VPD confusion
- Thread starter Orin190
- Start date
Ed Rosestale
Member
That chart looks odd, it is most likely already recalculated to your LST which seems to be odd as well. You have 5 farenheit difference at 82 and humidity under 50. Thats a hell of transpiration for the plant, how do they look like?
effexxess
Well-Known Member
The controller reading agrees with the results from this calculator, FWIW.
pulsegrow.com
VPD Calculator
Solve For: Temp RH VPD Temp (F) Temp (C) RH (%) VPD Air (kPa) Leaf Offset (F) Leaf Offset (C) VPD Leaf (kPa)
pulsegrow.com
wtf is leaf offset and how did you come up with 2 degrees farenheit as the # to put in there?The controller reading agrees with the results from this calculator, FWIW.
View attachment 5306865VPD Calculator
Solve For: Temp RH VPD Temp (F) Temp (C) RH (%) VPD Air (kPa) Leaf Offset (F) Leaf Offset (C) VPD Leaf (kPa)
effexxess
Well-Known Member
"The plant’s experience is slightly different because they are usually a bit cooler than the room. If the plant temperature is exactly the same as the room temperature, then the plant and room Vapor Pressure Deficit levels are equivalent. But this is rarely the case! Usually, the leaves are between 3° and 5° F cooler than the room because they are transpiring. The evaporation on the leaf’s surface literally draws heat from the leaf, thereby cooling it. "
Vapor Pressure Deficit - The Ultimate Guide - Dimlux Lighting - The Best Grow Lights
Simply put, Vapor Pressure Deficit measures the difference between the amount of drying power the atmosphere is exerting upon your plants. VPD is the key...
www.dimluxlighting.com
I take it that you did leaf temps . Or just guessing ."The plant’s experience is slightly different because they are usually a bit cooler than the room. If the plant temperature is exactly the same as the room temperature, then the plant and room Vapor Pressure Deficit levels are equivalent. But this is rarely the case! Usually, the leaves are between 3° and 5° F cooler than the room because they are transpiring. The evaporation on the leaf’s surface literally draws heat from the leaf, thereby cooling it. "
Vapor Pressure Deficit - The Ultimate Guide - Dimlux Lighting - The Best Grow Lights
Simply put, Vapor Pressure Deficit measures the difference between the amount of drying power the atmosphere is exerting upon your plants. VPD is the key...
Ed Rosestale
Member
Obviously all fans crispy and already stripped. Yours is not dutchpassion or whatever, yours is from dimluxlighting.com tailored to 5F LST difference, thats the reason why its odd. There is only one VPD chart, which is being used by other adding coloured borders for different phases or doing whatever changes and calculations, but the basic chart is the same for everybody. So your controler is closer to the true, but not completely since LST has not been taken into consideration.
secretmicrogrow420
Well-Known Member
you guys are over thinking this stuff lmfao ima stick with just checking my room temps and relative humidity during lights on / lights off if my rh and temps are okay im pretty sure the vpd is going too be okay lmfao. vpd sounds like a smart way of checking room temps and rh and converting that with some equation lmfao or am i missing something here?
PopAndSonGrows
Well-Known Member
The simple answer? --i wouldn't even worry about VPD until you've had several successful grows, and maybe getting to a point where your yield isn't gaining.
If you're just getting started growing, you shouldn't even need to look at a VPD chart right now
If you're just getting started growing, you shouldn't even need to look at a VPD chart right now
I agree as I was doing fine without it but I got this cool little controller that made me research what it is.... and trying to dial it in. Not extremely worried but I am really focusing on my next grow right now by learning on these plants what not to do lmaoooo ... but the more i can get right now the better for the next run. I know i probably wont even be able to smoke this shit and i'll just make brownies or something...
ALPHA.GanjaGuy
Well-Known Member
the original page that the chart came from www.dimluxlighting.com/knowledge/vapor-pressure-deficit-vpd-calculator/
if you fill in the boxes at the top of the page it will give you the VPD numbers, you can then scroll down to the chart, select your leaf temp offset (you check the temp of the leaf using an IR thermometer) and the chart will show the ranges depending on what stage of growth you are at
Phytoplankton
Well-Known Member
IMHO, VPD Is a bit overrated, particularly for a newer grower. While it’s certainly a factor, look at cannabis in the wild, VPD varies widely all day and night long. Keep your humidity between 40-70% in. Veg, 35-55 in flower keep the temps under 82-85 don’t need a chart. You’ll be fine.