Calcium versus Magnesium deficiency

[Maximo]

I was unable to find a good reference to show the difference between a Calcium deficient plant and a Magnesium deficient one. Experience is the best teacher and I have learned now to tell the difference. These images are as much for my reference as everyone else's. The past ten days I've been giving them lots of Epsom salt - Magnesium and generally the leaves green back up, but this time they didn't. On closer inspection the signs are a reverse of a Magnesium deficiency, ie. vein chlorosis, not interveinal chlorosis.
Another sign of Calcium deficiency is the oldest leaves die off, almost as if from nutrient burn. However the nutrient concentration is only 400 PPM for the small plants and PH around 6.0.

Treatment advised: Calcium Nitrate or any Cal-Mag.

My nutrients are 50/50 Maxigrow/Maxibloom. Prior to growing, the clay pebbles were washed to 0 PPMs with Reverse Osmosis water. The depletion was a mistake and in future, a priming with a generous amount of Calcium and Magnesium will prevent issues.

Reference image:

 

[Saibot]

I'm going to respectfully disagree. A calcium deficiency typically manifests as mottled brown spots on the leaves. Magnesium deficiencies cause interveinal chlorosis. Vein chlorosis is more typically a symptom of the over-application of an herbicide or pesticide, or in some cases it is the result of a virus.

Have you used Neem oil? What are you using for a root inoculant?

 

[Saibot]

Do you have pest strips in the grow room? Have you sprayed a pesticide of any type near the plants? Are they near an open window where pesticides may have drifted in? I'm leaning heavily in the direction of a chemical causative.

 

[Saibot]

Maybe Hyoscymus III disease jumped species from tobacco to your plants for the first time ever and you are Ground Zero for a catastrophic epidemic that will decimate the cannabis world and leave us all clamoring for a resistant variety. Or... maybe not.

 

[Saibot]

And yes, I'm just trying to get my post count back up again so I'm not stuck in Nooberville.

 

[Maximo]

There are no disease or pest problems present, hence no chemical pesticides nor additives.

This is hydroponics with clay pebbles that often lack these minerals, especially under LED lighting.

All previous successful grows under the same conditions had no signs of mineral deficiency.
Only this time all minerals were leached out of the media by soaking in RO water days prior to to use.
The pebbles were then allowed to dry out completely and then soaked with 300ppm Maxigrow @ PH 6.0.

Some 2 part hydroponic solutions contain as much as 50/50 Calcium Nitrate to other minerals.
Though I will not be using that much with Maxigrow, but supplementing more Ca will certainly help.

Here's a two zip from last grow..

 

[Saibot]

I'm curious then, only because vein chlorosis is so rare and not a typical indicator of a calcium def. If you're supplementing with calcium I guess time will tell. If you don't mind I'll stick around and see how this grow turns out.

 

[Maximo]

I got a 2nd PH meter yesterday and it was reading a full point lower than the other meter (both calibrated to a PH 7.0 buffer).
The PH was really tipping below 5.5, so that's what was locking out the Calcium. The lower the PH, the less calcium available. Unfortunately unlike Magnesium the leaves will not restore to full health as Calcium is an immobile nutrient. So, only new leaves will show improvement with the nutrient restored.
The photo taken is of the worst affected one.

 

[Saibot]

Good to hear from you! How is your plant doing now, Maximo? I'm hoping that bringing the pH into the proper range will make her happy and get her growing for you. Best of luck and I'm looking forward to future pics.

 

[Saibot]

I showed the photo of your plant to a Washington State University county extension agent. He's like the grow guru of everything. First words out of his mouth, "That's caused by chemicals. Could be something like RoundUp or maybe a pesticide."

Your problem has me curious, only because veinal chlorosis is so rare. He also is interested in seeing if your diagnosis is correct and treatment is successful.

 

[Maximo]

All three strains exhibit the same signs, though vary in their susceptibility. Pesticides and herbicides are ruled out. The area is closed off from spray drift or usage from afar.
I do remember using a lot less PH down in previous grows, so the cheaper PH meter was not to be trusted.

 

[Saibot]

Wow! You have a beautiful setup, Maximo. Very impressive!

Just a shot in the dark, but is it possible that there is some chemical IN the system?
I have no doubt that you know what you are doing and I hope that getting the pH corrected solves that problem.
I hope I'm not being a pain in your butt, and apologize if I am.

 

[eggzin]

I just happened by. I'm new at this, but I've been reading a lot. I thought I'd throw this out there.

I remember reading that too much magnesium can lockout calcium. Although I realize the discussion is centered now around "is this an actual calcium deficiency".

Maybe it's a side effect of Epsom salt....

 

[Maximo]

With Magnesium the leaves are restorable to a healthy green. That isn't the case here, since Calcium is an immobile nutrient the affected leaves are not restorable. The plant must outgrow the condition, which shows up in new growth.
Gladly the plants are outgrowing the condition.

 

[Weaselcracker]

I sure love those few correctable deficiencies. Iron def is another I've had, and its a lovely sight to see it leaving again.

 

[Saibot]

I'm glad to see that they're looking healthy again, Maximo!

 

[Maximo]

Recovery was slow but good, looking forward to these autos.

 

[Maximo]

Looking good now.

 

[eggzin]

Yes, they look very good.

Do you conclude that correcting the ph rectified the problem or were there other steps you took that, possibly, solved the problem --for example, correcting for possible chemical contamination?

 

[Scientific]

Wouldn't magnesium nitrate or magnesium carbonate be better than magnesium sulfate (Epsom salts)? I cant' help but wonder if that sulfate moiety in Epsom salts might be bad for the plant.

I'm also really dubious about how plants have different nutrition requirements under different light sources. I could understand that if you were growing under, say, pure red or pure blue light, but I have a sneaking suspicion that the notion that plants need different nutes under LEDs is just folklore growing out of concern about this new, weirdly colored light source. (Having said that, I will freely admit that I could be wrong, but I'd really like to see some scientifically rigorous measurements to corroborate this.)