Vpd target vs Leaf temp.

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Aqua Man

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Please read that post I'm not going to answer anymore... cause now I'm just typing out everything I already have.
 
Veteran

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What chart? That's your problem you are using a chart... THEY ARE NOT ACCURATE you MUST calculate your own based on LEAF TEMP.
Well i dont use them and thats the point i try to make not to use them because most charts tell different values and the whole idea is bad. We should take another approach.
 
Veteran

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Please read that post I'm not going to answer anymore... cause now I'm just typing out everything I already have.
hey im not forcing you, thanks anyway for your input i appreciate it really, i will read it i didnt get the chance because i was in conversation with you buddy. Thanks .
 
Aqua Man

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hey im not forcing you, thanks anyway for your input i appreciate it really, i will read it i didnt get the chance because i was in conversation with you buddy. Thanks .
And I agree with you 1.6-1.8 under co2 is absolutely fine.

Under atmospheric a bit lower.
 
Veteran

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And I agree with you 1.6-1.8 under co2 is absolutely fine.

Under atmospheric a bit lower.
ok i read your post, its a nice post about what vpd is and that the goldilock zone is the zone you want to be. But i dont agree and thats what this post is about.
I just checked the room and vpd is 2.0 leaf temp is 26 c 78,8 F room temp is 29,2 C /84,5 F not in the goldilock zone right but still cool leaf temp and i think not a bad temp at all.
53902533 7BB8 4D25 90C0 B7DF221FDF92
53902533 7BB8 4D25 90C0 B7DF221FDF92
 
Aqua Man

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ok i read your post, its a nice post about what vpd is and that the goldilock zone is the zone you want to be. But i dont agree and thats what this post is about.
I just checked the room and vpd is 2.0 leaf temp is 26 c 78,8 F room temp is 29,2 C /84,5 F not in the goldilock zone right but still cool leaf temp and i think not a bad temp at all. View attachment 1123474 View attachment 1123474
You obviously did not read my post because your VPD IS 1.3!!!!!

YOU ARE CALCULATING IT WRONG.... which is why I made the post to start with because sooo many ppl don't get it....the results you are seeing from thise parameters fall exactly in line with VPD.

This is what happens when ppl rely on tech to understand something and don't take the time to learn it.
 
Aqua Man

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I should correct myself. You may have read but misunderstood what I wrote. Sorry been under a bit of stress lately so don't mean to be a dick but the calculations your using are not giving you the true VPD.
 
Veteran

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I should correct myself. You may have read but misunderstood what I wrote. Sorry been under a bit of stress lately so don't mean to be a dick but the calculations your using are not giving you the true
I should correct myself. You may have read but misunderstood what I wrote. Sorry been under a bit of stress lately so don't mean to be a dick but the calculations your using are not giving you the true VPD.
No man your not a dick at all im learning from you. You are right about the calculation i was just reading up numbers from a device im using but the numbers it shows are going up and down because of the rh swing the ac is causing. I should have wrote down the averages. 1,3 is indeed in line with Vpd. Thanks for your input im going to read again its not that simple. And the ideal leaf temps you mentioned for fotosynthesis got me thinking. So a leaf temp of 24 c/75F which has more evaporation then a leaf temp of 28 c/82F
in combination with 30c/86F ambient temp(1200 ppm Co2) is not better for fotosynthesis eventhough the evaporation is at a higher rate thus i would have thought more gas exchange. Also i read something about the nutrient uptake balance gets disturbed with a too high evaporation , it was between calcium and potasium im not sure which one was taken up more but one of those is taken up more than the other because the high Vpd. Now im getting closer to understand what vpd is all about and i hope others too. Thanks again buddy for the trouble.
 
Aqua Man

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No man your not a dick at all im learning from you. You are right about the calculation i was just reading up numbers from a device im using but the numbers it shows are going up and down because of the rh swing the ac is causing. I should have wrote down the averages. 1,3 is indeed in line with Vpd. Thanks for your input im going to read again its not that simple. And the ideal leaf temps you mentioned for fotosynthesis got me thinking. So a leaf temp of 24 c/75F which has more evaporation then a leaf temp of 28 c/82F
in combination with 30c/86F ambient temp(1200 ppm Co2) is not better for fotosynthesis eventhough the evaporation is at a higher rate thus i would have thought more gas exchange. Also i read something about the nutrient uptake balance gets disturbed with a too high evaporation , it was between calcium and potasium im not sure which one was taken up more but one of those is taken up more than the other because the high Vpd. Now im getting closer to understand what vpd is all about and i hope others too. Thanks again buddy for the trouble.
Yeah potassium has a large influence on water in the plant. With to low of transpiration rates calcium is often an issue so it's a balance. So yes with a high evaporation more calcium is taken up which can lower the availability of potassium because the kinda compete for uptake. It's all about balance
 
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The reason i started this thread is actually to find out which climate is better if you have to choose from 2 situations with the same vpd but different leaf temps. And the same with the same ambient temp and same vpd but different leaf temps and rh%.

excuse me for not being clear enough from the beginning because english its not my native language.

So we have a high temp 88F/31c
With low rh 44% leaf temp 77F/25c vpd 1.2

next air temp 83F/28c leaf temp 80F/26,5c
Rh 60% vpd 1.2

Next is the same air temp as first climate 88F/31c but different leaf temp 85F/29,5c rh 65% vpd 1.2

All the same vpd but still very different climates. Mine is high temp low rh and low leaf temp.
I like to hear which one you prefer and why. I want to point out that even if you have the same vpd you still can have a very different nute demand and different result. Mind boggling not? First i thought as long as leaf temp is ok vpd didnt matter but thats not the case. So we follow the vpd guide but still have different situations. I would think the climate with ideal leaf temp is the best , but what is your experience ? Who has better yields with higher leaf temps or lower?
 
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Aqua Man

Aqua Man

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The reason i started this thread is actually to find out which climate is better if you have to choose from 2 situations with the same vpd but different leaf temps. And the same with the same ambient temp and same vpd but different leaf temps and rh%.

excuse me for not being clear enough from the beginning because english its not my native language.

So we have a high temp 88F/31c
With low rh 44% leaf temp 77F/25c vpd 1.2

next air temp 83F/28c leaf temp 80F/26,5c
Rh 60% vpd 1.2

Next is the same air temp as first climate 88F/31c but different leaf temp 85F/29,5c rh 65% vpd 1.2

All the same vpd but still very different climates. Mine is high temp low rh and low leaf temp.
I like to hear which one you prefer and why. I want to point out that even if you have the same vpd you still can have a very different nute demand and different result. Mind boggling not? First i thought as long as leaf temp is ok vpd didnt matter but thats not the case. So we follow the vpd guide but still have different situations. I would think the climate with ideal leaf temp is the best , but what is your experience ? Who has better yields with higher leaf temps or lower?
Leaf temls of 75-80f work well for me I'd say 78-80f depending on strain. Imo we should look to adjust the leaf temp first and foremost and then adjust the humidity to reach a decent VPD. Sativas I found like the more humid end and indicas the less humid end of VPD. But by far the leaf temp is the most important and impact full for my experience.

This is with about 1200ppm of co2
 
Veteran

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Leaf temls of 75-80f work well for me I'd say 78-80f depending on strain. Imo we should look to adjust the leaf temp first and foremost and then adjust the humidity to reach a decent VPD. Sativas I found like the more humid end and indicas the less humid end of VPD. But by far the leaf temp is the most important and impact full for my experience.

This is with about 1200ppm of co2
Yes 1200 ppm co2.
 
iffey

iffey

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Great discussion you 2. My head is spinning as I read thru this thread but getting it ....some.. it'll sink in sooner or later.
I think I have a touch of AADD and following completly takes a couple passes thru the 'education material'. Thank you both.
 
PulsePeet

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Yes 1200 ppm co2.
With co2 you want higher leaf temps. Photosynthesis happens faster at higher temps with higher concentrations of co2. I believe ideal leaf temp might be close to 85f with 1200 ppm co2. This also assumes you have enough light to take advantage of the co2
 

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