Led organic and purple

I forget his name but an LED engineer was on the stash podcast recently and he suspected people seeing cal and mag def with an LED over other lights was because they don’t have as many reds, so don’t put as much heat on the leaves

 

It’s low temps causing that with led lights. I just listened to the guys from hlg lighting explain it. Get your soil temp up to 75, and your leaf temp up to 78-80, and the P, Ca, and Mg can be taken up much easier.
Those are my ideal temps for led, just get em as close as you can. Everything you need is in the soil, the plant just can’t take it up as efficiently at cooler temps.
HTH
Cheers
Os

 

I usually run 6 different strains at a time, and there is quite a bit of variability between what strain likes what. Some do just fine cooler, some like it warmer. Bump the temps up a few degrees.
Cheers
Os

 

Hey thanks for that podcast, it was pretty good general information.
Link to that Podcast (Shane Torpey is his name):

In response to that suggestion in the podcast about mag/ cal deficiency, What I heard him say was that he didn’t know, plant nutrition was not his expertise. I’m going to call that questiopodcast suggestion a hypothesis, which was inconclusive. Several hypothesis were discussed as well. Plants sweat out P and K during high light (and heat ) during flowering under efficient LEDs (that’s MY hypothesis, and have read in the literature) and I can see purpling of stems in late flower. I would agree deficiencies are likely related to heat approaching the max recommended in an inside LED grow without Co2 (85 degrees).

 

I’m actually in a similar situation, and coming into fall temps are dropping, so I got a little heater in yesterday, 350w ceramic and just having it in yesterday and last night I noticed a big difference in growth. I did have to hang it though so it didn’t cook my soil.

 

I’m going to try and find the thread today. But a couple days ago I came across a thread in another forum that took infrared pictures using led and hps lights at two different temps. But for the LED to get the same optimal leaf temp as the HPS the air temp needed to be 84F. Which is what I’ve been shooting for now, seems good

 

Found the original article. Leaf Surface Temperature with HPS, MH, CFL and LED Grow Lights
I use that image in particular because i pretty much leave my lights at the ceiling

 

FTG,
That was a great article! Thanks for posting the link.
This may deserve a whole separate thread, but the. Again, it is relate to the OP’s question, sort of.

So, your post motivated me to find my IR No-Touch thermometer and measure the leaf temperature. It too is FLIR (Forward Looking Infra Red) it’s just not a camera. Results were that my leaves closest to the lights averaged about 73 degrees F (Leaf Surface Temperature or LST). Ambient in tent is 82 F. That means something huge, just not sure if it means my LST Can be up to 85F. Right now my fan run almost constantly to keep the tent below 85F. I could set my fans to come on at maybe 90 F. What is optimal LST???

5x5 Tent
AC Infinity 6” with beta controller
12” oscillating canopy fan slow speed
HLG 600 R @ 550 wall watts @ 36” from canopy
Tent Ambient = 82 to 83 F
Microlife USA Inc. NC200; surface mode (Amazon.com)
Top LST 71 to 75 F ……….. 10 degrees lower

I have been trying to keep my max air temp below 85. Wonder if we should be measuring the LST for that maximum instead. I didn’t have time to read a hefty sci article this afternoon.

Thanks again for the post, and the idea. Start a dedicated thread?

 

Yea we are kind of hijacking OPs thread here haha
It’s great you can actually check your LST so yea I would definitely experiment with 90F. In my case I’m noticing a big diff just from touch of LST by having a little 350w ceramic heater in the tent. Don’t have an IR cam so I’m just going off look and touch.
If I remember correctly from the article 88F was the ideal LST

 

Just use an IR thermometer that does surface temperature. Here is the exact one I just used:
$24 bucks… or borrow one

 

I use cob leds and have a FLIR thermal imager. I typically have a leaf temp at least 2 degrees lower than air. I blow hot air down from the ceiling in my room and over the heat sinks to help warm things up in the winter.
With hps lights, the infrared energy is absorbed by the leaf surface temp and is often 5-7 degrees warmer than air temp. Distance and fans make every set up a little different, but you get the idea. Warmer air temps are a must. Soil temp is often cooler under leds as well. Cold soil has the same detrimental effect as cool air temp. Nutrient balance falls out of ideal. Things like Mg, Ca, and K whose uptake is reduced by low temp, appear in deficiency, while uptake of nutrients that are less effected by temp may appear to burn the plant.
Cheers
Os

 

That’s a good grow hack if ya have one.
The “gun and red dot”, infrared thermometers have gotten inexpensive. Lowe’s or HD, $20 for a cheap one that works really well. That’s what most folks are using for leaf temp.
Cheers
Os

 

What you want to try to bring your leaf temps up is set up your tent this way. Passive Intake air from the top and pull air out the bottom with your fan. That will allow you scavenge heat from the led by pulling air down past the heat sink on the light and warm up your leaves. Makes a big difference. You should be able to dial it in pretty sweet with the fan controller. Start at a low speed and watch your leaf temps. There will be a point in the middle of the speed range that pulls down the most heat, without adding too much cool air from outside the tent.
Cheers
Os

 

With an ambient tent temperature of 83 degrees, what would you say would be the optimum leaf temperature?
I keep reading that max air temp is 85. Comments?

BTW, the papers that the Blackdog LED site recommended of their white paper were not hardly applicable (waste of time, growing in shade).

 

I like leaf temp 78’F -80F. I prefer 78’F, cause it’s easier to manage vpd at that temp. The actual air temp doesn’t really matter, it’s all about the leaf temp.
Cheers
Os