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More gypsum (aka calcium) for potted tomatoes?

Posted by gman68558 z10 So Cal (My Page) on
Thu, Jul 17, 08 at 13:27

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.

Opinions?


Follow-Up Postings:

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RE: More gypsum (aka calcium) for potted tomatoes?

  • Posted by tapla z5b-6a MI (My Page) on
    Thu, Jul 17, 08 at 15:07

Generally the 5:1:1 mix has lime added, unless there is a specific reason you want to keep pH extra low, <5.0.

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.

Al


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RE: More gypsum (aka calcium) for potted tomatoes?

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?


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RE: More gypsum (aka calcium) for potted tomatoes?

  • Posted by tapla z5b-6a MI (My Page) on
    Thu, Jul 17, 08 at 23:46

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.

Al


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RE: More gypsum (aka calcium) for potted tomatoes?

Gypsum [land plaster] will not change your PH. I use land plaster all the time. It worked for me.


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RE: More gypsum (aka calcium) for potted tomatoes?

  • Posted by tapla z5b-6a MI (My Page) on
    Fri, Jul 18, 08 at 20:16

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.

Al


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RE: More gypsum (aka calcium) for potted tomatoes?

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?


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RE: More gypsum (aka calcium) for potted tomatoes?

  • Posted by tapla z5b-6a MI (My Page) on
    Fri, Aug 1, 08 at 23:58

Garden soil is also a raw-earth material known to contain some lead. If you're that concerned, ask for reagent grade CaSO42(H2O) or hydrated calcium sulfate.

Al


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