install another bloom room or tent.
The former is obviously more easy to pull off with way less work, space- & hardwarecosts associated.
Then there's also the question if that is even feasable in any situation.

To pick up on your previous example stated, in my situation a raw calculation would be:
1/3 pound = +900 bucks -45 bucks for electricity. Water, fert is really negligible in comparison, esp. when another tent would mean way more of these things really. The maximization of what I currently got represents less hardware costs in most aspects.

Another growtent would require space that isn't really there, require a full new setup plus increasingly more time. There's more plants then so the high-irradiance option is way less work and hardware costs. And no real approach to maximize what I already got here since even if I decide to enlarge my growarea would then also consider to pump as much light as possible to increase harvest.

So for me it's about to maximize what I already got and anything that leads to more harvest will pay heavily out as I do black market stuff. That's a way different story than official commercial big grow ops, although if I were to have to build a new facility from scratch, like the few that have an official state license, saving on space will mean nnn.nnn€ saved in buildcost, fees and else.
Everything is associated with a cost, can't just think of theoretical endless free expansion.

The most crucial point for me is if more light actually really translates into more harvest.
A few pages ago we were at the light-saturation point at 680umol/s PPFD which is grossly a 600 HPS in a 4x4. At that, I'd say YES of course, as experience showed the same clones run under double the light (300W LED 3x3) bucked up way faster, and much more dense/heavy. The HPS severely lacked light in the corners, with 15k lux there's not much sellable to be gained...

I think you are spot on with SOGs and these are also highly space-effective. The long veg-time with absurd tall plants kills so many calculations but that goes unnoticed due to "grams per watt" instead of "grams per killowatthour".

From the Abstract of the paper that Debacco cited:

"The purpose of this study was to analyze the relationship between light intensity, cannabis yields, and profitability. We also look for evidence that spectrum differences across broad-spectrum, horticulture lights and general-purpose LEDs impact the relationship between yield and light intensity. Finally, we discuss the financial return of increasing light intensity in order to increase yields. We find that yields increase linearly with light intensity up to at least 1500 μmols/m2·s, which is at least twice the intensity that is most commonly used by cannabis growers. That relationship did not appear to be influenced by spectrum quality differences across the lamps included in the study. Finally, for all the intensity ranges that we considered, the value of the gain in yields from increasing light intensity far exceeded the cost of using more electricity."

I did read a paper early this year that studied a commercial grow in Ontario and they came to a similar conclusion - the crop is so valuable that the increased revenue far exceeded the cost of production. There are, of course, variable costs other than electricity. Given that the purpose of a cannabis farm is to grow and process cannabis, unless the increase in yield is such that it requires additional expenditures in fixed costs, it's difficult to see how simply processing more cannabis would not be profitable. If processes and equipment were efficient and scalable, increased yield should lead to a decrease in production costs per unit since you're spreading the fixed costs over more units.

 

[Butrod]

From the Abstract of the paper that Debacco cited:

"The purpose of this study was to analyze the relationship between light intensity, cannabis yields, and profitability. We also look for evidence that spectrum differences across broad-spectrum, horticulture lights and general-purpose LEDs impact the relationship between yield and light intensity. Finally, we discuss the financial return of increasing light intensity in order to increase yields. We find that yields increase linearly with light intensity up to at least 1500 μmols/m2·s, which is at least twice the intensity that is most commonly used by cannabis growers. That relationship did not appear to be influenced by spectrum quality differences across the lamps included in the study. Finally, for all the intensity ranges that we considered, the value of the gain in yields from increasing light intensity far exceeded the cost of using more electricity."

I did read a paper early this year that studied a commercial grow in Ontario and they came to a similar conclusion - the crop is so valuable that the increased revenue far exceeded the cost of production. There are, of course, variable costs other than electricity. Given that the purpose of a cannabis farm is to grow and process cannabis, unless the increase in yield is such that it requires additional expenditures in fixed costs, it's difficult to see how simply processing more cannabis would not be profitable. If processes and equipment were efficient and scalable, increased yield should lead to a decrease in production costs per unit since you're spreading the fixed costs over more units.

Here's the full study - they did use CO2, which is like 20 bucks for +30% more harvest and more resilient plants.

It comes to the conclusion that more light translates to a LINEAR increase in harvest weight. Unlike the often-cited diagrams about photosynthesisrates that show a flattening of the curve.
It's simply wrong to equate photosynthesisrates with harvest mass, and that has physiological reasons, some of which are discussed in my cited studies a few pages back.

One important factor pointed out is that indoors light dominishes with the distance so only the tops receive the full PPFD while the middle parts that still manage to get direct light only gets a fraction of it. Even way less if shaded. So this is how even too high irradiance can be helpful.
And the other study also described the net gain via a linear metric although looking at the diagrams it's not as clear-cut as they wrote it imo.

 

[Delps8]

Here's the full study - they did use CO2, which is like 20 bucks for +30% more harvest and more resilient plants.

It comes to the conclusion that more light translates to a LINEAR increase in harvest weight. Unlike the often-cited diagrams about photosynthesisrates that show a flattening of the curve.
It's simply wrong to equate photosynthesisrates with harvest mass, and that has physiological reasons, some of which are discussed in my cited studies a few pages back.

One important factor pointed out is that indoors light dominishes with the distance so only the tops receive the full PPFD while the middle parts that still manage to get direct light only gets a fraction of it. Even way less if shaded. So this is how even too high irradiance can be helpful.
And the other study also described the net gain via a linear metric although looking at the diagrams it's not as clear-cut as they wrote it imo.

Thank you for posting that paper. It sounds like a good read. And I hope it will…shed some light on the basis for the 71.x value in the yield curve.

"It's simply wrong to equate photosynthesisrates with harvest mass, and that has physiological reasons, some of which are discussed in my cited studies a few pages back."
Agreed.

Re. light only on the canopy. Agreed. Having light below the level of the canopy sounds intriguing.

 

[Talonxracer]

Light only on the canopy. Agreed. Having light below the level of the canopy sounds intriguing.

Believe me when I say that side lighting works! It's only issue is when tents are full, but if you have the room it really helps the lower buds bulk up. At the same time you can usually turn down the overhead light so as to not light stress upper colas.