LED and Calmag issues.

xtsho said:

Calmag is the most overused additive there is. Calmag issues go away if your nutrient uses calcium nitrate for the nitrogen source. Its more expensive than the other sources but it's much better. Provides both nitrogen and calcium. Nutrients that don't use it for their main nitrogen source typically also have their own brand of calmag. That's so they can make you pay again for something that should already be in their base nutrients. It's not LED related it's nutrient related.

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I agree, brother! All fertilizer especially made for C. should have at least half the nitrogene added in form of calcium nitrate. The whole calmag line is just to make more profit. But its neither a nutrient nor an LED issue. It's because of the VPD! Keep your VPD in a healthy range and there is almost no difference to HPS.
With HPS the humidity is most of the time in a healthy range and lots of growers have never seen VPD issues. They have never seen such issues and many don't even know what it is, me included, lol!
Fact is, the plants can adjust themself within a certain range because of the radiated heat.

With "cold" LED light we need a higher ambient temp to get the leaf temps in the optimal range and a higher humidity is neccessary but usually air tends to dry out with higher ambient temps which makes it neccessary to regulate the humidity manually. As soon as you maintain a healthy humidity range the plants "feel" happy. There are a few good video's on youtube about VPD. I like this one cuz it's detailed and fast explained..

xtsho said:

There are tons of growers using LED's that don't have any issues with calcium or magnesium deficiencies.

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I'm betting they are hard water areas with abundant Cal/Mag in the tap water.

budman111 said:

I'm betting they are hard water areas with abundant Cal/Mag in the tap water.

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Yes, 400 ppm out of the tap here with almost 300 ppm of that as cal-carbonate.

jarvild said:

Yes, 400 ppm out of the tap here with almost 300 ppm of that as cal-carbonate.

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I'm only 20 PPM tap water here, get away with some brown spots on leaves with HPS without calmag but LED is a whole different ball game for Calmag consumption.

Has anyone tested what's actually in the Ca-Mg products they are adding? Im guessing its got a decent amount of K..

I'm guessing lots are thinking issues are Ca-Mg and when they add it and the shit gets better they think Ca-Mg, but GH Ca-Mg is definitely not close to a clear product. CaCO3 & Mg(NO3)2 are white salts that shouldn't give much color to RO water...

Magnesium Nitrate solution...


Calcium Carbonate solution...
This was the only sample I could find, but its saturated and GH isn't, so imagine lots less, and lots clearer...


Kelp...


GH Ca-Mg...



I'm venturing a decent amount of Kelp is added. I also think we've misdiagnosed how much K cannabis wants and that many Ca-Mg issues are actually K issues, (EDIT: but that's not really supported by the addition of Kelp to Ca-Mg like I was initially thinking lol)

@Randomblame when my plants show begining symptoms the leaves are hot. Should that trigger stomatal closure? I can't figure why it doesn't regulate itself like the HPS does, when it gets too hot?

ChiefRunningPhist said:

Magnesium Nitrate solution...
View attachment 4302266

Calcium Carbonate solution...
This was the only sample I could find, but its saturated and GH isn't, so imagine lots less, and lots clearer...
View attachment 4302267

Kelp...
View attachment 4302265

GH Ca-Mg...
View attachment 4302268


I'm venturing a decent amount of Kelp is added. I also think we've misdiagnosed how much K cannabis wants and that many Ca-Mg issues are actually K issues, (EDIT: but that's not really supported by the addition of Kelp to Ca-Mg like I was initially thinking lol)

@Randomblame when my plants show begining symptoms the leaves are hot. Should that trigger stomatal closure? I can't figure why it doesn't regulate itself like the HPS does, when it gets too hot?

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Missing far- and infra-red radiation! For that reason we need higher ambient temps and RH to control transpiration youself. When the VPD gets too high the plants don't feel okay and the whole nute system runs out of balance. They took up too much Ca and because Mg is the natural antagonist you see Mg deficit first but if you don't fix the too low humidity you see more and more deficits cause excess Ca looks out other metals too. Within 2 or 3 weeks its impossible to figure out what it is cuz in week three Fe, K, P , Zn aso are also looked out.
All this issues can be avoided by keeping the humidity in a healthy range.
If temps and humidity is in the right area and you get nutrient issues it must have another reason.

Also make sure you don't use too much light. 50klx are ~750μMol/s/m² and above that level it gets more difficult to keep them happy. I see first signs of bleaching above that level without added CO².

Stomata breathing is normally regulated by blue light(signalling) but when the plants receive too much sun light she recognize the heat radiation and she close the stomata to reduce transpiration and she would try to turn the leaves away from the light. In such a case the blue light command(keep stomata open) gets over written! With HPS its almost the same because of the used tech.
With LED light there is no IR radiation an only very little far-red. So under conditions with too much light or too low humidity
there is no command telling the plant to reduce transpiration. She(her leaves) gets too warm and she tries to cool herself by transpiring even more water cuz the blue light tells her to keep the stomata open.

To regulate transpiration under LED you are forced to keep an eye on your VPD. Hot leaves(higher like the ambient temps) are usually a sign of too much light or a too short distance. With LED stabilized leaf temps should be the same or 1°C lower like ambient temps.

Randomblame said:

Missing far- and infra-red radiation! For that reason we need higher ambient temps and RH to control transpiration youself.

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Both of those EM ranges provide heat to the leaf, they are photons like PAR. Is their significance greater than I'm giving credit too? Blue photons give heat as well when they downgrade energy levels. One heat opens, the other closes?

How much hotter do leaves using HPS get than LED? When my leaves started showing symptoms the temps jumped to 87f/30C LST.

And then just one more question lol, are these symptoms consistent for people using MH for flower (some use only MH in flower)? Or T5HO?

Randomblame said:

Stomata breathing is normally regulated by blue light(signalling) but when the plants receive too much sun light she recognize the heat radiation and she close the stomata to reduce transpiration and she would try to turn the leaves away from the light. In such a case the blue light command(keep stomata open) gets over written! With HPS its almost the same because of the used tech.

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So when people mix MH & HPS the blue from MH isn't enough to override the command?

Randomblame said:

With LED light there is no IR radiation an only very little far-red.

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Got it. Its a pretty low ratio right? If I added far red & IR at ~7% (or what you think?) that should fix it?


If raising ambient achieves the stomatal closing, then I'm guessing that my LST temp of 87f/30C needed to be higher, ... but that means Id have to raise my ambient over 30C?

Two much b!ue is also counter productive(more like 12%). Blue photons carry twice as much energy like red photons. Plants use this stored energy to drive certain processes like PS. But too much high energy photons can cause what we call bleaching. Bleaching usually looks like this..



... and has nothing to do with nutrients or VPD.
Its another problem cause by too much light and under HPS you don't see that because 1. the lower intensity and 2. the low output in the blue range. I've seen bleaching the first time as I've tried to use a single ended 1000w bulb with increase blue range above 1m². But with LED I've seen it many times and most of the time you see it first on the upper leaves.
Optimum amount of blue for a flowering spectrum is probably 8-10% so it is no wonder that 3000°k has always the highest yields of all spectrums.
Red photons can be converted much easier internally cause of the lower amount of energy stored inside the photons. The closer the wavelengths are to the peaks of PS-I and PS-II(680 and 700nm) the easier for the plant to use them.

Randomblame said:

Stomata breathing is normally regulated by blue light(signalling) but when the plants receive too much sun light she recognize the heat radiation and she close the stomata to reduce transpiration and she would try to turn the leaves away from the light. In such a case the blue light command(keep stomata open) gets over written! With HPS its almost the same because of the used tech.
With LED light there is no IR radiation an only very little far-red. So under conditions with too much light or too low humidity
there is no command telling the plant to reduce transpiration. She(her leaves) gets too warm and she tries to cool herself by transpiring even more water cuz the blue light tells her to keep the stomata open.

To regulate transpiration under LED you are forced to keep an eye on your VPD. Hot leaves(higher like the ambient temps) are usually a sign of too much light or a too short distance. With LED stabilized leaf temps should be the same or 1°C lower like ambient temps.

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According to this, heating up the leaves causes stomata opening. Hmmm. Aren't HPS leaves hotter than LED? If plants wilt from the intensity of the suns SPD and HPS is similar, shouldn't HPS be wilting and transpiring the plants too, i.e. be effected by VPD? Shouldn't they be just as bad of transpirers as plants under LED? If the LEDs are cool, why are they transpiring more? If it's because of the blue spectrum, then shouldn't adding heat, ie ambient only exacerbate?

https://homeguides.sfgate.com/plants-wilt-hot-summer-day-76564.html

https://water.usgs.gov/edu/watercycletranspiration.html

Lol I always thought adding heat was closing stomata too! Mainly because I read stuff like that on here and never even looked. I wonder if everyone has been completely thinking wrong about this all along lol... Adding heat was actually increasing transpiration lol

Consequently an unmanaged or lower VPD, in an HPS setup, should actually transpire like mad! So the switch to LED and trying to slow transpiration is puzzling, considering the HPS doesn't see these issues, yet, should suffer from it the most. If increasing VPD works, then perhaps it's just over concentrated nute ratios that ironically LED growers are doing more than HPS growers? Seems unlikely (though its the only thing I can think of right now). So what is happening?

Hello,

I hope everyone is having a great grow. I run 2800 watts of Vero29 COBs. My tap water is ~20 ppm (.5 scale). I use jacks nutrients with epsom. From my own experience, I found I used the same mix as when I used HPS. As others have stated, I found keeping VPD in check along with proper light intensity to be two extremely important factors for success.

In this example the plant has just a too small root system and they transpire more as they take up. Same thing you can see with seedlings or cuttings with not enough root. And wind is another thing.

If they wilt or not depends also on how long the plants receive such intense light. If it's only for one hour or so they can handle it better. It depends also on type of plants cause they have different strategies to deal with too much heat. As I have said above blue light tells the plant to open the stomata and plants which are not used to deal with more heat naturally would leave the stomata open and when they have a too small root system they transpire to the death.
Sun light and HPS cause ~3°C hotter leaves temps against ambient. With 30°C in summer leaf temps would be ~33°C. Still no reason to close the stomata. But with 40°C ambient for instance an C. plant would reduce transpiration and try to reduce the surface area. If they have big enough roots they can withstand such conditions for a while.
When blue light tells the plant to keep the stomata open and nothing tells them to close them they would stay open as long as its bright. And what's at night? No blue light at night but the plants still regulate the stomata breathing with the help of heat. Less heat, less transpiration. More heat, more transpiration. Too much heat and they try to reduce transpiration and open the stomata again when the temps are back in a good range.
Some species have working strategies to survive such conditions others not.

One huge factor for transpiration is the humidity. In summer with 30°C we usually have a higher humidity in temperate zones outside which means the VPD is in a healthy range.
But that's not the case in a tent. With LED's and 30°C the humidity goes down to 30% or so. Especially when the plants are small that's a huge problem.
I can say it as often as you want, you need the right conditions in a grow room and especially with LED its important to keep the VPD in check. Temps and humidity has to stay in balance.

Randomblame said:

In this example the plant has just a too small root system and they transpire more as they take up. Same thing you can see with seedlings or cuttings with not enough root. And wind is another thing.

If they wilt or not depends also on how long the plants receive such intense light. If it's only for one hour or so they can handle it better. It depends also on type of plants cause they have different strategies to deal with too much heat. As I have said above blue light tells the plant to open the stomata and plants which are not used to deal with more heat naturally would leave the stomata open and when they have a too small root system they transpire to the death.
Sun light and HPS cause ~3°C hotter leaves temps against ambient. With 30°C in summer leaf temps would be ~33°C. Still no reason to close the stomata. But with 40°C ambient for instance an C. plant would reduce transpiration and try to reduce the surface area. If they have big enough roots they can withstand such conditions for a while.
When blue light tells the plant to keep the stomata open and nothing tells them to close them they would stay open as long as its bright. And what's at night? No blue light at night but the plants still regulate the stomata breathing with the help of heat. Less heat, less transpiration. More heat, more transpiration. Too much heat and they try to reduce transpiration and open the stomata again when the temps are back in a good range.
Some species have working strategies to survive such conditions others not.

One huge factor for transpiration is the humidity. In summer with 30°C we usually have a higher humidity in temperate zones outside which means the VPD is in a healthy range.
But that's not the case in a tent. With LED's and 30°C the humidity goes down to 30% or so. Especially when the plants are small that's a huge problem.
I can say it as often as you want, you need the right conditions in a grow room and especially with LED its important to keep the VPD in check. Temps and humidity has to stay in balance.

View attachment 4302390

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I agree with you about good grow conditions.

All things being equal, LED requires an increased VPD compared to HPS, and historically, on this site at least, its been defined as HPS being hotter thus they reduce transpiration, and thus why LED would need higher VPD, but.... we see that's not the case, in fact this temperature relationship is reversed.

Could you post that blue light stomatal correlation data for me?

If the blue light is triggering transpiration, ie LED, why does increasing ambient help?

Furthermore, how are the HPS triggered to open?

And finally (ties into the previous question), if the sun isn't hot, ie <40C, why isn't the blue from the sun causing over transpiration? MJ grows in the mountains in arrid climates too.



@Randomblame I'm not trying to refute the fact it works, if it does, but I think the current explanation has many inconsistencies and I can't help but think there's something different at play. At the very least you have to admit these are compelling questions. Ive thought it could be EMF generated by drivers or lights considering the close proximity, but just a guess...

Ok I found something on blue light.
Here's the link...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5462062/#!po=0.505051

Just some interesting things I didn't know earlier...


I agree VPD is an important metric, but I think when it comes to LED, it's only managing symptoms of a different and separate issue other than what it's typically blamed for (LST & blue) when comparing the 2 types of light. The data I've seen doesn't seem supportive that VPD is the sole reason to blame when comparing the differences on the plants between the 2 types of light, mainly considering the subjective application of increased VPD to a sample (LED), in what seems to be to me, in direct contradiction to the original VPD application reasoning (it's backwards!). The reason given is subjectively applied to LED though other sources could fit the mold and don't. There's other inconsistencies as well. I think VPD could possibly be treating a different issue than transipration rates, considering the rules aren't seemingly universally applicable.

You could be right too! lol, idk, I'm just saying there are inconsistencies.

Curious what hydroponic sunlight growers notice? Or T5HO?

ChiefRunningPhist said:

Ok I found something on blue light.
Here's the link...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5462062/#!po=0.505051

Just some interesting things I didn't know earlier...
View attachment 4302401 View attachment 4302402

I agree VPD is an important metric, but I think when it comes to LED, it's only managing symptoms of a different and separate issue other than what it's typically blamed for (LST & blue) when comparing the 2 types of light. The data I've seen doesn't seem supportive that VPD is the sole reason to blame when comparing the differences on the plants between the 2 types of light, mainly considering the subjective application of increased VPD to a sample (LED), in what seems to be to me, in direct contradiction to the original VPD application reasoning. The reason given is subjectively applied to LED though others sources could fit the mold and don't. There's other inconsistencies as well. I think VPD could possibly be treating a different issue than transipration rates, considering the rules aren't seemingly universally applicable.

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Here's what I've noticed, and I'm no science whiz, so bare with me a moment lol.

In my space, temps are too low and humidity is too low under my LED which is 287W true.

The conditions are actually slightly worse under the 600W HPS, with temps being lower and humidity being slightly lower.

In the tent, it's easy to light burn with the LED at less than 20". I can put plants at around 14" under the HPS with no ill effect.

So, it appears to me, that the LED spectrum is too strong for those temps, photosynthesis is low and transpiration is high, causing burns and over nutrition because of the increase in uptake but reduction of processing that uptake. Hits the top of the plant first.

Under HPS, the temps are lower than the tent EXCEPT on the canopy, increasing photosynthesis and therefore using up the increased nutritional uptake which reduces the importance of humidity in comparison.

Hope that makes sense.

ChiefRunningPhist said:

Both of those EM ranges provide heat to the leaf, they are photons like PAR. Is their significance greater than I'm giving credit too? Blue photons give heat as well when they downgrade energy levels. One heat opens, the other closes?

How much hotter do leaves using HPS get than LED? When my leaves started showing symptoms the temps jumped to 87f/30C LST.

And then just one more question lol, are these symptoms consistent for people using MH for flower (some use only MH in flower)? Or T5HO?

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HPS, MH, CMH and even T5 have similar heat radiation like sun light. They all increase the leaf surface temps more like CRI80 LED's. Plant have addapted to sun light millions of years so one coulpd say, they are used to a certain ratio of light and heat. With LED its like they get a new type of light. A light that doesn't contains 15-30% heat radiation. For this reason the leaf temps are almost the same like the ambient temps with LED's. But plants are used to light thats heats up the LST more like that. They are used to light that heats up their leaves higher like LED's and because they don't get it the transpiration runs out of balance. CRI90 works already much better than CRI80 because it has twice as much far-red. A friend have switched from 3k/CRI80 F-strips to 3k/CRI95 Nichia boards and even with higher amounts of light there is no bleaching anymore and the plants look much better and less stressed. In many tests CRI90 has shown a signicicant reduce in flowering time without much loss in yield. To me that means something and I add far-red to my light spectrum since 4 years now.

I'm no prof and can only explain it to a certain degree. Not all species can handle heat and dry conditions in the same way.
Fact is, the missing far and infra red makes it neccessary for us to control transpiration manually by keeping the VPD in a healthy range.
If you maintain lets say a VPD of 0,4-0,8kpa for the seedling stage, 0,8-1,2kpa for vegging and 1,2-1,6kpa in the flowering stage you should not see calmag issues. If you still get issues it must have another reason.

You need also to keep in kind that we usually use a higher intensity now since we have such powerful LED's. No one tries to keep only 500-700μMol/s but that's the range we have used for years with HPS or MH light. When you keep 1000μMol/s/m² with HPS its also more difficult to keep the plants happy. The whole metabolism runs much higher and deficits occur much faster. So IMO the different nutrient demands with LED have also to do with the higher intensity.