Co2 and vpd?

Renfro said:

One thing about CO2 enrichment, the plants actually perform better if you have low points and high points. I wish that I could set a larger dead band on my CO2 controller personally but I can use periodic vent cycles on a timer to achieve the same thing.

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I am adding co2 to my flowering room I am finishing up. You saying get it back down near 400 ppm during lights off...or even some ramping up and down during on?

dbz said:

I am adding co2 to my flowering room I am finishing up. You saying get it back down near 400 ppm during lights off...or even some ramping up and down during on?

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I don't remember the exact science behind it but it had to do with the plants opening up their stomata and really working to get the CO2 during periods of lower PPM, then when you ramp it up they have a period of peak performance before they start to close up the stomata due to the surplus of CO2 available. There was someone that explained it better on here once so I started playing with it. I have found that it seems to benefit if you can have that occur more than just once a day at lights on.

pahval said:

yep, thats also a thing, co2 must be food grade... if you go with co2, you need more of lights and nutes... also, if you go with higher VPD that will mean plant will absorb more water, hence will absorb more nutrients, so be careful about it, maybe you just need to raise vpd (make plant intake more), or you keep same vpd as before co2 and enrich your nutrient solution more... anyway, im glad to help out! <3

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Someone can correct me if I'm wrong, but there is no need for food grade co2 in your grow room. Industrial co2 is fine, and is half the cost (at least where I get it from). Food grade is for home brewing. No different than if you are using a burner. Propane is propane.

Not related to the above comment, I'm also interested in why so many post say that you need to be running 85F - 90F when using co2. From what I've read, Co2 intake is all about correct VPD. I'll run higher (85f) when in veg just to save on cooling costs, but there are different vpd pressure ranges based on how far along you are. The quality of my meds greatly increased when I started following the correct ranges for each range (veg, late veg/ early flower, late flower) versus trying to follow the same vpd range from start to finish. Just my experience anyways. That's why you need full control of your environment to be able to hit those set points for temp/humidity in flower. You should have the ability to pick a temp and be able to match the humidity with a few clicks. Most guys I see running co2 throw it into a room thats too hot and too dry and then expect a miracle.

Your lighting plays a huge part. I struggled to attain the proper vpd range when I was running HPS or CMH. Soon as I switched to LED panels my temps dropped by 2/3 and its a cake walk now.

Well, I did not use "food grade" CO2. Harvested 918g off 4 plants, from seed to harvest 17 full weeks. I'm happy with those numbers, im sure everything 100% perfect, I could have yielded more. My grow will never be 100%, so these numbers are great for me. Thanks to everyone that took the time to respond!!!!

mhalter81 said:

Well, I did not use "food grade" CO2. Harvested 918g off 4 plants, from seed to harvest 17 full weeks. I'm happy with those numbers, im sure everything 100% perfect, I could have yielded more. My grow will never be 100%, so these numbers are great for me. Thanks to everyone that took the time to respond!!!!

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Hey I know its alittle late, but there are a lot of calculators out there that actually require an input of air temp, and leaf temperature, and RH to calculate the offset and spit out the most accurate VPD number.

mhalter81 said:

Been growing for about two years now. Just started co2 recently, I understand that my temps need to be 82 to 85ish to take the most advantage of co2 enrichment. Is that room temps or canopy temps? Currently running 79 degrees in room humidity around 58 percent, canopy at 84-85 humidity much lower of course. According to the pulse vpd chart im good for room vpd and very poor considering canopy. Plants are looking very healthy, but im afraid im missing out on potential, or wasting CO2. Can someone please help?

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I use co2 bag and use VPD from growdoctor.com. Have the prettiest health plants. Also the website has a calculation for your nutrient mix. Very helpful site and this is my first time growing. DWC and looks to yield about 30 oz. Gonna try this water curing also. Saw that on another website and it makes a lot of sense. Might want to check it out. Good Luck