Trouble adjusting to COBs

boostedhonda said:

Kind LEDs are supposed to have IR also but there is a video on YouTube where htg supply compares their max uv fluorescent to the Kind led in a test for uv and the kind did not register any uv. So although there may be some uv light emitted I don’t think it’s enough to raise the leaf surface temp like say an hps would. I try to stick in the 80-85 range when possible and the respond well

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UV is not IR in fact its at the complete opposite end of the spectrum

Clearly I was too stoned when I wrote that

Randomblame said:

How much watts per sft.? It sound like too much intensity also known as bleaching.
Is the yellowing on the upper leaves and the leaves below the canopy stay intact?
At which current the COB's are driven?
How much distance between COB's and canopy?
Way too less info for an adequat answer, mate.
Dimm the light further or rise the whole lamp a few inches. Reduce the light below 30.000lx until they recover, than rise it slowly to 50klx, not more! Temps should be at least 25°, better 28°C, 18°C at night in okay. Plants should use the same amount of water as with HPS.
Maybe you should consider switching to a hydrosystem. Coco drain-to-waste systems work very well with LEDs, as the plants in a hydro system can uptake more nutrients.
Plants under LED have much more nutrient requirements.. It's not only cal/mag.

If the overexposed leaves are already starting to wither (upper half of the plant is yellow), forget them and put on a few new gals. Watch out for 16-24" spacing next time and slowly increase the intensity but not more than the plants can handle.
Remember, 60klx is about 900μmol/s/m² (a bit less), which is close to the maximum without additional CO². Have had the same issues with soil using 400w of COB's in a 2x 4' tent 12" above the canopy and dimming to 320w helps a lot.
For plants in soil I recommend 500-700μMol/s, in soilless media up to 900μMol/s without CO². Above a certain intensity it's difficult to feed the plants adequately, especially in soil. Vermi- and ripe garden-compost provide a large amount of nutrients over a long time and liven up the soil with beneficial microorganisms, which are neccessary. You can add both to your soil without letting it ripen for a long time, it's imo only needed if you add powdered bio-fertilizers like blood- or bone-meal, which need soil living bacteria to make it usable for the plants.

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I have 49w per sq.ft., which I know is a lot but at 40cm from the canopy it's about 50klux all around the room. The hps also had about 50lux right beneath it but dropped off to aroind 15 in the corners.
BUT it doesn't look like bleaching and the lowest leaves are affected the hardest. New growth actually is doing good!
I dimmed down the lights a good 20% or so (I no longer have the lux meter). I do have phone app to measure the lux but those values are clearly higher and unreliable, only usable to compare dimmerent heights/dimms to eachother.
Maybe they really do need more food? I guess I could give like half of them more and compare the results

50w/sft is too strong in my eyes, that's probably over 1000μmol/s/m².
Lux is green weighted, which means its optimized to human eyes, you can not fair compare HPS Lux vs LED Lux.
Dimm the light to 30-35w/ft²(efficient way) or increase the distance to at least ~24"/60cm or more(inefficient way). Yellowing from below means not enough nutrients, probably not enough N. Plants under LED have higher nutrient requirements, as mentioned a few times.
If a plant gets too little nitrogen at the beginning of its life, it will start to turn yellow early in flowering. You can then no longer supplement the missing nitrogen to avoid this effect. Give a good handful of horn shavings, preferably in different grinding stages to your substrate. Then let the soil ripen for at least a couple of weeks. Canna has also a mono line, that is, you can N, P, K, E, Mg, Ca, Tracemix, ... also buy separately and increase specific nutrients. Especially if you use such a strong light, consider switching to Coco or DWC.
Have a look at these thread! He use dwc systems with great success and never ever need 50w/sft.

https://www.rollitup.org/t/dhp-presents-citizen-cob-1812-3500k-80cri-vs-1812-3500k-90-cri.932990/

Trust me 50w/sft is wasted energy and the higher the intense the difficult is it to keep your plants healthy.
It's simply to much goodness, mate!

Strange that some folks have problems and some don't.
I imagine if a problem exists then higher light levels will only compound the issue.

We all have different set ups. It seems a lot of folks add Cal/Mag but not everyone and some folks add it and it doesn't help.

Maybe everyone should list the following info to try and spot the constant in the set ups that are having issues.

Light intensity, w/sft (assuming were all using relatively efficient Cobs)
E.C
Air temp
Root temp

I'm wondering if we might see a difference in root zone temps for those who previously used HPS, maybe folks growing with a cold zone, like a ground floor level grow or a basement grow or on a concreate floor ect. I grow on the top floor and my house is living temperature, the floor has heating pipes which probably help keep my root zone from dropping too low.
Lets say you grow with HPS and you have a cold zone under the floor, you might not notice an issue because the radiant heat of the HPS would help keep the roots warmer, you change to LED and suddenly have almost no radiant heat, all you have left to keep root zone in check is your air temps, which you raise because many people told you higher air temps are needed. But at lights off your air temp drops and your cold zone drops your roots that few degrees lower than you would like. Your lights come back on and again all you have is air temp to raise that root zone temp, that might take hours, the result is the reduction in magnesium uptake because the roots are too cold.

Like I said earlier in the thread, I don't have deficiencies and I don't add cal/mag, but my tap water is hard. So why don't I have the same problems, I'm not some super skilled grower, so perhaps its literally the fact I grow in a room on the third floor and the fact my veg tent vents into my flower tent at lights off, both things keeping my roots that few degrees warmer than you guys that are having problems.

Sorry for waffling, just woke up and need more coffee.