Questions about RH/Temp on VPD Chart

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Sh4kiNBabi3S

Sh4kiNBabi3S

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Hello everyone,

So I am running a 4ftx9ft tent with 3 Barney's farm Pineapple Chunk plants and it is currently in the middle of week 2 flower. I am running 1 spider farmer sf4000 and 2 spider farmer sf 2000. All of which are approx 24inch from canopy. I have mainlined and SCROG this grow. (Even though it didn't fill out as much as I wanted without a super long veg) I run the foxfarm dirty dozen @ 1/2 str every feed. And water with molasses on the water days in-between. Both Ph between 6.3-6.5. For ventilation I am running 1 AC Infinity 6inch exhaust with a 6inch air filter, as well as 1 6inch intake fan to supply new air into the tent. I also have 2 6inch round fans that are at soil level blowing air across the tops of the pots/right under canopy as well as 1 16inch oscillating fan that oscillates across the top of the canopy. My standard tent rh is only 40% during this season so I run a humidifier to bump up the RH. I also have a large dehumidifier for when it gets too high.

So my question is this. My grow tent is between 75-80° at most and I was viewing a VPD chart and notice that if your room is around 75-80°f then your rh should be around 70-75% to keep the VPD between 8-9. (From what I understand a VPD of 8-9 is ideal for cannabis) So with all the air circulation inside the room and the high rate of air exchange between tent and outside room, should I have an issue with PM or mold or anything? I read PM and mold thrive in temps around 68-72 and much above that and the spores don't propagate properly. So with that, plus the air circulation and exhange I don't think I should have an issue. I just wanted to run it by the people here who have much more experience than I in an attenpt to get some good advice.

Any information, either actual studies or anecdotal experiences with information about this would be really awesome!!

Also, I have attached some pictures for reference although I don't think pics will do much for this issue. However any other advice if anyone notices anything in the pics please let me know. Side note: The plants had a small nitrogen Def but it has since been corrected.( Hense the few lightly colored leaves on the bottom of the canopy.

And lastly, as for it not filling out the way I would have liked without a longer veg cycle. On my next run I plan to take 6 clones from the mother of these and allow each a 2ftx2ft area( 2deep x 3 wide) 4ftx6ft total, which will also allow room for the dehumidifier and humidifier inside the tent. While at the same time allowing me to top and keep a relatively short veg time of around 4-5 weeks to properly fill out. Does that sound about right?

Oh one more note. I obviously did abit of a lollipop pre-flower and intend to do another defoliation in 2 weeks when it will be 4 week flower to improve air penetration/circulation.

Really appreciate any advice anyone can give on this issue.

"Forgiveness is divine, but never pay full price for a late pizza."

-A Wise Man
 
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Nate_in_AK

Nate_in_AK

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Don't forget that your leaf temperatures will be lower than the ambient temperature in the tent. This chart assumes 5F degrees lower than room temp. So @ 75F, you would want to target 50% humidity. Coincidentally, this is my current environment. I see 75-80 during the day, and 72-70 at night. I've been keeping the humidity at 50% and things are going well so far.
 
Sh4kiNBabi3S

Sh4kiNBabi3S

10
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View attachment 1099589

Don't forget that your leaf temperatures will be lower than the ambient temperature in the tent. This chart assumes 5F degrees lower than room temp. So @ 75F, you would want to target 50% humidity. Coincidentally, this is my current environment. I see 75-80 during the day, and 72-70 at night. I've been keeping the humidity at 50% and things are going well so far.


Ah ok. So after checking the temp of the leaves using a lazer temp gun. I have found the leaf temp is 75° 80° and the room temp is 80°-85° F. So I want the RH @60-65% according to the chart. With the air circulation / exchange i should be ok with the PM or other mold. Assuming of course that I keep a clean grow tent and keep air circulation/exchange high right? I have just read ALOT about how RH above 60% has an increased chance for PM and whatnot. But with the VPD chart saying it should be around 60-65% bc of the temp, I just wanted to confirm that as long as I have good circulation and it doesnt get above 65% RH with temps of 85° F then I should be ok.


Thanks so much for the advise!



Thanks again,
 
Sh4kiNBabi3S

Sh4kiNBabi3S

10
3
Its Fox Farm ocean forest. However I had an issue with fungus nats bc I was using an old dirty closet for veg b4 I got a new veg tent. So I put down some natural playground sand ontop of the would, about 1/4 inch. It keeps the larva from being able to travel through the soil to get to the surface. The larva carapace get shredded by the sand very similar to how diatomaceous earth works.

Shout out to Mr.Growit's youtube channel. I don't remember the guest that had this solution, but it was a female and her advice was solid. Fungus gnats gonep prettymuch over night.

Can I ask why you were curious about the soil?
 
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boomgagem

boomgagem

Supporter
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Its Fox Farm ocean forest. However I had an issue with fungus nats bc I was using an old dirty closet for veg b4 I got a new veg tent. So I put down some natural playground sand ontop of the would, about 1/4 inch. It keeps the larva from being able to travel through the soil to get to the surface. The larva carapace get shredded by the sand very similar to how diatomaceous earth works.

Shout out to Mr.Growit's youtube channel. I don't remember the guest that had this solution, but it was a female and her advice was solid. Fungus gnats gonep prettymuch over night.

Can I ask why you were curious about the soil?

I use the dirty dozen as well and was wondering what media you were using with it. I’m using coco loco from foxfarm though. Just trying to dial my grow in a little better and you seem very knowledgeable. I don’t want to jack your thread though, lol
 
Sh4kiNBabi3S

Sh4kiNBabi3S

10
3
Oh your good buddy. Yea I am moving away from the FFOF and I am doing a super soil mix from here on in. For my next set I am doing 6 plants and for the base that I will use for my transplant from cube into the first small container. The base is just 2 cubic foot (4x 5gal pots) happy frog since it isn't has hot as FFOF mixed with 10 gal coco coir, 5 gal of pearlite and 5 gal earth worm castings. That should get me enough for the transplants + the 5 gal pots I will later move them into. Then once I take out the 6, 1/2 gal of soil/EA for the transplants I will add a 4-4-4 all purpose dry amendments to the remaining 30-35 gal ish of soil/coco/pearlite/worm casting mix and use the mix with the dry amendments when I transplant from 1/2 gal into 5 gal smartpots. Then I will just water with regular H2O ph @ 6.5 and re-amend by top sewing 4-4-4 or 2-8-4 every 3-4 weeks depending on light cycle. Add molasses during flower every other watering.

Don't get me wrong, I love the FF dirty dozen. It works great. I just also have some autos going with the photoperiods that are in my veg tent, plus the flower tent, AND my 2x4 that I use for my mothers. It just is ALOT of mixing different nutrients formulas with running basically 4 different feeding cycles. Its just too much, hense why I am switching to dry organic amendments to simplify things, and eliminate the need to flush the plants.
 
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Wh1teScorp1on

Wh1teScorp1on

390
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I’m loving Dutch Science line. They changed it recently and added a cal/Mag with Humates and fulvic acid. Each part is $50 lasts more than a grow. Usually have to drop a point of ph on mixing but that’s super easy. Had no lock out and minor tip burn by pushing the ceiling a bit but wanted to see how far I could go. If I told you you wouldn’t believe me.that’s running straight coco no flushing
 
Sh4kiNBabi3S

Sh4kiNBabi3S

10
3
I’m loving Dutch Science line. They changed it recently and added a cal/Mag with Humates and fulvic acid. Each part is $50 lasts more than a grow. Usually have to drop a point of ph on mixing but that’s super easy. Had no lock out and minor tip burn by pushing the ceiling a bit but wanted to see how far I could go. If I told you you wouldn’t believe me.that’s running straight coco no flushing
Yea it is my understanding that with any organic dry amendments you remove the need for flushing. However idk if 40$ for 1lb of dry amendments from the dutch science company is really worth it. That is way over the top. You can get a big 50lb bag of Down to Earth 4-4-4 dry amendments for $85-$100. ALWAYS look at the ingredients. 90% of the time you can save yourself ALOT of money by getting a cheaper 4-4-4 or 2-8-4 with the exact same ingredients as the more expensive stuff. More expensive does not always equal better nutrients.
 
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