HPS RH vs LED RH

ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
Frank Cannon said:
So if hps is hotter that will reduce humidity which should make VPD worse...
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You know it!

Frank Cannon said:
but because QB LED light is stronger and LST is lower it causes the plant to transpire at an abnormal rate...Random has tried alot to help me get this but I am thick...
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Lol me too, and that's what I used to think as well, but can't seem to figure why the RH is low? Shouldn't the RH be increasing with heavy drinking? That water has to go somewhere, right? That's where I'm getting stuck. :confused:

In my experience it seems LED is traditionally lower RH than HPS. And if this is true, and not just in my experience, but if there's a general trend, then it would make sense that adding RH to LED isn't helping because its over transpiring, but rather some other reason.

Frank Cannon said:
One thing I know is that plants under high QB light levels are very sensitive to nute levels compared to hps, but I am being tutored to run lower nute levels to compensate for this which is a reflection of higher VPD i.e. run lighter nutes to compensate for more water uptake. This has helped!
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Well I'm glad it's helping :) I think you need to add RH to LED too.
 
jarvild

jarvild

Well-Known Member
ChiefRunningPhist said:
Word thanks, before you had your nutes dialed in, did you ever notice anything different between the 2? RH, nute strength/ratio, anything?
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Yes, I experienced what most seemed too when switching to LED's. My first flowers under them I was ashamed of and I did the higher temp and keeping VPD in check as most state on here to do it helped some but didn't cure the underlying problem.
I'm sort of in trim jail right now, so if you want to converse later I'll explain my research and solutions at a later time.
20190317_203902.jpg
 
ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
jarvild said:
Yes, I experienced what most seemed too when switching to LED's. My first flowers under them I was ashamed of and I did the higher temp and keeping VPD in check as most state on here to do it helped some but didn't cure the underlying problem.
I'm sort of in trim jail right now, so if you want to converse later I'll explain my research and solutions at a later time.
View attachment 4303136
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Lol sounds good, get to work slave :bigjoint:
 
1

1212ham

Well-Known Member
Frank Cannon said:
So if hps is hotter that will reduce humidity which should make VPD worse... but because QB LED light is stronger and LST is lower it causes the plant to transpire at an abnormal rate which then makes the effects of Higher VPD worse than under HPS? buggered if I know either but I think this is what I should understand? Random has tried alot to help me get this but I am thick...
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Some VPD stuff in the following link. I found post #34 by Random particularly interesting! https://www.rollitup.org/t/need-help-best-lamp-project.984587/page-2
 
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