[Whelm]

Greetings,

This following was posted by me as part of a larger thread in the room design section, but I am very curious about this and it fits better in this section anyway.

My partner has a master's degree in plant science. When I spoke to her about the conventional wisdom that 1500ppm co2 is ideal, she asked what proof I had to back up this claim. I realized that I have no actual proof. I have never used co2 and have only heard anecdotal evidence, though lots of it. Many people claim yield increases but I cannot find any grow logs showing side by side grows where the only variable is co2 added in one space, none added in the other. Everyone claims 1500ppm adds 20-30% to final yield, but non-anecdotal proof seems lacking. I recognize that there is a lot of anecdotal evidence, but how much of this is the placebo effect combined with growers paying extra close attention to all details, thus boosting yield.

My partner has access to all scientific journals and researched the issue. There are numerous studies on the effects of co2 that are not anecdotal. For C3 plants like cannabis, science tells us that adding co2 has a substantial positive vegetative effect, increasing leaf and stalk growth rate and size. In the flowering stage though (once flowers start to form), added co2 has a neutral to negative effect. In other words: great for veg, bad for bloom. In other other words: it is possible that any increase in overall yield has to do with creating bigger, healther plants in veg that then finish bigger, as opposed to co2 having a positive effect in bloom.

A few questions:
1. Do you know of any scientific studies that state adding co2 is beneficial to the flowering stage of C3 plants?
2. Do you know of any grows that have done a side by side study of increased co2 vs no added co2 in bloom?
3. Have you used co2 exclusively in veg (not in bloom)? What were your results?

Thanks!

[supermanlives]

i had greenhouses . i know for a fact what it does. 1500 is overkill tho. i dont use co2 in veg as i get plenty free from my heater. old fashioned ng heaters.

[mcfly420]

The facts about CO2 ppm: don't use 1,500!
https://www.icmag.com/ic/showthread.php?t=221893

[dreadkush]

Co2 for sure helps and increases yield for sure

[Weird]

bottom line blow CO2 into your grow until it makes a noticeable difference because CO2 will make a garden noticeable different

unless it is throttled by some other condition

liken CO2 is like nitrous in a car

you dont put nitrous in a hooptie to make it a hot rod, you put nitrous in a hot rod if your looking to raise the bar

[Shcrews]

i would be down to check out a side-by-side... seems like most people just run one or the other though.

in my experience co2 definitely speeds up plant growth, which would in turn increase bud growth.

[mg75]

amongst other nutrients and additives, co2 will shorten your harvest time from 7-10 days. we use 1500ppm with great results. the fact that the sensor picks up 1500ppm does not mean it is 1500ppm all over the room and plants. with fans blowing, air leaks, plant usage and temperature/humidity variations we feel 1500ppm is a good number.

also...

if you run a sealed room (like we do), you must run co2 supplementation. sealed rooms are the best and most efficient/safe way to run a grow op. the fact that i can control everything in it, is golden. no air-born spores nor pests. zero smell on the outside. complete temperature/humidity control regardless of outside. co2 injection is essential in both veg and flower.

[lost in a sea]

everyone knows this its simple biology, co2 + h20 + light >>photosynthesis>> sugar,, which is then used by the by mitochondria to release energy by making ATP from it,, its a big part of why plants have stoma,,

even if your the shittest grower co2 will improve the plants yield,, maybe as a side effect to growth speed but its a subjective call,,

ive been adding co2 for over 10 years and i can say it makes life easier,, plants grow stronger, faster, healthier, the roots are happier that are near the surface, it inhibits pests, thicker stems (imo), but you still have to be able to grow good weed though to get the best from adding co2,,

just using a butane heater kicks out tons of the stuff,, but thats better for cold situations,, like living in the uk,,

it does definitely have a positive effect all the way through growth from day one sprouting till the end,,

1500ppm as metioned. much higher and you wont too much improvement,,

if used just in veg the plants would grow taller than normal and sooner but in my opinion it helps to let cannabis mature genetically for as long as possible before flowering to avoid hermie tendancies as much as possible, but if the veg stage was almost totally stress free you will be fine even if they are ready to go through a week earlier than normal,,

during veg the plants efforts and energy are on roots,, but the flowering time is when the plant needs sugar the most for manufacturing nugs,, so yeah benificial during both stages,,

[BigDawg]

isnt outdoor co2 only around 500?

[SacredBreh]

https://www.plantphysiol.org/content/94/4/1728.full.pdf

You have to have optimal light saturation and increased temp also... the temp part is not in this article.

Not directly related to C3.
https://www.publish.csiro.au/?paper=PP9840375

Peace