AF lighting cycling and heat

[budconnoisseur]

Right now I'm a couple weeks in to my first Autoflower and first indoor grow, with that there's been a pretty big learning curve. Currently i'm running a 18/6 light cycle with the dark period starting at 10pm and finishing at 4am. I've been monitoring the temperature and have been a bit concerned with the temps, at around midday the box is sitting at 32c/89f and drops to around 23c/74f in the dark period. The last few days however it's hit heights of 35c/95f and that's where I'm drawing the line, I've tried lots of different things including temporary fixes like putting blocks of ice in the box and nothing has significantly lowered the temps. So my goal is to move the light cycle 1 hour per day so that the off period is between 9am and 3pm ( the hottest part of the day). My question is, does anyone see a problem with this? is moving the light cycle in 1 hour increments likely to stress the plant? Also how dark does it need to be in the off cycle? Being the middle of the day and the environment i'm dealing with it's likely there will be a lot of light leak and although I realise AF can be run 24/0 there seems to be a lot of controversy about light leaks hermying a plant if you do choose to have a dark period.

p.s I will also mention that this isn't really a case of bad circulation or outflow, light is only increasing outside temp by about 3-5 degrees.

Thanks for any advice

[Ozzy420]

Most flowering cycles are 12 hours on 12 hours off.

 

And a lot of people will run there light at night at the cooler times to help in keeping temps low.

 

Through out the day if lights on better air flow or you could use aircon...

[Ford Fairlane]

are you seeing signs of heat stress? putting ice in the res is a great idea, but you won't see any change the air temp. plants outside routinely see temps in the mid 30's and higher without too much issue, as the roots stay fairly cool undergound.

light leaks should not effect auto flowering plants.

If you are not seeing issues regarding heat, then don't worry about it. best not to muck about much with auto's or any plant once in flower imo. But you are right, many people do run lights through the night to help control heat.

Do you run a cooltube or vented hood? may be the answer for next time..

[Sir PsychoHashy]

Being auto's you don't need to worry too much about light cycle interruptions, just leave the lights going at the end of your current cycle so that the next dark period occurs during the following day and they will be fine.  I run my light cycles to be on at night and off during the day for heat reasons, only downside is that having lower temps during the dark period is preferable for bud development, but on balance in my hotter climate it works out better doing it my way.

 

As for heat, higher air exchange will help, and making sure you aren't running too high a wattage for the space you are growing in can be a big one as well,  Can't really advise on those things with the info you have provided.

 

Temps like that are not ideal, but as Ford said, if the plants aren't showing signs of heat stress, don't stress about it.  I've had one strain basically die from it this summer, and others affected in varying degrees, so some can deal with it much better than others, and my temp issues were higher than that at the time.

[budconnoisseur]

Being auto's you don't need to worry too much about light cycle interruptions, just leave the lights going at the end of your current cycle so that the next dark period occurs during the following day and they will be fine.  I run my light cycles to be on at night and off during the day for heat reasons, only downside is that having lower temps during the dark period is preferable for bud development, but on balance in my hotter climate it works out better doing it my way.

 

As for heat, higher air exchange will help, and making sure you aren't running too high a wattage for the space you are growing in can be a big one as well,  Can't really advise on those things with the info you have provided.

 

Temps like that are not ideal, but as Ford said, if the plants aren't showing signs of heat stress, don't stress about it.  I've had one strain basically die from it this summer, and others affected in varying degrees, so some can deal with it much better than others, and my temp issues were higher than that at the time.

I would have thought it would have been better to move the light schedule in increments rather than all at once..?

[budconnoisseur]

I moved the grow box today into a cooler room and seems to be staying around 30 degrees now. I attached a couple pictures of the setup and plants. Running 600W HPS at 15" high. The bigger plant is in its 3rd week and the smaller plant is in its 2nd. Bottom leaves are yellowing and burning on the bigger plant and leaves are curling on the smaller plant. Am I right in thinking nitrogen deficiency?

[Sir PsychoHashy]

I would have thought it would have been better to move the light schedule in increments rather than all at once..?

 

Nah, it's fine, especially with auto's as they aren't photoperiod sensitive.  But even with photoperiod plants you can do it all at once so long as you extend the dark period rather than shorten it as it's the 12hrs plus of dark that triggers the flowering hormones.

 

Can't tell colours on HPS pics, but those plants look fine except for maybe a little heat stressed.

 

You want to deal with temp issues in that little grow box, biggest thing to do is drop the wattage, the heat output of a 600w HPS in that space is too much to effectively draw out of it, even if you use a vented cooltube.  400w in a cooltube, not a problem, but even in winter I can't get away with turning mine up to 600 in a vaguely similar space.  Either that, or make a bigger grow room, 1.2*1.2*2.0 is a good size for 600w.

[wietlover]

 You want to deal with temp issues in that little grow box, biggest thing to do is drop the wattage, the heat output of a 600w HPS in that space is too much to effectively draw out of it, even if you use a vented cooltube.  400w in a cooltube, not a problem, but even in winter I can't get away with turning mine up to 600 in a vaguely similar space.  Either that, or make a bigger grow room, 1.2*1.2*2.0 is a good size for 600w.

+1 on that ... 600w is far to much for that little area ..... Even a 400w is gonna give you heat problems .. A 250w HPS would be a much better fit for that size grow area.

[budconnoisseur]

Hey guys, 

I've gotten the heat down to a much better range, seems to be sitting in the 24-30 degree range. However one of the thc bombs is feeling a little sick and I can't figure out why... 

Started LST earlier this week and is in its second week of flowering. Soil and perlite mix and feeding with a light dose (15ml/ 9 L)  of Seasol Powerfeed for Tomato's and Vegetables ( the red one). Also just started giving it seaweed and blood and bone (hoping that it would solve some of the easier deficiency problems). The other thc bomb which was planted a week later has no issues and is looking healthy with the same treatment. Only other thing I can think of is a phosphorus deficiency and unfortunately don't have a PH tester right now.  Any suggestions as to what it could be? cheers