The facts about CO2 ppm: don't use 1,500!

[IMO]

do you have a special setup for co2 dispersion throughout the room or do you just rely on airflow? ty for all the info/help - you do an incredible amount of legwork... we are SPOILED

 

[the_extremist]

I zip tied the hose from my regulator to the back of an oscillating fan. Works like a charm.

 

[houdini]

Spurr, I think I may have a related problem....

Spurr, I think I may have a related problem....

Hi Spurr, I’m on my knees ! This problem has beaten me so far and ANY help/advice would be hugely appreciated. I know this post should be in Infirmary but your posts on CO2 make me suspicious I may have an environment problem

I moved to a new indoor grow location some months ago for security reasons after 5+ years happily growing in my original place.

The intention was to grow out some new mothers and use the clones for my grow. The seeds I’m using are C99 f1’s and a cross of c99 x lavender which I created myself. I should point out that the seeds were created outdoors.

New room is 15 ft. x 20ft. Temps. are 25-26 deg. C. Humidity is about 50%. Co2 levels are about 1000ppm, dehumidifier working, fans circulating air. I’ve outfitted the place with 6 x 1000w HPS, but am presently using a bank of 36W daylight acquarium flouros at 4300 lux each for seedlings with the intention to shift the seedlings under one of the HPS when they are 5-6 weeks old. Note that this is my second attempt to grow seedlings here; my first attempt produced plants that were so chlorotic that I dumped them after repeated attempts to cure them.

Right now I’ve 20 new seedlings in 6” pots a couple of weeks old. The soil is virgin Atami janeco light mix NPK 12-14-24. On my previous attempt I used Atami kilo-mix, which is a hotter version of the light mix. The plants are being watered with ph adjusted water. No nutes added. Runoff is about 6.8 ph and EC is about 1.2 mS, a little high but o.k. nonetheless.

The new seedlings are beginning to show signs of leaf chlorosis, from about the third set of leaves. I’m stumped. So what have I tried ?
- Chlorosis, to my knowledge, is caused by several things :
- A nutrient deficiency of either iron, magnesium or manganese. I’ve added a plant ‘tonic’ product last time round which contained chelated iron, mag., and mang. It didn’t make any difference. And why should it ? New soil should have these elements.
- Were my plants overwatered ? No, I let them nearly dry out between waterings and water sinks quickly through the soil.
- Bugs in the soil ? No, checked soil and plant roots. Besides irksome fungus gnats there are no other bugs.
- Maybe I put them under the HPS too early ? That’s possible but then when I backed off the HPS to 4ft. away there was no improvement.
- Maybe the air in the room is bad ? I’ve installed a powerful ventilation system which pumps air in 2 times per day for like, an hour each time.

Now here’s the thing : I decided to take one of the sick plants outdoors. It stayed in the same pot, same soil, the only thing that changed therefore was light, air and water. After 2 weeks of hardening off, hey presto, the plant leapt to life and began to produce green leaves and grow normally.

And heres another thing : I have one of the original chlorotic plants still growing in the room. I kept it to see its evolution over time. Its now grown to three feet and all the new growth is chlorosis free ! WTF ? And here I am……

Guys, if I could call in a pro I would, but for obvious reasons…my eternal gratitude and whatever else I can offer will go to someone who can solve or help me solve this riddle. Its costing me big-time.

 

[spurr]

Spurr,

Does barometric pressure play a role in a plant's growth and ability to photosynthesize? I read somewhere that grow rooms with intake fans that are more powerful than exhaust fans will create excess pressure in the grow environment which can be problematic.

Thanks,

b_d

Not to a large degree, as far as I know. I have not come across any data showing large effect on plants from various barometric pressures. I can look around for you, though.

 

[spurr]

Here are some screen shots from the following paper, thanks to the North Central Extension & Research Activity–101, the USDA - Committee on Controlled Environment Technology and Use.

The first shows how ~1,000-1,200 ppm is the point of saturation for most species that respond well to CO2 increases.

Chapter 4 - Carbon Dioxide
by Mary M. Peet and Donald T. Krizek
http://www.controlledenvironments.org/Growth_Chamber_Handbook/Ch04.pdf

From: Plant Growth Chamber Handbook
Langhans, R.W. and T.W. Tibbitts (eds.). 1997.
North Central Regional ResPubl. No. 340, Iowa State Agr. & Home Econ. Expt. Stat. Rpt. No. 99, Ames.
(full text) http://www.controlledenvironments.org/Growth_Chamber_Handbook/Plant_Growth_Chamber_Handbook.htm


​

--------------------------------------------------

--------------------------------------------------

--------------------------------------------------

 

[spurr]

thanks for all they great info.

I have a question about the day night co2 levels. I run 2 sealed rooms on a flip flop that are constantly exchanging air with eachother. I do this for cooling purposes, each side has a minisplit that the lights off room helps cool the lights on room. Plants are currently getting co2 24/7 at 1500 ppms. Has been working great for me so far. But if I can make the plants happier, im all ears.

With my setup what would you suggest I set my co2 at to balance out the good/bad? If you could choose only 1 ppm setting for day/night what would it be?


Thanks

Hummm. That's a good question, I would suggest 500-600 ppm. Yield increases in various flowering and fruiting plants, from ambient ~350 ppm to ~700 ppm, are commonly > 25-30% over plants at 350 ppm. It's the effects on plants from long term high CO2 at night that is the concern ...

I can upload the screen shot from a good study (by Dr. ElSholy (sp?)) showing increase in rate of photosynthesis when CO2 increases, as well as when temp increases and light strength (irradiance) increases.

 

[spurr]

Sick thread as always spur. thought you might like this:

btw i peak at 1200, not 1500. But otherwise i like the chart.

Hey buddy,

Thanks for thinking of me, and I don't want to seem like a dick, but I don't agree really anything on that chart. Mostly, I don't ascribe to the idea of tapering off everything near harvest and it appears that is how the chart was designed. That and the issue of VPD (Vapor Pressure Deficit) is apparently lost on the folks who made that chart.

What I don't agree with is mainly how things are increased then decreased. That and due to the increase and decrease many values are sub-optimal, at least to my understanding of plant science and cannabis. It appears as if the folks who made that chart chose values without much understanding of plant science, or at least without scientific validation. Ex., pH starting at 6.3 and then being reduced down to ~5.7 by the time harvest is near.

I would caution you from following that chart. I do realise can get good plants from following their chart, but you can also get good plants using Miracle Grow (with some slight adjustment). To get the highest ROI, yield, growth rate and reduction in losses, I would not follow that chart.

 

[spurr]

i heard somewhere (i think the seemorebuds dvds) that you should match your nutrient ppms to your co2 ppms. so, technically where people peek at 1200 ppms and gradually taper down... it makes sense.

I'm not much of a believer in the 'taper down' paradigm, except for EC

 

[spurr]

if your temp is lower maybe you don't need as much CO2?

If temp and CO2 are not near the ideal range then rate of photosynthesis is not as 'high', and the goodies that comes along are not as good.

We don't need CO2 to grow at day temps of (for example) ~80-84'F, but adding CO2 can offer many benefits.

 

[spurr]

I zip tied the hose from my regulator to the back of an oscillating fan. Works like a charm.

^^^ Yea that, me too.

 

[desertsquirrel]

Hey buddy,

Thanks for thinking of me, and I don't want to seem like a dick, but I don't agree really anything on that chart. Mostly, I don't ascribe to the idea of tapering off everything near harvest and it appears that is how the chart was designed. That and the issue of VPD (Vapor Pressure Deficit) is apparently lost on the folks who made that chart.

What I don't agree with is mainly how things are increased then decreased. That and due to the increase and decrease many values are sub-optimal, at least to my understanding of plant science and cannabis. It appears as if the folks who made that chart chose values without much understanding of plant science, or at least without scientific validation. Ex., pH starting at 6.3 and then being reduced down to ~5.7 by the time harvest is near.

I would caution you from following that chart. I do realise can get good plants from following their chart, but you can also get good plants using Miracle Grow (with some slight adjustment). To get the highest ROI, yield, growth rate and reduction in losses, I would not follow that chart.

The chart is from current culture H20, makers of the under current. I can tell you that although everything but the co2 taper is strictly for the UC, and its spot on other then peaking at a tad too high. The UC is a different animal, i would never do that in coco or rockwol.

The co2 i all ways have to taper off or flowering never finishes.

 

[Mister_D]

Well spurr you've done it again, my mind is offically blown. Seriously though thank you so much for all that you contribute. I have found many of the things you post about simply through much trial and error, but it is amazing to have scientific confirmation that i'm not totally crazy. Plus I love understanding the mechanics of how or why something works. The information you contribute to this site will/is helping many growers produce a better healthier product for themselves and the public at large. While also saving them money on inputs and reducing the amount of wastes introduced into the enviroment. I cannot thank you enough for posting your references as most growers I know are drones that believe anything the nute companies, and ed, jorge, etc, tell them. It is very difficult to argue with hard science, so I refer people to your posts and references when they don't take me serious. Again thank you for the time you put in to teach us laymen a better way.

 

[Sam the Caveman]

I was looking at co2 controllers and saw that CAP is making a pre-set version thats about $200. Its made for the natural gas or propane burners. The thing is, they are pre-set at 1450ppm.



ps- I've suspected for a while now that 1500ppm was too high when I read multiple people say they saw no difference running 1000ppm down to 600ppm

 

[spurr]

I was looking at co2 controllers and saw that CAP is making a pre-set version thats about $200. Its made for the natural gas or propane burners. The thing is, they are pre-set at 1450ppm.



ps- I've suspected for a while now that 1500ppm was too high when I read multiple people say they saw no difference running 1000ppm down to 600ppm

Don't do this ... do this (after you read the following)

I contacted HydroInnovations about their controller some time ago. I think CAP ripped off the idea from HydroInnovations (HI) because HI has been selling a very similar unit for some time. It's like $280 at Horticulture source and preset to turn on at 1,300 ppm and off at 1,500 ppm.

​

However, when I quarried about how one could hack the unit to turn on at 900 ppm and off at 1,100 ppm I was told it's very easy to do. They were going to send me schematics, but they then told me it's so easy schematics aren't needed. I was told one can open the back case and figure out what to do, after reading the manual.

That means auto-CO2 control for tanks or burners, for < $300! Of course, I would suggest contacting the nice folks at HydroInnovations about this issue before buying a unit.




PS. I use a CHHC-4 for CO2 control, but I suspect it's not all the accurate in reading CO2. I need to do some research to see the best way to measure CO2. Within the most recent PDF I hyper-linked to in this thread, there is lots of info about the best way to measure CO2.

 

[spurr]

The chart is from current culture H20, makers of the under current. I can tell you that although everything but the co2 taper is strictly for the UC, and its spot on other then peaking at a tad too high. The UC is a different animal, i would never do that in coco or rockwol.

Good point .

 

[Scrogerman]

Nice thread, Thanks Spurr.

 

[Capt Cannabis]

Good information, tagged for future reference

 

[Sideways]

Great info spurr- I am new to CO2 and just wanted to clarify- CO2 levels shoud be kept constant through all vegetative and flowering stages, with no taper down near the end?

Thanks!

 

[spurr]

Yes.

 

[Player2]

Jumper settings for the HydroInnovations CO2 Monitor

Jumper settings for the HydroInnovations CO2 Monitor

Thanks to Spurr we all now have another good adjustable CO2 controller option.

The "hack" is simple, just jumper settings, but the instructions provided by support are incorrect. I sent a revision back to them so hopefully this error has been fixed for the next person who asks.

So, the correct jumper settings are;
J1-disconnect;J2-disconnect CO2≤700ppm,the relay turns on, CO2 ≥900ppm,the relay turns off

J1-disconnect; J2-connect CO2≤900ppm, the relay turns on；CO2 ≥1100ppm,the relay turns off

J1-connect; J2-disconnect CO2≤1100ppm, the relay turns on；CO2≥ 1300ppm,the relay turns off

J1-connect; J2-connect CO2≤1300ppm, the relay turns on；CO2 ≥1500ppm,the relay turns off

Factory jumper settings

Jumpers modified for 900 to 1100ppm CO2(J1 is parked, could be completely removed if one could keep from losing it.)

If you are sent the instructions stating J4 and J5, do not use the header on the daughter board. The instructions above are correct. Daughterboard header 9 and 10 shorted for 10 seconds will reset the calibration of the CO2 module, although you probably shouldn't be messing with it. Do it outside and don't breathe on it if you do.

Your warranty was voided by just thinking about doing this