Max PPF/PPFD with and without Co2

[Megalomando]

Good question. Under traditional lighting heat is always a concern. With LED lighting, they run so cool, heat isn't much of a factor. It's easy to get too much light with COBs and that is much more concerning to me, especially with early/mid Veg. I'd like to know what is the most that is good.

 

[SPLFreak808]

Depends on where the reading was taken. Higher elevations may have less CO2 than lower ones, to what degree I do not know.

I do know that the average C02 PPM level for our atmosphere is pegged around ~400. There is a research station in the far north that has been measuring for a while (decades) and it has been steadily increasing, albeit at a slow rate.

Go into a city and things significantly change. Even time of day.

I know the post is a bit old but incase you would like the answer, that measurement was taken a mile away from an active volcano lmao.. Yes in a low pollutant state (hawaii) at high elevation (10,000+ft) but still, a fucking active volcano that inches closer and closer every day lol.

 

[Rahz]

I'm not sure what the PAR reading should be for Veg under 24/0 or 18/6, any suggestions?

You could easily go as low as 200-500 average. 400-500 produces fairly rapid growth IMO. 300 produces reasonable growth for rooted plants. 100 is good for clones, even less will get the job done.

Readings outside can be as high as 2500 in the Summer. The most efficient way to use a particular light is to get the grid average as high as possible and let the PPFD in the center be whatever it is. 1500 is probably close to max usefulness without CO2, but we don't generally want to design/use 1500 PPFD because it's also the least efficient way to go about it. There could be arguments for the sweet spot in flower being 650, 800, 1000, 1250 whatever but there's an electrical budget to consider and a 4x8 at 650 would do better than a 4x4 at 1300. Same electricity, more product. It just depends on what the goal is and the resources available. I would say the sweet spot for veg would be around 400 but again it depends on what the goal is and the time frames involved. If it would be useful to knock a week off a 4 week veg time then bumping the PPFD to 700 would do it, application specific like a full cycle scrog for instance. 300-400 is probably better for a dedicated veg area.

 

[Megalomando]

Rahz, thank you, I appreciate that.

 

[pirg420]

Not controversial.

This paper shows that with any canopy temp (20-40C) net photosynthesis increases upto a ppfd of 1500 umol/m2/s. That is without CO2.

Overall highest net photosynthesis occurs at 30C and 1500 umol/m2/s ppfd.

30C sounds like a mite factory.

 

[Hybridway]

id put quality above yield but that was prob a given in hybridland...

Yeah, that's a given. What good is max yields If nogo.
Genetics these days are sick.

 

[wietefras]

i always wonder if that chart specs leaf temp or ambient (prob ambient, and if so, what kind of light and leaf temp rise does it assume)

who knows the OG source article?

It's called "Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions" by Chandra et al.

They test leaves in a growth chamber. With the air in the chamber kept at the desired temperature and CO2 level.

 

[ttystikk]

I know the post is a bit old but incase you would like the answer, that measurement was taken a mile away from an active volcano lmao.. Yes in a low pollutant state (hawaii) at high elevation (10,000+ft) but still, a fucking active volcano that inches closer and closer every day lol.
View attachment 4015609

Having read into the work that station does, they're quite well aware of the fact that they reside on an active volcano. They also understand that most of the time, the prevailing winds carry volcanic gases away from the measuring equipment- and when it blows towards them, they recognize the situation and discard those readings.

They're scientists, they're not stupid, lol

FYI

 

[ttystikk]

30C sounds like a mite factory.

Only if it's too dry. VPD suggests that optimal conditions at that temperature would be around 80% RH. Not so mite friendly! Further, I've anecdotally noted that spidermite predators do very well indeed under just such conditions as these. This would certainly tilt the balance of power in favor of the predators and therefore the grower.

Read down the left to find your target temperature, then across to the green to find the RH corresponding to optimal VPD. 'Keep it in the green'.

 

[ttystikk]

Yeah, that's a given. What good is max yields If nogo.
Genetics these days are sick.

There is a persistent view that the goals of maximum yield and maximum quality are diametrically opposed to one another beyond a certain point, that what's best for one ends up degrading the other.

I have disagreed with this line of thinking since I first heard it but it is important to keep in mind.

Generally speaking, if a plant of mine has done particularly well in terms of yield, it's also been a high quality smoke.

I'm curious as to the thoughts of others on this subject.

 

[ttystikk]

From my most recent harvest of 3 different strains my heaviest yielder was also the most potent I have grown to date. I don't know if it's the heaviest yielder I've had but I know it very well could be. I've only just recently selected the pheno I plan to keep growing so time will tell what kind of yield I can really get out of her.

Your experience reflects my own suspicion that growing a really healthy plant leads to both great yield and great quality.

So far, equipment changes that vendor performance also benefit quality. For example, I think the single most underrated advantage to upgrading to LED from HID lighting (of any type) is the improvement in the quality of the product.

I've had people spontaneously comment on the difference from across the room.

 

[SPLFreak808]

Having read into the work that station does, they're quite well aware of the fact that they reside on an active volcano. They also understand that most of the time, the prevailing winds carry volcanic gases away from the measuring equipment- and when it blows towards them, they recognize the situation and discard those readings.

They're scientists, they're not stupid, lol

FYI

Fair point, actually stupid assumption from me.

I looked into it more, yes they don't pull data off the sensor during directional gasses/high wind.

It's also consistent with other labs around the world.

Now that i think of it,the middle of the pacific ocean might be a good place to read air quality when the islands don't trade heavy winds.

 

[waveman]

You could easily go as low as 200-500 average. 400-500 produces fairly rapid growth IMO. 300 produces reasonable growth for rooted plants. 100 is good for clones, even less will get the job done.

Readings outside can be as high as 2500 in the Summer. The most efficient way to use a particular light is to get the grid average as high as possible and let the PPFD in the center be whatever it is. 1500 is probably close to max usefulness without CO2, but we don't generally want to design/use 1500 PPFD because it's also the least efficient way to go about it. There could be arguments for the sweet spot in flower being 650, 800, 1000, 1250 whatever but there's an electrical budget to consider and a 4x8 at 650 would do better than a 4x4 at 1300. Same electricity, more product. It just depends on what the goal is and the resources available. I would say the sweet spot for veg would be around 400 but again it depends on what the goal is and the time frames involved. If it would be useful to knock a week off a 4 week veg time then bumping the PPFD to 700 would do it, application specific like a full cycle scrog for instance. 300-400 is probably better for a dedicated veg area.

Rahz, It seems you know what you are talking about. What PPFD would COB's running at 37Watts spaced 1 COB/sqft produce? At this level of PPFD will charging the room with CO2 be benificial vs the cost of generating it?

 

[indooryhydro]

@waveman - PPFD is dependent on the optics and distance from the light source. In other words, if you focused the COB beam angle very tightly (e.g. 15 degrees) and placed your plants very close to the COBs, you would have a very high PPFD, but the other way around and you would have a relatively low PPFD number.

 

[Rahz]

What PPFD would COB's running at 37Watts spaced 1 COB/sqft produce? At this level of PPFD will charging the room with CO2 be benificial vs the cost of generating it?

What cob are you asking about?

I'm not knowledgeable enough to tell you how to utilize CO2 properly in regard to the question. Good question though, might need someone specifically qualified to answer it. My understanding is that it produces a more pronounced effect as the PPFD is raised but I'm not sure there's any point at which it wouldn't have an effect and I assume a small bump in production would cover the cost of the CO2. Those I know who have used it ran sealed rooms and that seems like a reasonable way to keep the CO2 where it's wanted, but it requires a closed AC path and that can be more complex than some care to deal with.

 

[ttystikk]

Fair point, actually stupid assumption from me.

I looked into it more, yes they don't pull data off the sensor during directional gasses/high wind.

It's also consistent with other labs around the world.

Now that i think of it,the middle of the pacific ocean might be a good place to read air quality when the islands don't trade heavy winds. View attachment 4015997

Love that chart!

I find the differences in total quantity and especially seasonal variability fascinating.

 

[waveman]

@waveman - PPFD is dependent on the optics and distance from the light source. In other words, if you focused the COB beam angle very tightly (e.g. 15 degrees) and placed your plants very close to the COBs, you would have a very high PPFD, but the other way around and you would have a relatively low PPFD number.

I'm still designing the room but have been limited by my transformer to 20kW in the flowering room so I'm trying to maximize production from there with out spending 50 grand on lights and needing the propane truck to deliver gas too often. I've been recommended luminus cxm 22, vero 29, and citizen gen 6 as good candidates as I'm going for 1 COB/sqft with lower wattage I'll need a lot (504)

 

[ttystikk]

I'm still designing the room but have been limited by my transformer to 20kW in the flowering room so I'm trying to maximize production from there with out spending 50 grand on lights and needing the propane truck to deliver gas too often. I've been recommended luminus cxm 22, vero 29, and citizen gen 6 as good candidates as I'm going for 1 COB/sqft with lower wattage I'll need a lot (504)

Time to start thinking in terms of amps of power draw. Your transformer has a specific amp rating at whatever voltage- which depends on your service.

 

[KonopCh]

What about autoflowers and DLI, PPFD... they run at 18/6, 20/4, even 24/0.

 

[Photon Flinger]

I'm still designing the room but have been limited by my transformer to 20kW in the flowering room so I'm trying to maximize production from there with out spending 50 grand on lights and needing the propane truck to deliver gas too often. I've been recommended luminus cxm 22, vero 29, and citizen gen 6 as good candidates as I'm going for 1 COB/sqft with lower wattage I'll need a lot (504)

Do you have land space to put up a wind turbine? Or even solar panels? Offsetting the power draw with alternative energy might be a solution to your problem.