Hi rh butt stupid or time to break some myths.

[Lost]

lots of air movement dries out your plants too much. JK

But if your humidity is 60% whats the harm? My area is 40% humidity (I know your stance on this), and its like walking into a windy day. How much do you think I am hurting my yields under your growing theory? I'm always down to increase yields..

 

[LordDankinstien]

Ok im not taking credit for this post at all!!! I found it somewhere else and the information is very usefull or at leaste it clears up some questions you might have. Im no expert at this so I wont be answering questions im just post this info as some brain food.



relative humidity is an expression of the actual water vapor pressure, expressed as a percentage of the maximum water vapor pressure possible under certain air+atmospheric pressure conditions.

@ room temp (~60*f), 100% humidity exerts a vapor pressure of 24 torr (~4.65 pound-force per sq "[24*{19.337*10^-3}]=4.65 psi pound-force). >24 torr of vapor pressure exerted on leaves, and leaves sense a vapor pressure deficit.

leaves stomata opening/closing influenced by difference between internal/external vapor pressure. opening/closing of stomata regulates gas exchange+transpiration, which in turn regulates growth/fruiting.

vapor pressure deficit is a lack of water pressure upon plant. this would be a low rh. it is indirect measure of water loss from plant. as plant attemps to balance internal/external vapor pressures, they draw up more water from roots and transpire it into the atmosphere. hence the de-humidifiers used in gardens.

air movement over plant+high temps+low rh reduce plants available water for sugar production. the roots uptake much more water during low rh. but all inter-related to ambient temp(avg. surrounding air temp), actual leaf temp, and root temp.

a 3'x3' plant can transpire a gal. during high vpd (low rh), or a cup during low vpd (high rh). vpd/rh measurements must take into account air temps.
generally, keeping rh as high as possible (~55-75%) keeps the plant in a comfort zone to its genetic desires. lowering rh provides a method of tailoring nute formulas, pushing parameters, etc - as they will be taking up much more water. keep in mind that the water uptake during low rh is mostly just that - water. keeping nute ppm/ec in balance w/ ph is good idea.

prevention of mold/diseases/condensation is the reason for decreasing rh, but it can be higher w/ air exchange/movement w/ tempered evaporation (air movement over/around plants). also, growth slows during high rh, but in fruiting, slow growth is not an issue, fruit production is. lower rh also increases translocation of calcium (why gardeners use calcium additives during fruiting - it is sent to every part of plant during increased water uptake via roots).

not having problems because the plants' comfort zone is pretty broad w/ comparable temps+air movement - just like there's a 'domain+range', so to speak, in nute levels, etc.

note: in general...
lower rh(high vpd)=increased transpiration, translocation, water uptake, greater calcium absorption/transport.

higher rh(low vpd)=slower transpiration, translocation, water uptake, slower evaporation, increased growth.

rh does not need to be >50%, it needs to be tailored to specific environment, w/ specific temps/air circ variables accounted for. can manipulate growth/water uptake from that comfort zone point (~45-65%, again, depending on gardens other inputs).

water uptake from roots+stomata opening/closing+transpiration are inversely related, but non-linear.
lowest water uptake prior to lights on. stomata closed @ night, partially closed @ mid-day (hottest) so as not to evaporate too much water.


Below is another post from the same person
stomata opening/closing is influenced by rh(vpd), temp(diff), light(spectrum(s)), hormones, etc. not isolated to rh influence. lot of science in this. discoveries in plant science/ag eng still continuing. basically, no variable can be read in isolation in garden environ.

most important time to influence/test/experiment on plants w/ different rh/higher night temps/etc. seems to be ~before sunrise/sunset, when the internal clock is most sensitive.

Hope you guys enjoy this I know it answered alot of questions I had.

 

[Jalisco Kid]

But if your humidity is 60% whats the harm? My area is 40% humidity (I know your stance on this), and its like walking into a windy day. How much do you think I am hurting my yields under your growing theory? I'm always down to increase yields..

You have been growing long enough to know there will be other cycles coming, so on the next one try it with less wind on the plants. Replace a few wall fans with some floor fans.
How can I put this.
yes you can run with no food in your stomach and half your mouth taped shut.You can do it every day until you die. But try it on a full stomach,your mouth wide open and see how fast you get there. Then using both methods and take a detour up a hill, look to see what happens under both circumstances. I sure one of them you will puke your guts out on the top while the other circumstance you just sweated a little more.
Just replace that hill with pm,rot,swinging pH etc. JK

 

[Jalisco Kid]

Ok im not taking credit for this post at all!!! I found it somewhere else and the information is very usefull or at leaste it clears up some questions you might have. Im no expert at this so I wont be answering questions im just post this info as some brain food.



relative humidity is an expression of the actual water vapor pressure, expressed as a percentage of the maximum water vapor pressure possible under certain air+atmospheric pressure conditions.

@ room temp (~60*f), 100% humidity exerts a vapor pressure of 24 torr (~4.65 pound-force per sq "[24*{19.337*10^-3}]=4.65 psi pound-force). >24 torr of vapor pressure exerted on leaves, and leaves sense a vapor pressure deficit.

leaves stomata opening/closing influenced by difference between internal/external vapor pressure. opening/closing of stomata regulates gas exchange+transpiration, which in turn regulates growth/fruiting.

vapor pressure deficit is a lack of water pressure upon plant. this would be a low rh. it is indirect measure of water loss from plant. as plant attemps to balance internal/external vapor pressures, they draw up more water from roots and transpire it into the atmosphere. hence the de-humidifiers used in gardens.

air movement over plant+high temps+low rh reduce plants available water for sugar production. the roots uptake much more water during low rh. but all inter-related to ambient temp(avg. surrounding air temp), actual leaf temp, and root temp.

a 3'x3' plant can transpire a gal. during high vpd (low rh), or a cup during low vpd (high rh). vpd/rh measurements must take into account air temps.
generally, keeping rh as high as possible (~55-75%) keeps the plant in a comfort zone to its genetic desires. lowering rh provides a method of tailoring nute formulas, pushing parameters, etc - as they will be taking up much more water. keep in mind that the water uptake during low rh is mostly just that - water. keeping nute ppm/ec in balance w/ ph is good idea.

prevention of mold/diseases/condensation is the reason for decreasing rh, but it can be higher w/ air exchange/movement w/ tempered evaporation (air movement over/around plants). also, growth slows during high rh, but in fruiting, slow growth is not an issue, fruit production is. lower rh also increases translocation of calcium (why gardeners use calcium additives during fruiting - it is sent to every part of plant during increased water uptake via roots).

not having problems because the plants' comfort zone is pretty broad w/ comparable temps+air movement - just like there's a 'domain+range', so to speak, in nute levels, etc.

note: in general...
lower rh(high vpd)=increased transpiration, translocation, water uptake, greater calcium absorption/transport.

higher rh(low vpd)=slower transpiration, translocation, water uptake, slower evaporation, increased growth.

rh does not need to be >50%, it needs to be tailored to specific environment, w/ specific temps/air circ variables accounted for. can manipulate growth/water uptake from that comfort zone point (~45-65%, again, depending on gardens other inputs).

water uptake from roots+stomata opening/closing+transpiration are inversely related, but non-linear.
lowest water uptake prior to lights on. stomata closed @ night, partially closed @ mid-day (hottest) so as not to evaporate too much water.


Below is another post from the same person
stomata opening/closing is influenced by rh(vpd), temp(diff), light(spectrum(s)), hormones, etc. not isolated to rh influence. lot of science in this. discoveries in plant science/ag eng still continuing. basically, no variable can be read in isolation in garden environ.

most important time to influence/test/experiment on plants w/ different rh/higher night temps/etc. seems to be ~before sunrise/sunset, when the internal clock is most sensitive.

Hope you guys enjoy this I know it answered alot of questions I had.

One thing this post does not mention is that when the plant pulls up the water(and some nutes it is not asking for) is that it changes the internal chemistry of the plant. Once the plant has hydrated it's self it then needs more down time to regulate itself and line up the carbs and protiens to get the enzymes up and running. It also plays with the pH in the leaf which is bad.

Yes you can grow nice green herb that does the job in getting you high growing most ways.But one thing I did learn from Krusty was the stress free theory of his. You want to grow trees with some weight to them you got to do what you gotta do. Suerte JK

Nice post by the way.

 

[Lost]

You have been growing long enough to know there will be other cycles coming, so on the next one try it with less wind on the plants. Replace a few wall fans with some floor fans.
How can I put this.
yes you can run with no food in your stomach and half your mouth taped shut.You can do it every day until you die. But try it on a full stomach,your mouth wide open and see how fast you get there. Then using both methods and take a detour up a hill, look to see what happens under both circumstances. I sure one of them you will puke your guts out on the top while the other circumstance you just sweated a little more.
Just replace that hill with pm,rot,swinging pH etc. JK

Interesting, i'll give it a try perhaps. Thanks for the input. Welcome back btw. :party0044:

 

[happyinmendo]

One thing about the opposite situation of bringing it down most people fail to realize is in the winter your rooms night time temps are pretty low generally. Anything under 65 degrees and most dehumidifiers are near useless and completely inefficient. They state such issues right on the box. The right kind of dehumidifier and a programable thermostat for night time heat is a huge bonus!

 

[REGISTRD]

^+2 Intresting,,,

Either way I need to buy a few more hydrofoggers so JK throw me your idea my cc is about to get FRIED>>Sell me a unit....lol

 

[happyinmendo]

The high humidity is never an issue... its the lack air flow to make it work symbiotically.

I've found while drying that no dehumidifiers even have to be used if you have a hurricane in the room of fans. Mold won't grow, BUT giving it a tiny little nook with no air flow and BAM there is some mold!

 

[Jalisco Kid]

I could not live where my dehuey would not work.Besides 2 rare days last year I do not think my room has gone below 62* and I run in the day. JK

 

[convex]

Thank you, convex and Jalisco.

You mentioned temps around 65F, is that inside the flowering room/area? Is that through flowering? I had days where it barely hit 60F, hardly ever hit 70F, and RH stayed really high (50% was the lowest RH I registered, it usually stayed between 65%-70%, occasionally getting higher). ...

Sorry Seamaiden, took a while for me to get back to this thread ;)
My ambient is 60-65 the lights bring me into the 70's.
This is with panda film for walls - I really think closing in your space will make a significant improvement.



Cheers

 

[Jalisco Kid]

how do u run high rh with out getting bud rot

I think it is what I spray my plants with and the constant air movement. That and I do not grow buds bigger then 5 inches anymore. I have a strain I made that goes big, Ms Walker, last time I grew it I had some fat buds(8") but I also had a few oz that were trashed due to grey mold.
JK

 

[Seamaiden]

Thank you convex!

Sorry Seamaiden, took a while for me to get back to this thread ;)
My ambient is 60-65 the lights bring me into the 70's.
This is with panda film for walls - I really think closing in your space will make a significant improvement.

Cheers

I had to bump this.

My husband, incredible person that he is, re-did the ceiling and insulation of my room this weekend. Dropped it about 2', added more of that 1" rigid stuff (I love that stuff). He also moved my ventilation fans and added a very nice baffle to keep light out but maximum airflow through.

I put in ONE 400W MH bulb, and after a little over an hour I had 80F with the ventilation turned off and no fans for movement.

OH HAPPY DAY! :banana: I'll laugh my ass off if I start having heat problems. I'm sure the RH will remain high because it's always on the high side down there.

Thank you convex!

 

[Shady]

JK I have been playing around with room conditions in my area, and since it is so dry (rh around 20-25%) I can see pretty immediate and drastic results in plants when I create fluctuations.

I started playing around more after reading an article on vapor pressure deficit (vpd) and all the corresponding factors (leaf temp, room temp, rh, etc) ... with that logic and finding an ideal range of transpiration is anything above 60-65% as effective as it can be? For that range IMO to not hinder the rest of the factors, room temp, leaf temp, air flow etc must be pretty ideal. No?

Currently I am trying to maintain around 55-60% rh with room temps in the 76-79 range. Don't think my temp gun is precise enough to check leaf temps, but things seem to be in range for ideal vpd....and results have been phenomenal compared to running the room without mods at 25-30% rh. Many of the micro diffiencies as well as PM (yes from a dry room with too much air flow) are falling back in place and getting in check.

Also with the raise in rh, you can more easily control higher temps in the room. My 81 degree room dropped to 78-79 when i added about 30% humidity. The 70% range will be too high for my room to keep things in check and ideal, but the high 50's low 60's seems to be ideal. I am sure now that its consistently in that range my yields will start to show great improvement...

I fully concur with the theory of Vapor Pressure Deficit... I've provided a few links to VPD studies in my journals... :cool

Since I grow trees we are talking about large surface area to be served by the root zone. Having a low rh will cause my girls to really suck up the liquids which throws my internal chemistry way out of wack. Once your leaf's pH is out it takes too much time to get it back to normal causing you to lose out on growth.
So I guess basically I sulfur burn,help my girls immune sys, use a lot of filtered air movement high volume low velocity(I use more floor fans then wall fans). I have been running a lot of stains lately looking for that perfect tree.So I guess it really is not the strains I normally run,had 13 different strains last run. Some friends believe it is the choice of strains I have,but that is not the case. I also do not let people in my room nor do I go in in street clothes. It also might be I am in southern socal so maybe there are not that many spores to deal with.
I just know 78*air,68*water,65-75%rh works with my girls. Higher air temps close my stomata,forcing too much water movement.Lower water temps would slow down the metabolism,higher too much fungus growth. Lower rh closes the stomata and higher my leaves feel funny(not scientific I know) I know Krusty ran above 80% but I feel it can be too much. JK

Sounds like you are in a good range for a fellow socal farmer... I run between 50 and 65 RH with temps that range from 78 to 85 deg. Lots of gentle airflow and no CO2 tanks in my small gardens, but no chiller on my res either which causes my water temps to stay at 76 deg with 24/7 airstones running... I wonder how the water temps in the res can help with nutrient uptake, pH, and VPD at the leaf's immediate vicinity? I'm also very interested in Sulfur burning, but running muliple perpetual gardens has prevented me from burning any... :itwasntme

 

[Venom818]

I think it is what I spray my plants with and the constant air movement. That and I do not grow buds bigger then 5 inches anymore. I have a strain I made that goes big, Ms Walker, last time I grew it I had some fat buds(8") but I also had a few oz that were trashed due to grey mold.
JK

gracias:passingjoint:

 

[Jalisco Kid]

gracias:passingjoint:

Ran into a thread of yours. Nice collection of girls you got and you seem to treat them well. I have been using just fulvic,light dose of kelp,cal 25,aminos,K silicate on my patients grows.there are about 6 grows I watch,with 2 cycles in they have not had pm when they did in the past. They also use 3 sulfur burns during a cycle. 2 of them included messenger with their sprays. JK

 

[Jalisco Kid]

Shady,it never occurred to me that perpetual grows can not use sulfur burns. Maybe you could rotate your plants so the mature girls are in one area. Then using the blue painters tape, tape of that area using a plastic sheet. You only burn 4 hrs during lights out. JK

 

[Shady]

Thx for the response JK! So does sulfur burning have a negative effect on buds and leaves past a certain point of bloom? I've also got carpet in my bedoom and wasn't sure if the sulfur would make everything smell like rotten eggs... :thinking

In my current Round 5 I have sprayed a couple times in the beginning of bloom with Dutch Master's Zone and Penetrator to prevent PM. I have also sprayed several times with BioNeem to control aphids and fungus gnats... Not sure how far into bloom it's safe for the BioNeem and if the Neem oils can clog stomatas...

 

[Jalisco Kid]

If you are not renting pull that carpet up. I would pull it up and buy new carpet for that room when I left if I was renting. I stop burning sulfur not later then week 3 and thats only if I have a pm waiting to come out on certain new cuts.
I do not know how good for prevention zone is but I use it to knockdown pm in patients grows. 35% peroxide works well also. I used to use it with a airbrush. JK

 

[greenblood]

humidity control strategy

long post:

source: BC Ministry of Agriculture, Fisheries and Food, June 1994, Floriculture Factsheet File No. 400-5

Understanding Humidity Control in Greenhouses

http://i45.invalid.com/i5rhvb.jpg

****

source: Argus Controls

http://www.arguscontrols.com/

VPD Application Note (PDF: 702 KB) - Full version of our paper on understanding and using VPD

VPD is a good indicator of plant stress brought about by either excessive transpiration (high VPD values) or the inability to transpire adequately (low VPD values). While plants are affected by changes in the surrounding air mass, they can also actively affect this same air mass. Whenever plants increase their own rate of transpiration a local decrease in the VPD will occur as the surrounding air absorbs this evaporated moisture.

There is also an associated cooling effect as the process of water evaporation absorbs a lot of heat. This cooling will further reduce the water holding capacity of the air mass and thus lower the VPD value.

[..]

VPD Does Not Measure Plant Water Use!

VPD can only tell you about the potential for water to evaporate from the leaves. There are several other factors that affect water transport including salinity in the rooting media, root health, and whether the leaf stomata are opened or closed. Although the actual rate of water loss is not directly proportional to VPD, there is a general relationship. It can tell you whether the crop is experiencing drying conditions and you can then make some assumptions based on this.

[..]

When the VPD is too low (humidity too high) plants are unable to evaporate enough water to enable the transport of minerals (such as calcium) to growing plant cells, even though the stomata may be fully open. Therefore, a VPD target threshold can be used to influence ventilation and/or heating equipment used to increase the VPD by reducing the air moisture level.

[..]

When the VPD is too high (humidity too low) the rate of evaporation from the leaves can exceed the supply of water into the roots. This in turn will cause the stomata to close, and photosynthesis to slow or stop. Once the stomata close, the leaves are at risk of high temperature injury since evaporative cooling is reduced due to the lack of water to evaporate

To avoid injury and death from wilting, many plant species will either curl their leaves or orient them downward in an attempt to expose less surface area to the sun. This can significantly downgrade the quality of potted and foliage plants and can also reduce the growth rate and quality of vegetable crops.

[..]

The ideal VPD range varies with the crop species and the stage of growth. The table below indicates VPD values in millibars at various temperatures and humidity levels. Although the values do not change, the interpretation of the numbers will vary for each crop species, the stage of growth, cultivation methods, crop acclimatization, and local conditions. We have arbitrarily selected the green shaded area (approximately 5.0 to 12.0 mb) as being ideal for an imaginary crop. The yellow areas indicate an acceptable but marginal VPD range and the red areas are either too high or too low. Again, you need to make your own interpretations for your crops.​

http://i50.invalid.com/j81lbo.jpg

 

[greenblood]

With that (above) being posted, I've in the last few weeks (since reading in the Krusty Bucket thread about 70% RH) trying a different strategy for the first time.

And that is not worrying about driving rh in the grow room down to the truly arbitrary number of 50%. Don't even ask where I got that. Maybe a FAQ along the way.

I don't have any elaborate controls in place, accept for an AC that keeps the temps below 83-84. The RH during the summer months is almost always 60-70 if left alone. In the winter I will probably explore humidification.