Is VPD/KPA important or does temp/rh matter more?

Growth · Nov 6, 2023

We're growing 4 auto-flower plants in an AC infinity tent with 2 fans, giant filter, light, and a humidifier.
All in 5 gallon fabric pots.

When we use suggested temp/rh on our plants it doesn't align with the temp/rh we're told to keep

I've seen people SWEAR by VPD and others just say keep it between X and X.

We're trying to keep our seedlings at 80F/60-65RH. We have the AC infinity app and it says our VPD is off of what it "should" be, so we're a bit confused.

Any tips on this and growing in general would be super helpful.

Thank you in advance.

Cannaburg · Nov 6, 2023

This is what I have gathered and could be told I'm wrong... vpd and all that basically keeps you in range for growth rate/speed...I personally never got into par reading ppfd vpd readings ever... I never even really ph'ed... I keep a low rh around 30% to prevent basement mold growths with temps between 68 and 72 degrees...
With that said I may be prolonging my veg process a bit but that.is all that it's hindering....

I'm sure I could be totally wrong or have a partial right in there... but others shall chime in....

I started in early 2000's so we didn't have all this "techy" stuff nor science based grows... but just learning what your plant "says" is key!

Growth · Nov 6, 2023

JKash said:
This is what I have gathered and could be told I'm wrong... vpd and all that basically keeps you in range for growth rate/speed...I personally never got into par reading ppfd vpd readings ever... I never even really ph'ed... I keep a low rh around 30% to prevent basement mold growths with temps between 68 and 72 degrees...
With that said I may be prolonging my veg process a bit but that.is all that it's hindering....

I'm sure I could be totally wrong or have a partial right in there... but others shall chime in....

I started in early 2000's so we didn't have all this "techy" stuff nor science based grows... but just learning what your plant "says" is key!

Well we have a tent in the basement and it's air tight that's why we keep the RH 60-70. We're keeping the temp between 70-80.

Which at the moment is...
80F/70RH = 1.00/kpa

Apparently it's supposed to be .04-.08 right now. Not sure if I should just leave it or try to correct for the right VPD.

Wuddup_B · Nov 6, 2023

I can't totally control it so I compensate. High vpd, lower feed (ec) and needs more water. Low VPD, increase feed.

Ive read a study that showed high vpd can potentially give better yields if you get the feeding down.

Growth · Nov 6, 2023

Wuddup_B said:
I can't totally control it so I compensate. High vpd, lower feed (ec) and needs more water. Low VPD, increase feed.

Ive read a study that showed high vpd can potentially give better yields if you get the feeding down.

I'm not even totally sure what VPD is lol

Our medium has enough nutrients to last until budding stage according to the guide my brother followed.

But, all I know is it's supposed to be .04-.08 and it's 1.00ish

Cannaburg · Nov 6, 2023

Ok don't worry about vpd... if you don't even understand it yet it's not worth getting into at this point... I would just focus on your temp and rh control.... those are what can cause some of the major problems... mold growth...freezing...scorching heat.... learn the basics 1st before getting into the nitty gritty fine tuning of environment control such as vpd

Cannaburg · Nov 6, 2023

I have a simple basement grow 1 tent and 1 non tent... I have a dehumidifier to keep rh down in my grow areas.. like 30%... 4 plants yielded me over 2 lbs... I don't know vpd...par levels...ppfd grids... or any of that... my lights are connected to an analog wall timer... no wifi stuff or nothing... my fans run 24/7 lights on or off...
Focus on plant training for yields environmental control gets you boosts in yields.... if I had perfect environment and had perfect vpd...and maybe some co2...that 2lb harvest could have been maybe 2.5 lb harvest instead?!?!

Growth · Nov 6, 2023

JKash said:
I have a simple basement grow 1 tent and 1 non tent... I have a dehumidifier to keep rh down in my grow areas.. like 30%... 4 plants yielded me over 2 lbs... I don't know vpd...par levels...ppfd grids... or any of that... my lights are connected to an analog wall timer... no wifi stuff or nothing... my fans run 24/7 lights on or off...
Focus on plant training for yields environmental control gets you boosts in yields.... if I had perfect environment and had perfect vpd...and maybe some co2...that 2lb harvest could have been maybe 2.5 lb harvest instead?!?!

I heard the C02 of you just being near them taking care of them is more than enough and there's no need to buy the packs of it.

2Water · Nov 6, 2023

Make sure you are adjusting the air temp differential in the settings. My air temp is usually about 4 degrees hotter than leaf temp. Changes the vpd. I am one of the growers that swears by vpd and I use the AC infinity controller. Basically vpd affects the rate at which the plant can transpire. Depending on stage of growth, manipulating the vpd can keep the plant in the optimum transpiration rate for growth. With all that being said, you really have to have everything else dialed in first before it will makeca difference.

Cannaburg · Nov 7, 2023

Growth said:
I heard the C02 of you just being near them taking care of them is more than enough and there's no need to buy the packs of it.

I don't use co2... I heard the co2 mushroom packs were garbage for co2... co2 is good if your running hotter temps as well

Is VPD/KPA important or does temp/rh matter more?

Is VPD/KPA important or does temp/rh matter more?

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Cannaburg

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Is VPD/KPA important or does temp/rh matter more?

Is VPD/KPA important or does temp/rh matter more?

Growth

Cannaburg

Can you out GRAV The Gravmaster???

Growth

Wuddup_B

Growth

Cannaburg

Can you out GRAV The Gravmaster???

Cannaburg

Can you out GRAV The Gravmaster???

Growth

2Water

Cannaburg

Can you out GRAV The Gravmaster???

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