As the title suggests I don’t know what Vpd range I should be dialing in to at this stage of my autoflowers. Any opionions will be appreciated! @ChittyChittyBangin
3 Likes
VPD 1 to 1.5 is where you should try to be at this stage…
4 Likes
Honestly, i got tired of chasing vpd. I just watch my humidity and slowly raise my ppfd over the period of 4 weeks to where at week 5 of flower im at 1000 ppfd if not a little more. All depends on how the plants take it. Since youre in flower , humidity 50 to 60 and temps 75 to 80. About weeks 7 start dialing your lights down to click or 2 so at week 8 or 9 youre around 700 ppfd
3 Likes
If me I would set the low trigger at 1.0 and the high trigger at 1.2 at that stage. Low trigger is sets off the exhaust and the high trigger the humidifier. That’s how I have mine set up.
Here is a link to that has a calculator to target the leaf VPD. Typically, the temp of the leaf will be 1-2 degrees cooler than the atmosphere in your grow space.
2 Likes
Couple things you want to be doing in order to avoid confusion & heading off-track.
You want to be adjusting your Leaf VPD number & not your not your air/room VPD towards your VPD target numbers, so you want to know your leaf temperature & leaf temperature offset in order to do that.
You also want to know your leaf temperature offset in order to pick the correct matching static VPD chart &/or to program the offset in any vpd controllers.
Leaf temp - Air temp = Leaf Temperature Offset
(Values can’t be swapped, & the answer could be negative & if so should be expressed as such.)
I like the Dimlux calculator, & also this active chart:
Active Leaf VPD Chart
I have noticed with the dimlux calculator sometimes you have to refresh it between calculations if you’re running a few calculations in a row, or I have seen it start screwing up in the past, after I ran three or four+ calcs in a row without refreshing it.
2 Likes