Discussion - Air movement - Oscillating fans vs Ingress/Express fans

[mostang64]

I've been researching and posting about nutrition recently, but it's easy for growers of all levels to get caught up tweaking their fertiliser ragimes and forget about other cardinal factors.

Adverse environmental conditions can ruin a grow! And this is why we take air movement and circulation seriously. Air exchange is critical for the control of temperature, humidity and gas exchange while movement of air is crucial to keep conditions optimal at the canopy level, ensuring plants so their best and pathogens stay at bay.

As a old school type of guy, I was never a fan of tents. They always seemed to be a pain to keep in check and my plants grew much better in a bedroom, with more area to work with. Bare in mind, I'm talking back in the days of supernova shades :)

Since having kids and getting old, I've had to scale my ops back and for the last 5 years, my only option has been a small tent. At first I tried to replicate what I did in larger spaces and whacked in a 400w HPS with a loud RVK fan and lots of oscillating fans. This kind of works albeit a bit of a faff to keep tweaking to compensate high temperatures. My plants would grow fine, but would almost always show signs of heat stress as they stretched.

Anyway, to the point of this post! After doing some reading around micro climates etc, it would seem that I may have been wrong to put in all those oscillating fans due to them being so close to the plants. When in a large area, you can position fans away from the growing area, but within a tent; they get in the way of the lights, take up growing space and sit next to the plants, blasting them with air.

Other options are to rely on passive intake or add a inline ingress fan. An inline ingress fan, placed at the bottom of the tent should draw fresh air in and push through the canopy on the way out. This reduces the space required and is a less aggressive approach, but is this enough to keep a dense canopy of cannabis flower within the acceptable range of humidity?

So, growmies, what is your opinion? Do you use oscillating fans, ingress inline fans or a hybrid approach? Or maybe you only rely on passive intake from negative pressure created from your extraction fans?

[2-Scoops]

I used to grow in a similar way to yourself years ago, I've never used tents, but i too scaled back into a cupboard which is run with a passive air inlet. I also run a small 6 inch oscillating fan blowing just set above canopy, now I've never suffered with bud rot growing in larger rooms even if rh was sky high you just cranked up big oscillating fans which worked a treat to prevent any nasties occurring.

But now im growing in my cupboard I've had bud bud rot once or twice on the odd bud here n their. So now to try to prevent it happening i have variac set to do temps and im investing in a small tower fan to stick on floor too. I here what your saying and have read leaves only need a small bit of rustling typo movement in air, but I've always found if rh is high blasting plenty of air movement around room creating a bigger leaf rustle really helps prevent bud rot and I've never found it being detrimental to the crop in any way what so ever doing that even, the bud is cock on.

I was always told when learning to grow if rh was too high to crank up those oscillating fans and its advice that I've always followed and its worked well for me so far. I mean what's downsides of lets say having a rh running 60 or 70% during the dark period in full bloom ? Is just theirs a risk of bud rot or summink else as well, i dont sweat on it personally speaking and crank up those fans im resigned to idea that some strains i may get odd bit of bud rot on odd bit of bud every once in a while, shit happens in my small space, i think certain strains can be prone to it no matter what rh is in the room if buds "nice and moist inside" (i love that phrase ) shit can happen no matter what.

Although reading about some things you would think twice about doing certain stuff, yet daft logic tells me it gets windy as fuck outdoors quite a lot and theirs some top shit grown in those very much so varying climate conditions. I suppose a lot of that is down to growers experiences of what you do and how you do things in your rooms. Point being theirs no need to take everything we read as written in stone when it comes to growing. Yes i suppose you will here peeps saying if you get things cock on following everything read bud will be best in world sorta thing, but my bud is best in world as is so no sweat.

[Dex]

Interesting topic I thought bud rot and root rot mainly hit sick plants... Lol I used to use 6 inch fan to blow at canopy but they are loud, so now I'm just using and have been using small desk fan the one that you plug in with USB :D

So far not bad and I always defol so not sure if that helps but I've never had root rot or bud rot not even mildew my tent which is what I've always used is nearly always got high humidity too N I've had some sick plants before led n now after few years of led.

I must just lucky on that department but not so lucky in keeping them alive with qb lmao I did fantastic with cobs

I'm interested on this topic so thanks for posting I look forward to the replies

[seymore_budz]

Interesting topic I thought bud rot and root rot mainly hit sick plants... Lol I used to use 6 inch fan to blow at canopy but they are loud, so now I'm just using and have been using small desk fan the one that you plug in with USB :D

So far not bad and I always defol so not sure if that helps but I've never had root rot or bud rot not even mildew my tent which is what I've always used is nearly always got high humidity too N I've had some sick plants before led n now after few years of led.

I must just lucky on that department but not so lucky in keeping them alive with qb lmao I did fantastic with cobs

I'm interested on this topic so thanks for posting I look forward to the replies

If you're in a small area then a small, USB fan would be more than enough to keep air moving through the canopy.

It's true that bud-rot will favor weaker plants. Also plants that have damage like tip burn or rust spots etc. But it will also attack healthy plants given the chance. If the RH is high within the canopy, little water droplets will form on leaves and within buds. Those conditions are ideal for the spores to germinate. Once they do, they bed into the plant tissue and pump out more spores, increasing chances of further outbreaks. This is why its important to remove moldy flowers quick-sharp.

It's a double edged sword I suppose. Plants may be happier without blasting them with air, but so with the mold spores.

[2-Scoops]

Plants may be happier without blasting them with air, but so with the mold spores.
Top

That's why i was always told to crank up the fans to prevent spores breeding yes.

How much water would a dehumidifier need to take out air daily to lower RH from 70% to 40% in a small grow 1100cm x 55cm x 230cm cubed room. A lot or not so much ? That's my question, i know it looks a tough question to me, i mean i think obvious answer would be 30% rh but what's that in amount (mls)

But you had my thinking on this one yesterday and even looking at dehumidifiers for a small area, you know £100 p- £150`ers. I'm gonna see how i go with this current grow cus last time i found a little rot i think was on this strain the last time i grew it out a few years or so back, although i do know this one is prone to bud rot cus duke had a similar problem till he cranked up fans. Anyhow lets see what cranking fans up does to help prevent it. In all honesty my plants have enough air movement with current fan but once that rooms crammed full its a different ball game for those spores if your not on ball. Tbh im not that worried on it and I've run with rh in bloom touching 70-80% in past without problems, which leads me to believe a lot of it can be strain related as well. But yes point being I've been looking at dehumidifiers

[Greenfingers]

have two 6inch fans on a timer to come on for 5 mins every 2 hrs and a 16inch fan thats on 24/7 that keeps the air around the pots moving.......