NEED HELP WITH VPD!! MY LEAFE TEMPS ARE BASSACKWARDS!!

[MIMedGrower]

@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

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.

 

[MIMedGrower]

And would you guys defoiate I'm in about week 2 or 3 of flowering

I wouldnt take many leaves. There is a nice open structure with the thinner leaves and stretch. I would only cut stubborn overlapping leaves that keep staying wet.

Really looks good in there. :-)

 

[Aqua Man]

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 with co2. 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.

 

[Aqua Man]

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.

 

[MIMedGrower]

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.

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.

 

[MIMedGrower]

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.

Yes! Thats why i think focusing on it is not helpful.

 

[Aqua Man]

Yes! Thats why i think focusing on it is not helpful.

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.

 

[Aqua Man]

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

 

[Aqua Man]

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.

 

[MIMedGrower]

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

Well they used fans and foggers to change the temp and humidity. ;-)

 

[MIMedGrower]

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 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.

 

[Aqua Man]

Well they used fans and foggers to change the temp and humidity. ;-)

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.

 

[Rickypohiogrower32]

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.

Also important for seedlings I'd say .. knowing how to keep them in the correct moisture levels not to high or low

 

[Aqua Man]

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.

I absolutely agree with you here. Just like online charts should not be used.

But I will say standard parameters are VPD driven and inline with what VPD tries to accomplish.

It's just a fancy new term and calculations to be more precise. But I absolutely agree it's taken to far a lot of the time and to much emphasis out on being absolutely in the perfect zone. The thing I like about it is it gives number that make it easy for a grower... Much like a ph and ppm meter... Also I feel to many ppl just look at the numbers and get to overboard. Always read the plants those are all just guides. Each strain may like a little more or less of something. To many growers are not learning how to read plants and instead staring at numbers then when things go wrong they misdiagnose things because all they know are numbers and those numbers are nothing more than a guide and SHOULD be used as a guide NOT a rule.

 

[MIMedGrower]

Also important for seedlings I'd say .. knowing how to keep them in the correct moisture levels not to high or low

Eh i have grown great plants from seedlings in high and low humidity. Cannabis is very adaptable to conditions. Temp however has proven much more important.

So i try to keep my spaces 45% rh to 60% rh and 75-77 degrees farenheight lights on with a max 10 degree drop at night and 60%-65% max relative humidity to avoid mold. Also flow through ventilation and good air circulation 24/7.

has worked for many different strains and phenos with outstanding results.

I do agree that if i grew with co2 added and a hotter room with higher light intensity that these parameters may benefit from some dialing in. But everything happens faster as the light intensity goes up.

I also say manage the grow however we like. So many methods get us to the same place.