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VPD advice
Cannabotixstarted grow question a year ago
I'm starting to now focus more on VPD now that I have a few more grows under my belt. I was wondering I'm in the seedling stage will running humidity around 70% to hit proper VPD be safe from mold or issues if I have great ventilation?
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gottagrowsometimeanswered grow question a year ago
Sorry I've to disagree.
VPD is related to the environment, vapor pressure deficit is the environment and how much vapour is in and pressuired tent.
LVPD is leaf vapour pressure deficit for this you need a laser temp. To check the temps of leafs.. the RH in the tent. There so much more to it than just that.
Id say to you. Focus on the 101sl.
Feeding management:
Ph control
Ec control
NPK values knowing when to change and dialing in feeds will take a few grow to get right if using self application nutrients daily
Marco/micro nutrients/enzymes/root stim if using soil. Cal/mag.
Importance of NPK and how these mobile nutrients work.
N IMPORTANCE, P directs energy, K controls the stomata vents. Understanding these are much more important than VPD.. keeping a steady RH FROM 65-75 DURING VEG. 50-65 during pre fower.
Past this stage if your RH is still high. Make sure you're using fans and great ventilation to prevent bud rot.
Also, DLI is much more important then VPD. Its possible its the most important thing to learn and get your head around as this will ensure you're giving the right amount of light in their respective stages. If your leafs droop when they go into darkness and are still droopy coming into lights on. Your stressing your plants out. Not enough DLI will cause slow growth, stretching and larf..
Learning what's female parts/male parts (hermies , nanners) learning bracts and how calyexs form bud will help you with this.
Really so much more to learn than vpd or LVPD leaf and vpd are to complete dif things. VPD is environment LVPD is leaf related. The amount of vapour absorbed/ the amount of liquid taken up. Rh control this + heat of environment
Terp1answered grow question a year ago
Den VPD in dieser Phase irgendwo zwischen 0.6 und 0.8 halten - sollte perfekt sein. Was bei einer RH von 70% einer Temperatur zwischen 20 und 22°C entspricht. 👌
Beim VPD ist es wichtig nicht NUR die Temperatur oder NUR die Luftfeuchtigkeit zu betrachten, sondern immer die Kombination aus Beiden.
Wenn du einen Parameter (zum Beispiel die Temperatur) nicht regeln kannst, dann musst die eben den anderen Parameter (Luftfeuchtigkeit) anpassen.
70% RH in der Keimling oder Veg-Phase stellen kein Problem dar, solange du alles Andere (Umluft, Bewässerung etc.) im Griff hast.
Keep Growing... Terp 💪😎
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Sit_Ubu_Sit_Good_Doganswered grow question a year ago
Leaf VPD = LSVP – (ASVP x RH/100)
feel any way you want.. that's what it is by definition, lol.
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Sit_Ubu_Sit_Good_Doganswered grow question a year ago
vpd is an equation of vapor pressure inside plant / just outside stomata.
if you have an infrared thermometer you'd want to take measurements of the leaves. The stomata are on the underside. Reference that with a VPD table.
23-26C @70% RH is .8ish to 1ish... depending on where you look you may see suggestions in this range or even a bit higher for early vege.
Without a solid source and suggestions you can be confident about, they can be a good ballpark. Measuring these things and keeping track of it helps. You can test out a particular vpd for several grows to build a baseline across various growth patterns and then try something new and compare. without a baseline it's like a chicken running around with its head cut off.
I don't take measurements at leaf, but my measurements are consistently made - i.e. probe is in the same spot, good circulation keeps climate consistent throughout tent. My vpd is lower than what i typically see on my phone app, but it's lower in a similar way each time. While i shouldn't suggest the VPDs i use, i can do the same trial and error as long as the offset (leaf vs air temps) remains consistent. you can subtract 3-5F if you want, but still not precise as an infrared taking leaf temp. The point is, it can still be useful even if you don't have the "exact" VPD.
I mostly just avoid problematic VPD -- too high/too low is bad. I've read you want no more than a 0.4 difference from dark/light cycles. I'd prefer the 'right' vpd with temps that keep me in 40-65% RH range... higher RH% for seedlinges is fine. The key there is it is short-term. Air out humidity domes religiously. 40-65% avoids higher risk of microbial growth. Should be able to stay within suggested VPD ranges for all phases and be within this range.
Google image search a vapor pressure deficit table -- take a peak at a few and see the range of suggestions just to get an idea. The better ones will color code it for too much and fungal/microbial risks.
avoid dew point. When you have higher RH and higher temps, when those lights go off the temps drop and RH can skyrocket. Look up dewpoint of your peak lights on temp/rh and make sure you don't get near it at lights out. If ever around 30+C/50-65%, you start seeing dewpoints that are easy to hit.
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