Contact Us
Want to advertise here? Contact us today to begin

Stoping Co2 Two Weeks Before Harvest Question!

Discussion in 'General Indoor Growing' started by HappyMonkey, Jan 18, 2019.

  1. Hi : ) So the question is:
    Do you stop using CO2 two weeks before harvesting?
    I know some people are! Do you guys know if it's better and why?
    Thanks for your time!
     
    3 balls likes this.
  2. 3 balls

    3 balls

    342
    641
    93
    I run it all the way to chop with no problems. I wouldn't swear to the benefit though. In my opinion CO2 might be the least understood component of an indoor grow. The finer details of it anyway. Maybe somebody smart will post some scientifics?
     
    HappyMonkey likes this.
  3. 3 balls

    3 balls

    342
    641
    93
    I was hoping somebody smart might chime in for my benefit as well. Maybe a fresh post will get more looks.

    Thinking about it a little more, I did remember a couple things.
    There are sealed rooms and then there are SEALED rooms, if you're anywhere close to airtight it could be a problem to shut it off. Just like we will use up all the oxygen in a sealed room and suffocate, the same could be an issue for plants.
    Another thing from my own experience that I have settled in on is 1000ppm. I have read enough people posting that they see little to no benefit from CO2 that I figure at 1000, I'm still double what I would be without it. You also have 1/3 less heat created by burners with 1/3 less LP or NG usage than 1500ppm. Or 1/3 less trips if using tanks.

    Anybody have some CO2 knowledge/experience to share?
     
    HappyMonkey likes this.
  4. Plants are not really using CO2 or any nutrient in large amounts the last few weeks of flower because they are in the process of dying. I don't think you will find any difference however if you do run it all the way through. If you have a sealed room, you will be able to tell that it isn't needed because your ppm's will not decrease very much.
     
    Growster240, 3 balls and HappyMonkey like this.
  5. This is what i am afraid of, that they will suffocate, it's a little crowded in there and it's properly sealed..
    I am not using a burner right now, but refillable tanks at 1200 ppm so it's a little pricey!

    Thanks for taking the time!
     
    3 balls likes this.
  6. Thanks : ) Much appreciated! Will watch my ppm's closely!
     
    3 balls and Homesteader like this.
  7. If you wanted to see the amount the plant is using, I would drop the CO2 down to 800 or 1000ppm and then close the tank and see how long it takes to get down to ambient (around 400ppm indoors) If you are using soil, chances are the microbes are helping you out as well and producing a healthy amount of CO2 from the soil, so the chances of exhausting all of it is unlikely IMO.
     
    3 balls and HappyMonkey like this.
  8. Good call, thanks, i will do that! Yes i'm using soil : )
     
  9. 3 balls

    3 balls

    342
    641
    93
    @Glow, HappyMonkey and I have some questions regarding CO2 usage and could use your scientific perspective.
    1. In what parts of the life cycle is enrichment of most and least value?
    2. I have read on another site that you will not see any benefits unless your temps are 85+, is this nonsense?
    3. Is there any benefit to adjusting ppm at certain points?
    Thank you!
     
    HappyMonkey likes this.
  10. Glow

    Glow

    145
    189
    43
    I actually have a pretty informative article on my site under advanced growing about all of this. The temperature thing is a myth actually although under elevated CO2 the plant can take a bit more heat than would otherwise be tolerable.

    1. In what parts of the life cycle is enrichment of most and least value?

    At all parts but at some point cost of CO2 has to be considered so many growers only elevate CO2 during flower. Also because elevated CO2 makes the plant grow more quickly a lot of growers don't like to elevate CO2 during stretch.

    3. Is there any benefit to adjusting ppm at certain points?

    As a general rule because photosynthesis and carbon petitioning is increased in elevated CO2 it is wise to increase ppm to accommodate for this. In fact, research has shown that particularly N and P demand is increased. The easy fix though without getting too technical is increase ppm (BTW I don't like ppm as a measurement because there is no universal standard so I like to talk in EC).

    I'd read the article I posted to get a better idea. CO2 enrichment isn't for everybody and far too many get it wrong.
     
    HappyMonkey and 3 balls like this.
  11. 3 balls

    3 balls

    342
    641
    93
    Awesome, I read most of the topics but have trouble scrolling down that page. Thank you

    Check this out Happymonkey

    https://medteknutrients.com.au/co2-enriched-hydroponic-growing/
     
    HappyMonkey and Homesteader like this.
  12. My plants always use the most CO2 during the first three weeks of flower by several hundred ppm per hour.
    Without getting too technical though Ill try to think through my screaming children.
    The first limiting factor is light. No light=No photosynthesis. Light creates light dependent reactions within the plant. The more photons the more ATP and NADPH is produced. These light reactions will eventually plateau and become limited by the next factor which is CO2. The Carbon in CO2 will produce the carbohydrates within the plant until this too plateaus. Temperature does not effect the light dependent reactions from photons but it does effect the light independent reactions. These reactions are made by enzymes in the plant that have an optimum temperature to do so depending on the species. It is hard to pinpoint for sure but anywhere between 77-85 seems to me to be optimum. Once the temp goes beyond this point, it begins to effect it negatively. Get all three on point and you can't do much more.
    download.jpeg
     
    3 balls and Glow like this.
  13. Glow

    Glow

    145
    189
    43
    Temperature is absolutely critical in the light dependent reactions because temperature affects the ability of rubisco to catalyse CO2. In fact the most important factor in this process is by far temperature.
     
  14. Glow

    Glow

    145
    189
    43
    3 balls likes this.
  15. Not sure where you learned that but the Calvin cycle is made up of 3 light independent reactions. Rubisco catalyses CO2 in the Calvin cycle.
    https://en.wikipedia.org/wiki/Light-independent_reactions

    "Although the light dependent reactions of photosynthesis are not affected by changes in temperature, the light independent reactions of photosynthesis are dependent on temperature."
    http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/068/Rate of photosynthesis limiting factors.pdf
     
  16. Glow

    Glow

    145
    189
    43
    Ah I see you've sort of oversimplified or not quite understood. Rubisco also processes oxygen in photorespiration - at higher temperatures photorespiration (which is wasted energy in photosynthesis) increases while the processing of CO2 by rubisco decreases. And yes I know all about the dark cycle (Calvin Cycle) but what you are missing here is that CO2 synthesis occurs during the lights on hours where the plant processes CO2 and releases oxygen. During the night the plant breathes oxygen and releases CO2 (put simply)

    Bit of a read for you (I'll try to find some more simple articles that may help also)

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC27241/

    Net photosynthesis (Pn) is inhibited by moderate heat stress. To elucidate the mechanism of inhibition, we examined the effects of temperature on gas exchange and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activation in cotton and tobacco leaves and compared the responses to those of the isolated enzymes. Depending on the CO2 concentration, Pn decreased when temperatures exceeded 35–40°C. This response was inconsistent with the response predicted from the properties of fully activated Rubisco. Rubisco deactivated in leaves when temperature was increased and also in response to high CO2 or low O2. The decrease in Rubisco activation occurred when leaf temperatures exceeded 35°C, whereas the activities of isolated activase and Rubisco were highest at 42°C and >50°C, respectively. In the absence of activase, isolated Rubisco deactivated under catalytic conditions and the rate of deactivation increased with temperature but not with CO2.
     
    Last edited: Jan 20, 2019
    HappyMonkey likes this.
  17. I really don't come around here to argue with anyone or measure anything against anothers but I wish you well on your website. I didn't get a chance to check it out but I'm sure its great.
     
    Glow likes this.
  18. 3 balls

    3 balls

    342
    641
    93
    The issue could be on my end but when I cursor over the Grow Info and the topics display, I cant mouse over to the scroll without the display retracting. Sorry, my computer terminology is as bad as my horticulture terminology.

    Speaking of CO2 in the first three weeks, Glow's site mentions that some people will skip elevating the CO2 at the first part of flower as not to encourage stretch. A really interesting strategy I never would have thought of.
     
    HappyMonkey and Glow like this.
  19. Glow

    Glow

    145
    189
    43
    Hey mate I don't see it as arguing or it certainly shouldn't be - it's in the interests of education to pick up on information which could lead growers to less than ideal practices. Plant science/physiology is extremely complex and often people pick up on one thing without understanding there are other important physiological processes in play. Its really that simple. Thanks on the site. That info has been in cyberspace for years and growing as I write. I published a book on indoor growing about 20 years back now and I have written ever since free of charge for the community. Plant science is my thing - I'm a weirdo lol - and I don't want to come across as argumentative or condescending. The point really is though that temperature plays an absolutely critical role in the light dependent reactions of photosynthesis. It's actually one of the myths of CO2 growing in that you should grow at far higher temperatures. That's not strictly true - what is true is that a plant is a little more tolerant to higher temperatures but that doesn't make it ideal where the rate of photosynthesis is concerned. In fact let me put in an image that I use in something I have written on CO2, light and temperature. This graph shows how photosynthesis peaks under elevated CO2 at a certain temp and then the rate of photosynthesis rapidly decreases under warmer conditions ====
    Source: Chandra, S. Lata, H , Khan, I. A. and Elsohly, M. A. (2008) Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions

    Screenshot (15).png
     
    Last edited: Jan 20, 2019
    HappyMonkey and 3 balls like this.
  20. Glow

    Glow

    145
    189
    43
    Yes its not desirable to promote high rates of growth when the plant stretches because the aim is to reduce stretch and not to encourage it.
     
    HappyMonkey and 3 balls like this.