LED feed demands

It seems that changing to LED, highlights deficiencies that we couldn't see before. That little thing, that would of made things better, but we couldn't see it before. However, this is just an opinion. Not shared by everybody.

The most common issues we see experienced growers having, before LED's, is Calcium and Magnesium. Due to softer water supplies combined with feeds that expected it to be harder. So it follows, that many of us were close to seeing such signs, but it's switching to a greater level of illumination that highlights it.

I think I'm seeing a few people switch to LED's and isolate that individual thing that was always holding them back, but never really showed itself. Then, rectifying the situation, by adding that thing to balance up their feed, and then increasing everything by perhaps 25%.


I'm here, as I'm interested in seeing a few peoples stories.

My story starts with me using flower food, from cuttings through to bud. But with Nitric acid in grow, and enough of it to actually raise the N level to that of a well known grow feed, Canna. I did this for some time. Then moved to LED's and saw a N deficiency. Which is really what you would expect. Now, I have to use grow food, and Nitric. The P acid won't do. On top of which, I have had to move my EC up from 13-14 to 16-17. Which is a huge shift in N usage. If I lower my feed, I still see the same signs I used to. N deficiency and a light chevron effect to my leaves. So I know I'm only feeding so high, to accommodate these.


So, I had to increase the N in my nutrient profile, then stick 20-25% more nutrient in.

What steps have other people taken, to ensure the correct feeding regime after switching to LED's ?

LED's rev up the metabolism of the plant. Most people just bump up the bases or cal-mag. I had to add epsom salt to Jack's 3-2.

yeah that right as LED producer i can tell you that you needs much more [FONT=Arial, Helvetica, sans-serif]cal/mag as with HPS. the plant can used much more affective with Led as HPS
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I use maxibloom and changed my lighting to led. Chemdog wanted more mag but everything else seems the same. Stems get purple where they are lit though. The backsides are green .

As a soil grower, I'm seeing this in my current grows.

My soil bed started off beautiful then 4 weeks into flower went to shit. But only one set of plants. The other 6 look great in comparison but you can still see there are some deficiencies.

I'm going to be harvesting soon and getting a soil test done. I'll need to find a way to increase the calcium and the magnesium, as well as add a long release Nitrogen source. And possibly a long release Phosphorus.

Growing under HPS was easier, but I believe you are correct, f-e. There is definitely a learning curve to LED and minor issues that you never really saw under HID are amplified by the plants efficient use the light provided by the LEDs.

I feel like such a newb growing under these things. 5 crops in and I'm still playing catch up. I think I'm finally on the right path though. Next couple of crops will tell the tale, because this current one is a lose in my book.

I like what you said here

So it follows, that many of us were close to seeing such signs, but it's switching to a greater level of illumination that highlights it.

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When the HID is too close, it's obvious, because the leaves are in distress due to the heat. Also your hand feels it. When LED is too close, heat is often not an issue but the light intensity causes problems which creep up slowly instead of suddenly like with HID. I think that is a big thing. It has people wondering what is going on with my plant?! did I feed them incorrectly.
IMO HPS has this foolproof feature where you can't really lower it without getting heat damage, resulting in a nice PPFD for growth. With the leds you can go bananas.
Most HPS systems go from about 1000par in the hotspot to 500 at the edge @ normal hanging heights. Some leds these days are trying to push 1000 and higher everywhere.

I dunno, I'm just not a big believer that the light causes problems in the plant. I never heard of CMH or CFL or T5 deficiency either. All of those lights are different. Maybe the light causes/requires a different environment, sure. but then it is an environmental problem. For instance we know that the calcium uptake is dependent very much on transpiration. I think HID just increases transpiration with heat/infrared. I can't really match the transpiration of CMH without making the room quite warm. You have to have the right leaf surface temperatures for it. Maybe cannabis likes really hot jungle leaves. Orchids do better when they have colder leaves compared to warmer leaves with the same light intensity.

I use CMH and LED (COB, mid-power and purple in the past), alone and together. I have had what people would describe as "led deficiency" but in my opinion it's because the light was too close (or
the plant got too tall, haha). I measure the light intensity so I don't really go by hanging heights. When my light levels and environment are good I just don't have any of those 'led problems' people talk about. Recommend at least a lux meter to all. Just use conversion factor for lux→par and all your questions are gone... within a 10% margin of error. More than good enough.

Well, I'm not saying thats the end of it. I can only post my own experience and thoughts.
If your grow system/inputs/methods are bordering on lacking calcium maybe the led can exaggerate that problem, coming from a poorer hps spectrum. Different pigments (beside chlorophyll a&b) surely respond to different bands of light... I would have to experience it myself to believe in it.

Thank you people. It's been illuminating

I'm really starting to believe that 400w of LED can equal 600w of HPS. As long as it's recent LED's from top manufacturers. Not a totally unknown purple ufo.

Very interesting !
I agree that the LED burn creeps up slowly .... it took me awhile to understand it....
Im in the same boat too, im running 4 King Spectrum 602 with Co2 at 1500 ppm and all the sativa leaning hybrids at the 3rd week are starting to show severe deficiency all over....

They all are in organic recycled soil with a nice lime pack of gypsum , calcium carbonate and dolomite but they look always hungry...

Mainly N but also P

I kept the more sensitive strains little far than what the manufacturer raccomends but some still look weird....im starting to think that some weak genetics just don't like that insane amount of light.....

Had same issues since my first led grow, indeed there was a need for more cal/mag overall but from what I’ve seen since I hold my mothers under LED the clones acting more and more normal from em, compared to clones taken from „non-led“ mothers, same with genetic never been breed under „non-led“ lights...

Great thread!

Add red?
I had the thought to hook up my 1750 Veros.
It went away.
But then I was wearing mismatched socks as well so I’m not sure what it was.
it didn’t seem to hurt the plants.

Keep in mind the largest variable in this question, and that's which spectrum are we talking about. There are soooo many different LED offerings now, and even custom built spectrums as well.

Is there any specific spectrum which can be considered "LED light" these days?

Yes, leds helped me dial in my organic soil recipe and add-ons much better. Once you figure it out it's smooth.

Douglas.Curtis said:

Keep in mind the largest variable in this question, and that's which spectrum are we talking about. There are soooo many different LED offerings now, and even custom built spectrums as well.

Is there any specific spectrum which can be considered "LED light" these days?

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Sure, I think you can make some generalizations about the phosphor coated leds (white leds). they all have a pretty similar spectrum. (dont quote me on this in 2020 or 2021 - things are changing quickly)

(edit: the picture doesn't work, try clicking this text. these are 90CRI so they are different than the more typical 80CRI but the idea is about the same)

The spike in the blue (about 455nm) is beause it's actually a blue led covered with phosphor. So a lot of blue makes its way through. Then there is that 480nm valley. Higher CCT have a bit more 500-580nm. Those are some characteristics.

I guess this image shows the difference in the red range between high and low CCT better


But then why would the plant do worse with a spectrum that is objectively richer (than HPS)? You'd figure it would express itself better, instead. Shouldn't the sun do the supposed "led deficiency" thing, but then 10 times harder? The sun is like a nuclear combination of all light sources we ever made, on crack. I have a bottle of calcium nitrate here, it says on the label that you should consider adding it in cases of low transpiration. I still think it's down to low leaf surface temperature + intense light causing too little trasnpiration and some kind of shit going on where the new growth isn't getting enough of what it needs.

I hate purple leds but I've grown top quality under it... 0.7 gpw and small buds... still it was some of my most praised ever (the best rated comes from the CMH-only). Anyway, if even those purple leds allow the plant enough light quality to do what it needs to do with the calcium and boron and whatever to become DANK, then I just find it hard to jive with this whole spectrum/nutrient thing.

I don't mean to preach and be repetitive of course. it's just that if I dont have those problems, I dont want other people with the same hobby to have them either. Or maybe I am just lucky, who knows. I have grown lots of crap bud, truly worthless weed that I would be ashamed to share, hehe. But it still came from healthy plants! I measure the light intensity and the leaf surface temperature. Those things alone will put you miles ahead of where you were before. Just my 2 cents


By the way, here is a picture from a drama that occurred somewhere in LED Land:

Truth or fiction? Who knows... long story I guess

Just perhaps, having all that light, without the IR content, is driving feed requirements that are not being met through transpiration.

A hydro plant in a greenhouse see's many levels of illumination during the day, but often just one EC, or perhaps a day and night EC, where the night time feed is stronger. In the day, when the sun is strong, so is the IR content, opening the stomata. When the light is weak, so is the IR content, slowing transpiration. I'm no biologist, but plants have evolved with whatever is at the root, being what they have regardless of light levels. Perhaps there is a response to IR light, beyond just the temperature. A regulatory mechanism that LED's don't influence.


Warming up the room seems to be a common theme to make leds work. I have found a couple more degree's a good thing, and the high temperatures of summer caused no issue. Heading into Autumn I'm actually planning extra measures against the cold. One chap actually extracts from the floor now, bringing in air up top. In an effort to bring down heat from the lights. I mean.. wtf

If you join the dots, a picture can be made where IR is the main culprit. Or, a picture of a penis. It depends what you want to see at this point.

My plant is growing in an EC of 1.7 or 1200ppm in early growth under 2 batten fix LED lights (20W each) I bought from Stratco and is not showing any signs of nute burn, it is loving it.

exploziv said:

Yes, leds helped me dial in my organic soil recipe and add-ons much better. Once you figure it out it's smooth.

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I'm still working on getting mine dialed in. A soil test should help immensely. My biggest challenge will be trying to determine what to use for long release amendments for heavy feeders. This last grow in my new tent kind of kicked my ass with one set of clones. The clones to either side of those looked fantastic in comparison. (They just came down last night)

Despite my issues mid flower, I got some of the best flower I've grown yet under LED. And my next round should be even better.

f-e said:

If you join the dots, a picture can be made where IR is the main culprit. Or, a picture of a penis. It depends what you want to see at this point.

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I grow in coir, drain to waste. When I switched both veg and flower to LED, temps in the rooms dropped and the plants started taking less total volume. I've always assumed the differences were caused by slower transpiration, not a change in spectrum. Could be both, I guess but increasing EC slightly at the same proportions I used with MH solved any issues I had.

GOT_BUD? said:

My biggest challenge will be trying to determine what to use for long release amendments for heavy feeders.

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Same here... I was thinking more Feather meal for N and Rock Phosphate for P and keep feeding kelp extract and fish Hyd like a mofo..

Got a product for free where I bought the Led , its called Led Protekt and has bio available minerals with Salcydic Acid..thers lots of magnesium and manganese , potassium and some silicates....plants love it...same response of when I give em aspirin!!