More gypsum (aka calcium) for potted tomatoes?

gman68558(z10 So Cal)July 17, 2008

Really getting into tomatoes, and it appears that calcium is particularly important to tomatoes based on the research that I've done so far.

Given this, would it be advisable to up the gypsum in the 5-1-1 mix? Maybe double it, or 1.5x? Or just keep it the same?

Obviously too late for this year, but I am getting hit with some BER so I'm just wondering if this might make a difference for next season.


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tapla (mid-MI z5b-6a)

Generally the 5:1:1 mix has lime added, unless there is a specific reason you want to keep pH extra low, The BER may not be because of an actual Ca deficiency. An imbalance of P or Mg can create antagonistic deficiencies. High humidity levels, and soils that are either too wet or too dry also cause BER. In short, the plant needs a CONSTANT supply of Ca available during the formation of every cell or the cells will be weak/deformed. ANY disruption of the nutrient stream makes greater the probability of a culturally induced Ca deficiency and the accompanying BER.


    Bookmark   July 17, 2008 at 3:07PM
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gman68558(z10 So Cal)

Al, I decided to go with gypsum and epsom salts instead of the lime since the pH of my irrigation water is in the low 8's. I thought I would be in danger of raising the pH too high by using lime. Was I mistaken?

    Bookmark   July 17, 2008 at 3:41PM
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tapla (mid-MI z5b-6a)

My water is in the low 8s too, and I don't seem to have much difficulty except a little with Fe absorption on some plants that assimilate it inefficiently, but I have found a way to easily correct that.

Certainly you can use the gypsum/Epsom salts combo to keep pH low, but it's prolly not really necessary.


    Bookmark   July 17, 2008 at 11:46PM
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Gypsum [land plaster] will not change your PH. I use land plaster all the time. It worked for me.

    Bookmark   July 18, 2008 at 7:13PM
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tapla (mid-MI z5b-6a)

Thank you - we are aware of that, MP. That's why Gman elected to use it - to retain the natural pH of the soil - instead of liming, which would raise pH.


    Bookmark   July 18, 2008 at 8:16PM
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I am concerned about the usage of gypsum, a raw earth material known to contain some lead for treatment of potted tomato blossom end rot. Is there USP grade (for medical use) gypsum available which should not have any lead?

    Bookmark   August 1, 2008 at 10:21PM
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tapla (mid-MI z5b-6a)

Garden soil is also a raw-earth material known to contain some lead. If you're that concerned, ask for reagent grade CaSO4·2(H2O) or hydrated calcium sulfate.


    Bookmark   August 1, 2008 at 11:58PM
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