1K per m^2

1K per m^2, anyone done it?

The reason I ask is because I believe it's what's really required if you're going to increase CO2 and run high temps.

I mean I've heard 2000umol/s/m^2 at 1200ppm CO2 and I think 1500umol/s/m^2 at 800ppm CO2 as optimum for cannabis growth from a few different government studies. Both were at 85F(30C). One was like 50% humidity and the other I can't remember or they didn't say.

Mind you, 50% humidity is way too low for those temps to get adequate VPD. In the first weeks of flower if I run 85F and 1200ppm CO2 my leafs are at 83F and calculating VPD yada yada humidity should be 80-90%. to get in the 1.25 (not even like .8-.9 where it's optimal) Of course running higher humidity later in flower may lead to issues with mold, and it may reduce trichome formation but I've not tried it.

I think, though, that unless you're running 1k per m^2 that 85F is too high and may lead to stretchy plants and airy buds with traditional lighting recommendations (~60w per sqft etc.). 1200ppm CO2 probably wont matter as the carbon filter will remove any ethylene gas buildup that causes the negative side effects from running too high of a CO2 level in other crops.

So, right, why 1k per m^2?

Well for an example the Hilux grow by ushio (just a random bulb I picked) has 1810 mmols/s which I think is supposed to mean micro(u) but they left it as m for milli on their site. So lets say your reflector is 85% reflective then you have (1810*.85)=1538.5 micromols/s and over a m^2 you get 1538.5umol/s/m^2 so perfect but I imagine you're using air cooled hoods because if you're supplementing CO2 and using 1k/m^2 that's a crap ton of heat for an A/C. This will further reduce your light but oh well.

Anyone used the hydrofarm quantum par meter? just wondering if it's any good.

@Sativied and any other LED/lighting hero's who can give some input on this info. opcorn:

I'm not a lighting expert per se, but I've run a lot of lights of a lot of different types with a lot of different intensities. Some general personal observations;

1. PPfD is all plants care about. Lux, lumens, umols, all fail to measure the proper thing plants require.
2. PAR is one component of PPfD and intensity or 'irradiance' is the other.
3. CRI isn't very relevant, other than if it gets too low, PAR must also suffer.
4. If you want maximum GPW, run in the 400-600 PPfD range
5. Maximum growth is had at about 1500 PPfD but this is well past the point of diminishing returns for most. Consensus currently aims for 750-1250 PPfD, depending on goals and cooling capacity.
6. If a given light is more efficient, that is, emits more PPfD per watt than another, it will eventually be the cheaper choice no matter what the initial price premium.
7. Higher efficiency always means less heat per watt of power consumption in terms of HVAC requirements.

Apply these rules to whatever light you find. Everyone's goals are different, I've gotten out of the habit of attempting to apply my preferences to other people's situations and instead have begun to watch for the tools people use to tailor their cannabis growing system to their preferences.

@ttystikk so wait, isn't PPFD just the amount of par light reaching the plants? I guess I'm mistaken in my above post. What I meant was 1500-2000 umol/s/m^2 PPFD was found to contain optimum WUE et. al with enriched CO2 environment and temperature. We're assuming the light is measured at the canopy hence taking into account the area and the efficiency of the reflector. I understand there will be some losses due to walls or open sides where there is no overlapping light.

Where did 750-1250ppfd and 400-600ppfd come from? My next question was going to be that - IF growth is optimized at 1kW per m^2 with 800ppm CO2 and 85F @ 50% humidity then isn't that going to be the point of maximum return? I presume if you go over that then the return would start to diminish or if you're not quite hitting one of the factors that the return would start to diminish. E.g. you're running 85F with 1000ppfd and oops now you're getting airy buds. Is it strain dependent? Is it sativa/indica/hybrid dependent?

It'd be nice to generate a database among a collective of growers who are running sealed in the 400-2000umol/s/m^2 range, what CO2, humidity, temps, and yields per strain they are getting

Well the new DE HPS look to be the most efficient short term as I can see. Not sure if there's any decent air cooled ones though. Those bulbs are ~2100umol vs ~1800umol for a single ended bulb. I know COBs have some gains over that but glancing at the numbers there's a long ROI, a lot of DIY, and no one has really come up with a design to extract the heat from the grow room that they generate like with air cooled HPS.

ShirkGoldbrick said:

@ttystikk so wait, isn't PPFD just the amount of par light reaching the plants? I guess I'm mistaken in my above post. What I meant was 1500-2000 umol/s/m^2 PPFD was found to contain optimum WUE et. al with enriched CO2 environment and temperature. We're assuming the light is measured at the canopy hence taking into account the area and the efficiency of the reflector. I understand there will be some losses due to walls or open sides where there is no overlapping light.

Where did 750-1250ppfd and 400-600ppfd come from? My next question was going to be that - IF growth is optimized at 1kW per m^2 with 800ppm CO2 and 85F @ 50% humidity then isn't that going to be the point of maximum return? I presume if you go over that then the return would start to diminish or if you're not quite hitting one of the factors that the return would start to diminish. E.g. you're running 85F with 1000ppfd and oops now you're getting airy buds. Is it strain dependent? Is it sativa/indica/hybrid dependent?

It'd be nice to generate a database among a collective of growers who are running sealed in the 400-2000umol/s/m^2 range, what CO2, humidity, temps, and yields per strain they are getting

Well the new DE HPS look to be the most efficient short term as I can see. Not sure if there's any decent air cooled ones though. Those bulbs are ~2100umol vs ~1800umol for a single ended bulb. I know COBs have some gains over that but glancing at the numbers there's a long ROI, a lot of DIY, and no one has really come up with a design to extract the heat from the grow room that they generate like with air cooled HPS.

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You've made a lot of assumptions that are incorrect. The worst one is the very last one you made.

Lighting hero... that's just one letter apart from being the Flash so let me take a few minutes out of my busy schedule of protecting the community against evil Bibled influences. (Yeah I puked a little in my mouth there too )

When I read the title I thought you meant one kilogram yield on m2... I've seen a few 1k watt grows on 120x120cm but even those weren't really 1000watt (but dimmed), and no CO2 supplementing.

Here's a study you are probably referring to:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

ShirkGoldbrick said:

I think, though, that unless you're running 1k per m^2 that 85F is too high and may lead to stretchy plants and airy buds with traditional lighting recommendations (~60w per sqft etc.)

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What it clearly shows is that 30C at 1500ppfd is optimal. At lower ppfd, 30C is also always better than 25C.

Theoretically it could work with that ushio. A phillips de at 2100umol, minus reflector losses would still be too much... Unless you can drop the temp to 25c. At 25c increasing the ppfd after 1500 increases the photosynthesis rate, at higher and lower temps it does not. At 25C and 2000ppfd it still won't be better than 30C at 1500ppf though. Running anything over 1500 at 30c (86c) has a negative effect. 600ppfd and 2000ppfd has the same result at 30c.

Point is, that 30 is a given obvious optimal, and then 1500ppfd is optimal (at roughly 28 and 29 too). Even though that 500 extra going from 1000-1500 adds only about half of what you add going from 500-1000 and far less than the first 500. Which is related to where shittystick's 400-600 ppfd comes from, to an extend, the higher the ppf, the lower the gpw. The more light you add, the lower the postive effect of that addition, eventually it has a negative effect even. You get more from 1k watt on 5x5' than on 3x3 for that reason alone already. You get a higher gpw if you use minimal lighting. By lowering the 'w', not by increasing the 'g'...

While it's physically doable with the right strain (6x6 fat tall donkey dicks of about an oz each...) it's so impractical to grow a kilo or more on 1m2 so obviously increasing gpw isn't your goal. You would have to hang the light very low in a single bulb setup, and then it still won't be uniform, with major excess in the center. In case of a single m2 setup, if you want to run that high ppfd led is the way to go.

With many multiple overlapping bulbs and full climate control it could be done with crappy 1k watters. Efficient in terms of power usage it is certainly not, in more than just a couple of ways. Low gpw, but max possible gr/m2. And when you do have many bulbs, it would make more sense to use 1k watters with a better output than the one in your example, and then you don't need 1 per 1m2, more like 1.2m2.

They tested up to 750ppm CO2 (see table 2) which clearly showed positive results. 1200 seems high but I never really looked into supplementing CO2. I don't run sealed.

ShirkGoldbrick said:

sativa/indica/hybrid dependent?

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Yes. Hard to say how much. An afghanica from origin from colder regions will respond differently to certain temps than tropical sativas. The fact some are more drought resistant than others indicates it too. With the many pollenchucked polyhybrids your miles may vary even amongst phenos from the same pack. The best suitable variety would be one you create and select.

Sativied said:

Here's a study you are probably referring to:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf

That's one of them.

Point is, that 30 is a given obvious optimal, and then 1500ppfd is optimal (at roughly 28 and 29 too). Even though that 500 extra going from 1000-1500 adds only about half of what you add going from 500-1000 and far less than the first 500. Which is related to where shittystick's 400-600 ppfd comes from, to an extend, the higher the ppf, the lower the gpw. The more light you add, the lower the postive effect of that addition, eventually it has a negative effect even. You get more from 1k watt on 5x5' than on 3x3 for that reason alone already. You get a higher gpw if you use minimal lighting. By lowering the 'w', not by increasing the 'g'...

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The part that bothers me is they only tested temperature/ppf combinations. If you look down further for the table they have the photosynthesis vs CO2 concentrations and it doesn't say what lighting levels were used for that.

However, I did notice the biggest jump is between 250-350 which I expect because 250 is less than atmospheric CO2 so it probably stresses out the plant.

For the most part the data is insignificant because the increasing CO2 levels overlap once you include the error but if we ignore the error and look at the jumps listed:

350-450 is 0.12
450-550 is 1.78
550-650 is 3.94
650-750 is 6.32

The difference is larger as CO2 levels climb higher. Chandra did another study showing at 750ppm CO2 there can be a 48% increase in photosynthesis over atmospheric which is strain dependent.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550578/

I believe these are all synergistic effects and while I'm willing to bet that it's still a hyperbolic regression when you account for increased levels of CO2 (I'd like to see them go higher than 750 on that too - go until it has detrimental effects) I think the efficiencies probably change quite a bit.

Furthermore, I know there's plenty of people only using 500umol who aren't breaking a gpw but are doing plenty of other things right. The only I know of is Stoney419 over at icmag.

ShirkGoldbrick said:

The part that bothers me is they only tested temperature/ppf combinations. If you look down further for the table they have the photosynthesis vs CO2 concentrations and it doesn't say what lighting levels were used for that.

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Indeed.

From that CO2 specific research:
"plants were kept under strict controlled environmental conditions (25 ± 3 °C temperature and 55 ± 5 % RH). Indoor light (18 h photoperiod, ~700 ± 24 μmol m−2s−1at plant canopy level)" using hps.

But also:

"Photosynthetic measurements were recorded at steady state condition with the chamber air temperature maintained constant at 25 °C. Light (1500 μmol m−2s−1)" using led...

I think the ppf used for the test results in the table in the older research is 1500 (their concluded recommendation, and what they used in the newer CO2 paper). The temp should be 30 based on the first, but the newer clearly uses 25. If you would assume 25, and run 28, the ppf/temp graph could perhaps be used to roughly guesstimate the CO2 level.

The fact they used 750 as maximum is a strong indication that is high by itself, like using 30c in temp or 2000ppf. But, it could be based primarily on the prediction of outdoor CO2 levels...

Sativied said:

Indeed.

From that CO2 specific research:

"Photosynthetic measurements were recorded at steady state condition with the chamber air temperature maintained constant at 25 °C. Light (1500 μmol m−2s−1)" using led...

I think the ppf used for the test results in the table in the older research is 1500 (their concluded recommendation, and what they used in the newer CO2 paper). The temp should be 30 based on the first, but the newer clearly uses 25. If you would assume 25, and run 28, the ppf/temp graph could perhaps be used to roughly guesstimate the CO2 level.

The fact they used 750 as maximum is a strong indication that is high by itself, like using 30c in temp or 2000ppf. But, it could be based primarily on the prediction of outdoor CO2 levels...

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Well, 30 isn't exactly optimum. Here's some more research they did: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550580/

"To study the temperature response of photosynthesis in the different varieties ofC. sativa, leaves of each variety were exposed to 20 °C, 25 °C, 30 °C, 35 °C and 40 °C under controlled photon flux density (PPFD, 1,500 μmol m−2s−1, this light intensity is reported near optimum, Chandra et al.2008), humidity (55 ± 5 %) and CO2(350 ± 5 μmol mol−1) concentrations."

"Among the drug type varieties, optimum temperature for photosynthesis (Topt) was observed in the range of 30–35 °C in high potency Mexican HPM whereas, it was in the range of 25–30 °C in W1. A comparatively lower value (25 °C) for Toptwas observed in MX. Among fiber type varieties, Toptwas around 30 °C in Zolo 11 and Zolo 15 whereas, it was near 25 °C in Felinq 34 and Kompolty."

At this point I'm going to concede that there is no optimal unless you're talking about a specific clone only strain.

With that in mind, I still don't think 750ppm CO2 is that high as 1200 is maximal in a few other studies I've read for other crops. It becomes detrimental above 1200 as there's ethylene buildup but if you're running a carbon scrubber you wont have ethylene build up. Due to this I believe it's possible that the optimal CO2 is as high as your equipment allows you to go while maintaining ethylene scrubbing. Of course you will reach saturation at some point but I don't know what that is.

Furthermore, I think all the science behind this is sham. Let me explain.

The first data we looked at described an inverse hyperbolic curve for ppf/Temp. They showed what amounts to an exponential curve with CO2 enhancement but provided no light or temperature values. The temperature data I just posted is sound and I believe that different strains have different photosynthetic/cartenoid contents and different potentials for photosynthesis.

The part that really, really bothers me is the humidity. They maintained 55% in every study I looked at. At 85F 55% humidity is nowhere in line with VPD recommendations and will cause stomatal closure that may only be compensated for by increasing CO2. I think this causes the ppf/Temp curve to have lower efficiencies at higher lights/temps because the stomata are closing in response to a high VPD and so the plant can't keep up.

More light does not equal more yield, it equals deeper penetration.
Anything above 600w@1m^2 is an overkill.
See chart https://i768.photobucket.com/albums/xx322/hundredgramoz/1157989-Foot-Candle2520Chart2520HPS.jpg
PAR output is directly related to lumen output, so keeping a 400w bulb 12" away from the canopy tops (recommended distance) will give same amount of lumens as 1000w kept at 21".

1000w@1m^2 is a massive electricity hog as it requires lots of air cooling, don't do it.