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Home Forums Grow Community – Ask Questions & Share Your Grow! Magnesium deficiency versus temperatures

  • This topic has 15 replies, 3 voices, and was last updated 3 weeks ago by CamZ.
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  • #3539
    rama777
    Participant

    Okay so first time under LED’s. I’ve had a bit of mag deficiency symptoms through the whole veg so far. My VPD is always 1-1.0 (relative to the actual leaf temps). But, the leaf surface temps have been at around 72-73 degrees most of the time.

    I use 200ppm of calmag with every watering.

    I decided today to use a space heater. So now my leaf temps will be 77-79 degrees most of the time.

    Does the increase in temperature have the potential to help the plant metabolize “better” in such a way as to reduce the mag deficiency symptoms, or must I use Epsom salts?

    Thanks guys!!

    #3540
    reflux1
    Participant

    i could be wrong here but im pretty sure it wont, the only temp related def i have seen, is phos at cool temps

    #3545
    rama777
    Participant

    Cool thanks. Let me throw something else out that I forgot to mention. I sprouted these in a soil that ended up being too hot for them. It didn’t burn them per se but nevertheless is stunted them and 6 weeks in now they are still darker than ideal.

    I know someone who is running these seeds and his have never shown mag deficiency and he hasn’t given them anything. He started his 10 days before me.

    So one thing that I’ve been thinking is that the light mag deficiency could be hastened by the somewhat excessive amount of nitrogen. I have nothing to back that up.

    Of course light intensity comes into question but these plants are super slow pokes. I’ve been slow rolling the hell out of them. 6 weeks old and ppfd is right around 220 now. They only got 150ish par through the first 5 weeks.

    #3570
    rama777
    Participant

    Another thing I’m interested in in case anyone knows the answer..

    So my VPD is around 1-1.1 which is theoretically ideal in the veg stage. I have dark foliage from excess nitrogen in the soil. Nothing crazy now or anything, just not ideal.

    If I kicked the VPD up to 1.2-1.4, I would increase transpiration right? Given my moderate excess of nitrogen still lingering, what effect would raising the transpiration have? Would it send too much nitrogen up and make it worse, or would it help in this context by enabling the plant to push growth and move more swiftly towards achieving a healthier color?

    #3574
    reflux1
    Participant

    plants need more nitrogen than othere nutes in veg,  so they will be loving you more if anything, your npk 111 or 555  will cover all stages in growth

    #3575
    rama777
    Participant

    Okay so here’s where I’m at with the worst one, and some more info. By the way I tried out boosting the leaf temps and that didn’t help. I do understand that magnesium can have issues in cold temps. I’m keeping mine at around 75 degrees right now to save on electric cost.

    They have never been fed any nutrients. The soil was too hot for these plants at germination. They were somewhat stunted in the first 4 weeks. These plants are 6 weeks old. I know, small, but I know someone else growing them (master grower) and his are very small too. Just slow growers.

    Ppfd levels are around 170-190 right now. I’ve experimented going higher but they are just super sensitive. Maybe they can handle more but I don’t want to push anything until I get the mag worked out.

    First two weeks they got just RO water with just enough calmag to stabilize the ph. Since then I was giving them 100ppm of calmag, which I have worked all the way up to 250ppm as of this week.

    Water ph is always around 6.5-6.8

    Light stress is virtually out of the question, yeah?

    I’m down to either add epsom to the calmag in order to bring the ratio closer to one another.

    Or, skip the calmag and hit em’ with just epsom.

    Or, foliar the epsom.

    Of these options, not sure about a wise ppm, or how long, often to add whichever of these options before tapering back or stopping all together.

    Advice greatly appreciated!!

    #3576
    rama777
    Participant

    Oh and VPD is always at around 1-1.10

    Also open to suggestions for lowering or raising that for whatever reason 😉

    #3577
    reflux1
    Participant

    i can see mag def in the older shade leafes,  but very little on the newer leafe thats above them,  to me it looks like there getting better, good job man

    #3578
    reflux1
    Participant

    lots of times,  even with me,  we try to make things so perfect, that some times we can make things worse,  dont, or try not to over process it,  some times  simple is better,  if my plants look like yours,  id be happy, your doing a good job man,  keep it up

    #3584
    CamZ
    Moderator

    Calcium and magnesium are antagonistic despite the fact that they are often applied together. You should 100% hit them with epsom salt only. A foliar could help them immediatly but doesn’t fix the imbalance. Try mixing in 1 tsp per gallon your next watering and give it 2-3 days. If you’re doing a foliar then rule of thumb is quarter strength. Don’t go overboard with the epsom salt though. I wouldn’t do more than 2 successive watering with epsom salt. You have probably been exacerbating the nitrogen tox a bit by using calmag, which is calcium nitrate. I’m about 95% certain you’ll see the issue clear up after the epsom salt. Try bumping ppfd up to 300 too so you can get some juice moving through the leaves. In this case I think it will benefit you more than leaving them turned down. 300 is still way on the safe side.

    #3586
    rama777
    Participant

    Thanks man! Just fyi my calmag is not nitrate derived and has no nitrogen in it.

    I’ll hit them with epsom only on the next watering and then bump the light up after a few days.

    I haven’t used just epsom yet but I did mess with adding it to a gallon to see what the ppms would be. I got 170ppm from 1/8 of a teaspoon. A full teaspoon is going to push the ppm past 1,000 I believe.

    That feels to high to me but I know that people even use a tablespoon. I’m down to try a teaspoon but if you think a target ppm is better, I’m all ears :))

    #3591
    CamZ
    Moderator

    That’s interesting about your calmag. I was under the impression calcium and magnesium were hard to get in the same solution without the attached nitrate. From my understanding, most of the things they were bonded to would trade electrons and fall out of solution. May I ask what you use?

    I am assuming you are starting with very low ppm water? I just checked 1 tsp (not tbsp) gave me around a .95 ec on my calibrated Apera pen. That’s less than 500ppm, which may seem like a lot still but you are correcting a deficiency and an imbalance. Certainly do whatever makes you feel safest. I wouldn’t use less than a half a tsp though. It’s not like the plant is going to use all of it at once. You are just getting it in the medium, but I understand your apprehension.

    1/8 tsp is around .01 ec or 50ppm. The target for normal mag range is 40-60ppm for cannabis. That’s like how much should be in your mix if you were feeding synthetic every watering.

    Hope that helps.

    #3592
    rama777
    Participant

    It does help thanks! I went with a teaspoon, and yeah as I was contemplating how much to use, it did dawn on me that I was correcting an imbalance and not hitting them with something that would shock/burn them so I felt fine about the 450ppm I gave them.

    Roots organics is the calmag I use. Derived from Kieserite and Gypsum.

    As for what to look out for, can I expect the leaves with very light deficiency to green up, or will the signs of a corrective balance be visible exclusively on new growth?

    After perhaps one more watering with just magnesium (I’ll feel that out), going forward, my calmag is a 4:1. I am considering mixing up calmag in conjunction with epsom salt and creating a ratio of 3:1. I figure if it’s imbalanced right now from my calmag, I don’t see why it wouldn’t crop back up without maintaining an adjustment. Sound logic?

    #3593
    CamZ
    Moderator

    Didn’t realize the twitch stream would show in a screenshot lol. That’s a review off Amazon. Seems like other people have had problems with mag deficiency too. That product is more of a slow release, which isn’t really what you want for calmag. If your mix is right then you won’t need calmag anyway. Calmag is more for correcting immediate issues or buffering ro water in hydro imo.

    Yeah, some of the interveinal color should return in the next few days but not all of it.

    Yes, I think you’re on the money with the ratio change. It’s not getting the mag or needs more. Don’t think it’s a lockout but keep an eye out for other strange leaf issues just incase.

    #3594
    rama777
    Participant

    Thanks for the info!!

    I use RO water so the calmag is both a buffer and a mineral replacement.

    I think I’ve heard that 50-60ppm is a solid every watering target for magnesium?

    If that’s true, I’ll work out the math to get maybe a 2.5:1 or a 3:1 using both my calmag and epsom and see how that works out.

    My nutes have calcium and magnesium in them. Maybe when I get to the point of using them I’ll experiment with just adding 75-100ppm of Calmag as a buffer and hope that the nutes take care of the rest.

     

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