LED and Calmag issues.

jarvild said:

Why do outdoor and greenhouses use shade cloth during summers ? And yet they are lucky to get 16 hours of light at the summer solstice while we try to run 18+ for veg.

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I don't know of any grow lights putting out lumens/par coverage comparable to the sun, so maybe that's the difference?

I've ran 24hrs all the way down to 16/8 and 24hrs grow faster. Maybe you're on to something though. I'm not knowledgeable enough to be able to tell you.

Two of the three plants went deficient in calcium over the past few days, seeing a few (very few though) rust spots on some of the upper growth.The same leaves also have very slight burning on the tips. What's the connection, what spiked or what got locked out, or something else happened? They're watered once every day with 20-30% run-off. PPM was between 400-450 (500 scale). Run-off as mentioned a few posts back, is always lower than what I put in.

BTW, the new bottle has arrived. Can go up to 2.5ml again. 4th week will be up in a day. Also going forward I believe the 1-0-0 on the new GH calmag should be better than the 4-0-0 on the AN calmag.

Edit:

PH was 5.7/5.8.

400-450 ppm is to low for flower.

jarvild said:

400-450 ppm is to low for flower.

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I know but as Calmag was cut down to 1ml, the PPM pretty much dove. Been working it up slowly but don't plan on going over 600-650.

@Dr. Who if you got that cuticle article, or wax layer article I think it might be good to drop it here.. I wonder how much it applies to the differences in lighting technologies..??

Or just the link to your thread, I can't find it rn..

EDIT:
Found it...
https://www.rollitup.org/t/new-views-on-pm-and-rh.987513/

ChiefRunningPhist said:

I wonder how much it applies to the differences in lighting technologies..??

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I have pondered that myself. Not sure there would be much, if any. Based on same or close light intensity delivery being the same or close.
Less, I expect no real differential impact.

Dr. Who said:

I have pondered that myself. Not sure there would be much, if any. Based on same or close light intensity delivery being the same or close.
Less, I expect no real differential impact.

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Ya, I was thinking about the proximity at which LED are hung vs what HID are, and the perceived differences in results.

I have only read the first post on this thread so I have no idea what has been said etc.....

I kept hearing about the calcium issue and seeing my plants not responding to the nutrients I have been using for HPS for over a decade. It was winter so the stores I go to had very few selections and nothing that was just calcium...

On my next transplant I added about 6 tablespoons of Bonemeal to the bottom 1/10th of soil in my 2.5 gallon container.
The issues cleared up from that point forward.

I thought it was because I fixed the calcium issue with the calcium that is in bonemeal but after reading the first post, it very well could have been the phosphorus from the bonemeal. Either way, my solution has been to add quite abit of bonemeal.

So here is a pic of 2 plants from cuttings, both side by side under LED's. The left is in coir fed 500 ppm daily and the right is in Ocean Forrest with plain watering every other day
So just from my experiments, I see issues with the nutrient profile more than I do with environment.

jarvild said:

So here is a pic of 2 plants from cuttings, both side by side under LED's. The left is in coir fed 500 ppm daily and the right is in Ocean Forrest with plain watering every other dayView attachment 4315192
So just from my experiments, I see issues with the nutrient profile more than I do with environment.

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I have a strain since lot of years ago that looks exactly like yours

Seeing a few rust spots on the sug leaves as well, almost 5 weeks in (8 weeks strain as per SB).

Calmag has been back to 2.5ml/g for the past 5 days. Using RO, silica brings the PPM to 20 and calmag bumps it up to 250. Should I add more calmag at this stage or is it not required this late in?

Total PPM currently is at 525, PH is 6.0. Using only GH Flora trio and silica.

charsi420 said:

Seeing a few rust spots on the sug leaves as well, almost 5 weeks in (8 weeks strain as per SB).

Calmag has been back to 2.5ml/g for the past 5 days. Using RO, silica brings the PPM to 20 and calmag bumps it up to 250. Should I add more calmag at this stage or is it not required this late in?

Total PPM currently is at 525, PH is 6.0. Using only GH Flora trio and silica.

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I'm no expert, but that Ca-Mg 230ppm to the 525ppm total seems high.

ChiefRunningPhist said:

I'm no expert, but that Ca-Mg 230ppm to the 525ppm total seems high.

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Not exactly a gallon. I've been reducing the water by a few ml to raise the overall PPM over the past few days. Was 425 on Monday. 230 is for about 3 - 3.2 litres.

Also run-off is finally back to about 50 points plus than what's being added, till 3 days back it was lower than what was going in.

Im not sure that we can continue here but i will try..
I've read and read and read.
Im under LEDs, having Cal or Mag issue since i started.
I read several times that, when you are under LEDs your LST should be room temperature or -1° or -2°.
When it is 29.5°C in my room temps, my LST is often 4 or 5° less. Measured with two different IR guns.
VPD depends on Room temperature, Leaf temperature and humidity. The bigger the gap between leaf and room, the bigger VPD problem you have.
Is someone experiencing such cool leafs?
For example at the moment, i have 28.5°C room temp, 24.5°C leaf temp, 58% humidity. Which gives me a VPD of 0.8. Im in mid flower. Thats a low VPD. My theory is that with such a low VPD, the plants have to force their transpiration, using calcium ang magnesium which directly involved in that process. A low VPD can cause as much trouble as a high VPD.
What i dont understand is why i have such a difference in temperatures between Room and leafs.

Very interesting post, @Impregnant
This whole VPD thing with cannabis is also what I am struggling with.
For example you tell that you have a low VPD of 0.8.
But in commercial greenhouses they often aim at a VPD of 0.5!
0.8 is ok for them, but they want to stay below 1.
Now I know that the charts for cannabis that you see online, often talk about a VPD of 1.4 or 1.5.
I can't find any scientific papers how they came to the conclusion that these are the right numbers.
I am not saying they are wrong, but I want to know the source.

As you know led lacks the radiant heat that HPS has.
A lot of growers replaced their HPS's with leds, but they didn't change anything else in their room.
They still have the exhaustion fan sucking out air above their lamps; controlling humidity with this exhaustion fan as well; fans blowing on the canopy.
Great for HPS but no so for led.
So perhaps you could raise your leaf temperature by changing a few things in your grow room?

Keesje said:

Very interesting post, @Impregnant
This whole VPD thing with cannabis is also what I am struggling with.
For example you tell that you have a low VPD of 0.8.
But in commercial greenhouses they often aim at a VPD of 0.5!
0.8 is ok for them, but they want to stay below 1.
Now I know that the charts for cannabis that you see online, often talk about a VPD of 1.4 or 1.5.
I can't find any scientific papers how they came to the conclusion that these are the right numbers.
I am not saying they are wrong, but I want to know the source.

As you know led lacks the radiant heat that HPS has.
A lot of growers replaced their HPS's with leds, but they didn't change anything else in their room.
They still have the exhaustion fan sucking out air above their lamps; controlling humidity with this exhaustion fan as well; fans blowing on the canopy.
Great for HPS but no so for led.
So perhaps you could raise your leaf temperature by changing a few things in your grow room?

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Humm...
That would be very funny, after all this time, to run after something that is 100% bullshit. Indeed i reefer to that chart where you read that for a bloom stage your plant should be between 1.2-1.6 VPD.
You said that greenhouses aim for 0.5! Can i ask you where you got this info that i can check it by myself.
Another strange fact:
During hot days, while the lights are OFF, i can measure same temperature between leafs and room.
While the lights are ON, it could be more than 30degrees un the room, and i’ve already measures my leafs being at 24-25 degrees. They are cooler when the lights are ON than when the lights are OFF.
Im in RDWC so i was thinking that running a fresh water, could have something to do with it. So i raised my water temperature from 17,5 to 20 celsius. It didn’t changed leaf temperature.
Tonight, i tried to raise my lights up, thinking that maybe too much light could « block » something. I also lower my extraction. The temperature of the room didnt changed that much, but the leaf temperature changed. I was able to reach the -2 degrees between room and leaf, and i think that was one of the first times. For the first time i reached a 1.4 VPD.
Im not sure yet, but there is something around this. What if leaf temperature was related to something like too much light, causing worst VPD. I really observed that increasing room temperature, did not changed the temperature of my’leafs!
The humidity in the room change between 45 and 65%. I tried to lower the humidity when i was in the 65% area by plug in my dehumidifier, trying to increase my VPD. It did not work!! I raised temperature but it was almost impossible to lower humidity. It is a 400W dehumidifier!
It is really like the plants are setting themselves the right amount of humidity in the room. It is like they can enter in sleep mode, lowering their leafs temperature or raising the general humidity. This is nothing scientific, this is just a feeling that i have. I really observed some strange things while i was testing this and that.
Next thing i am gonna do is to replace 2 of the 5 Quantuum boards that i have, by two 315W CMH.I will try to observe any change in their behaviour compared to the full led set up.

Impregnant said:

During hot days, while the lights are OFF, i can measure same temperature between leafs and room.
While the lights are ON, it could be more than 30degrees un the room, and i’ve already measures my leafs being at 24-25 degrees. They are cooler when the lights are ON than when the lights are OFF.

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i mean they open their stomata when light is on, so they trasnpire water and naturally act as a evaporation cooler.
so that fact alone wouldnt make me wonder ?
keep us updated of your findings.

Most of the scientific papers that I read are not in English, so I guess not very helpful for you.
But in this paper of Michigan State University you can read it as well.
But I am not saying that a higher VPD for cannabis is not the right thing to do. I just wonder where they base these higher numbers on.
The cannabis scene is known for their bro science, or 'because Ed Rosenthal said so'. But I like science papers better

I guess your leaves are the same temperature in the dark period is because they stopped evaporating. So nothing is cooling them then, and then the temperature of the leaves is slowly reaching the temperature of the room. I think in english it is called thermodynamic equilibrium.

May I ask you why you keep your water temperature at 17.5 Celsius?
20 is ok, and a bit warmer roots might help the transportation of nutes as well.

There is a relation between the amount of light and VPD, but even scientist don't know exactly what. I tried to understand what they wrote, but stopped reading it. So fucking hard to understand. But I wonder if you would notice any difference as long as you are not going above 1500umol/s per m2.

A dehumidifier is a nice machine, but if you keep on sucking in fresh air all the time, it is of not much use. Dehumidifiers work best in sealed rooms.

Keesje said:

Most of the scientific papers that I read are not in English, so I guess not very helpful for you.
But in this paper of Michigan State University you can read it as well.
But I am not saying that a higher VPD for cannabis is not the right thing to do. I just wonder where they base these higher numbers on.
The cannabis scene is known for their bro science, or 'because Ed Rosenthal said so'. But I like science papers better

I guess your leaves are the same temperature in the dark period is because they stopped evaporating. So nothing is cooling them then, and then the temperature of the leaves is slowly reaching the temperature of the room. I think in english it is called thermodynamic equilibrium.

May I ask you why you keep your water temperature at 17.5 Celsius?
20 is ok, and a bit warmer roots might help the transportation of nutes as well.

There is a relation between the amount of light and VPD, but even scientist don't know exactly what. I tried to understand what they wrote, but stopped reading it. So fucking hard to understand. But I wonder if you would notice any difference as long as you are not going above 1500umol/s per m2.

A dehumidifier is a nice machine, but if you keep on sucking in fresh air all the time, it is of not much use. Dehumidifiers work best in sealed rooms.

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I was keeping my water that fresh because i was thinking it could be better for disolved oxygen, and also pythium safety. But this domain is also foggy...
I was keeping my lights at what the manufacturer says, so 40-50cm in bloom. But 5 quantum at this distance is a lot of light. I wonder why in many grow rooms, it looks like the lights are at 4 or 5m above the canopea. What is the relation between hight, and lost of photons?
In which language are the scientific papers that youve read?