MIMedGrower
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@MIMedGrower here is one study. I realize this is not cannabis but I'm sure you will agree that it is in fact very relevant. Picking through in between work stuff if you want a few more just let me know. I would also state that IMO as plant growth is increased VPD plays a larger role. The more light, media providing faster growth (ie aeroponics etc.) co2. The more impact can been seen from VPD. This is first hand observations on my part. I haven't found or looked for any studies to back that up but I feel very strongly about it.
Vapour pressure deficit control in relation to water transport and water productivity in greenhouse tomato production during summer
Although atmospheric vapour pressure deficit (VPD) has been widely recognized as the evaporative driving force for water transport, the potential to reduce plant water consumption and improve water productivity by regulating VPD is highly uncertain. To ...www.ncbi.nlm.nih.gov
And would you guys defoiate I'm in about week 2 or 3 of flowering
I absolutely do. But again there are more variables at play also.Thanks man. I have read this recently. But it confirms what i said. They are using vpd to mitigate 95 farenheight temps or higher with low humidity.
The results are based on that high temp low humidity baseline.
This article does not relate to a controlled indoor grow in my opinion. The standard grow parameters would work as well. Seems the advantage to adjusting using vpd is mostly water conservation for a commercial greenhouse during summer.
For our purposes we can simply adjust watering to compensate for much smaller variations in temp.
Now i see why no advantage to adjusting humidity was found in temperature controlled indoor grows.
The plants get stressed enough for negative impact only at extreme environmental conditions. Which wont happen in my grow unless i have an equipment failure.
With your tightly controlled parameters you shouldnt see a difference with using vpd at all.
I absolutely do. But again there are more variables at play also.
Yes they are using VPD to reduce stress. It's very common knowledge around the scientific community that a KPA of 1.0 is a generally good target.
I think it absolutely shows VPD matters and I agree there is a lot more to it. Higher temps equals faster growth and temps up to 40c have shown this if using a good VPD. Without a proper VPD you cannot attain them. And thats the exact purpose of VPD is to reduce water stress... At any temp. You cannot attribute only temp or only humidity they work in tandem.
Like I said faster growth more important in my observation and that can be contributed by many factors.
VPD is not only related to indoor grows it's plants in general.
Like you say this was based on high temp low humidity which give a KPA value for VPD.
I have to disagree that it only benefits for water consumption. It clearly states the yield was drastically increased. So i would say there are several benefits.
Have to say my tightly controlled parameters are for VPD purposes. By reducing water stress we can improve stomatal opening and thus CO2 efficiency and overall photosynthesis and growth rates. This is also clearly stated in the study. It's all tied together. VPD by itself is useless.
Also @MIMedGrower if you look at the recommendation and growing conditions for VPD they mostly fall smack dab inline with VPD. I bet if you look at yours it will also be very close.
No need to focus on it if it's right to begin with. So yeah I agree with that point. I still however feel it is important to know and understand.Yes! Thats why i think focusing on it is not helpful.
But that's what VPD is... It was no longer to hot or dry once they incorporated VPD. The temp didn't change but the VPD did. So they used VPD to fix the issue.No bro. They said the growth was increased after they applied vpd to a too hot too dry greenhouse.
and they did say when its proper plants do best.
But what i am trying to get across is if you just keep your room in reasonable parameters none of this is needed at all.
Especially new growers should not worry about it. Unneeded stress and expense can result.
But that's what VPD is... It was no longer to hot or dry once they incorporated VPD. The temp didn't change but the VPD did. So they used VPD to fix the issue.
By reasonable parameters you mean reasonable VPD? Because that's what it is
Really VPD is a fancy term to to control water stress which has many negative effects on the plant including stomatal regulation which in turn directly affects CO2 assimilation, nutrient uptake and leaf temps among many others. It's a guideline and like most not a hard rule. Just like nutrient ppm etc
I also have to agree many take it as a hard rule and I agree with you that it's not. Also you can grow well out of the ideal guidelines and still be successful... Imo just not as successful as it could be.
Yes which further brought the KPA to a more favorable number. If you notice it's about the KPA. Temps can be adjusted indoors if you can and so should humidity if you can to give the most favorable KPA.Well they used fans and foggers to change the temp and humidity. ;-)
Also important for seedlings I'd say .. knowing how to keep them in the correct moisture levels not to high or lowThanks man. I have read this recently. But it confirms what i said. They are using vpd to mitigate 95 farenheight temps or higher with low humidity.
The results are based on that high temp low humidity baseline.
This article does not relate to a controlled indoor grow in my opinion. The standard grow parameters would work as well. Seems the advantage to adjusting using vpd is mostly water conservation for a commercial greenhouse during summer.
For our purposes we can simply adjust watering to compensate for much smaller variations in temp.
Now i see why no advantage to adjusting humidity was found in temperature controlled indoor grows.
The plants get stressed enough for negative impact only at extreme environmental conditions. Which wont happen in my grow unless i have an equipment failure.
With your tightly controlled parameters you shouldnt see a difference with using vpd at all.
I absolutely agree with you here. Just like online charts should not be used.Yes but growers on this and other forums are not explaining it that way and pretending other issues are being caused by it sonce they are so focused on it being so important.
And it is not too important to worry about unless your room or greenhouse is very hot and dry.
Honestly i think standard parameters are fine and for those learning to grow a much easier concept.
Also important for seedlings I'd say .. knowing how to keep them in the correct moisture levels not to high or low
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