steamroller
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I ignore vpd chart especially in late flower. I shoot the main cola and try to keep it under 80f @ 45%So basically I understand VPD and manage it well .
Now at week 6 almost budding I have a question .
While I can manage to keep leaf temps and RH in line the temp of my buds is not inline with leaves .
Does the bud count or should surface temp be taken only on leaves ?
My buds are close to matching room temp, maybe 1 degree lower thanks to fans . This must be due to mass compared to a leaf ?
I am not having problems since RH is 40% but I just wonder if there is more to VPD in regards to budding .
After making the thread I thought maybe it only applies to leaves ?tVPD is calculated at the leaf, not the bud. That said, you need to obviously look at the whole. You can burn your colas if you ignore them and just measure the leaves.
It's a balancing act that you just have to get experience with to ignore VPD and use your senses instead.
Not sure how else you'd measure LST if you wanted to calculate VPD. That said, you'll get fairly good at guessing leaf temperature.Like one of those $12 jobs? I have one of those...
But still, that can't be the way plant temps have been measured for all the advice of the past.
I used to be sure, but now I'm not! My method used to be to hang a temp/rh probe an inch or two above the canopy and use that as my measure.Not sure how else you'd measure LST if you wanted to calculate VPD. That said, you'll get fairly good at guessing leaf temperature.
Vapor Pressure Deficit indicates the difference between the internals of the leaf and the external environment. If VPD is very high, transpiration rates increase which drives water uptake. If nutrient solution (assuming hydro) flows into the plant at an increased rate, it can cause nute burn. The inverse is true, as well. VPD is also a cooling mechanism for plants.It’s leaves because that’s where the majority of stomata are. VPD directly interacts with stomata opening and closing thereby setting respiration
Have you checked for fox tailing?How are you measuring bud temp? How are we supposed to measure crop temp anyway? I'm hanging an AC-Infinity probe just barely over the canopy. An inch higher is a lot different, as is an inch lower.
I have thermometers at various parts of the tent. Under the canopy is 73-77F all the time, and RH ranges from 33 to 45. In the canopy is about the same temp, higher humidity. at 53-55% Just above the canopy, temp is 80-81F, and RH is 48-50%.
I'm 6 weeks into bud now, and due to inadequate space, I have about 1300 PAR in the center and 400-500 at the edges. The temps and RH are pretty stable since I added a power input fan running 24x7. I'm surprised, but the leaves right under the brightest area don't seem to be suffering.
If your environment is stable and your plants are healthy, my bet is that you can guess LST within +/- 1F, at least that's been my experience. That's not saying i don't check with a IR thermometer, it's easy enough. Even if your LST offset moves a bit, it only moves your RH sweet spot a tiny bit and your instruments measuring temps/RH and controlling temps/RH are only so accurate anyway."I'll take definition of 'leaf surface temperature' for $500"
Gotta agree with you on the first part and there's nothing stopping a grower from guessing any of the parameters of the grow environment. Or all of them for that matter, right? One of the reasons to use a metric like Vapor Pressure Deficit is to remove or reduce the inaccuracies and unknowns. Right now, I've got Gorilla Glue autos seedlings and the LST offset has ranged from +2 to +4 over the past week. There's no way that I could accurately guess the values - humans suck at things like that. Since it only costs $20 for an IR thermometer, why would I not just spent the $20 and remove all doubt?
Techniques evolve over time as technology improves. Just my opinion.Like one of those $12 jobs? I have one of those...
But still, that can't be the way plant temps have been measured for all the advice of the past.
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