Need Help,Too much Dolomite in SWC

tomhogMarch 8, 2011

I'm worried that I have used to much Dolomite in my SWC.

I am using the SWC from Gardener's Supply. It has approx a 4 gallon resavoir and holds about 1.9 cu ft of mix. I am using Lamberts potting mix from Home Depot which has Dolomite and limestone listed in the ingredients. I used raybo's instructions from his earthtainer III but halfed the recipie from 2 cups dolomite to 1 cup. Last year I followed it to the T and got blossom drop, BER, and other issues that a local gardener attributed to too high a PH caused by too much lime. SO this year I used 1 cup dolomite and 1/2 cup fert strips.

I am worried that I still over dosed on dolomite at 1 cup in 1.9 cu ft / 50 dry quarts of mix. Does that sound too high given that the bag says it already has dolomite in it to adjust for calcium and ph? Will too much dolomite raise Ph so high that I will have blossom drop and BER? If so, what can I do to fix? Will a soil acidifier help balance it out? I have not planted the plants yet but do not want to scrap all the dirt I just mixed.

Any advise would be greatly appriciated.

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tapla (mid-MI z5b-6a)

The total volume of limestone that should be incorporated into 2 cu ft of a peat or peat/bark based soil is 3/4-1 cup. A pH that is too high will inhibit uptake of multiple nutrients and (primarily) micronutrients.

Here is a pH chart that shows nutrient availability as a function of pH in container media. In container media, plants prefer a pH of about a full point lower than in mineral soils.

For comparison:

Do you see where with high pH you're very likely to have difficulty with insolubility of P, Fe, Mn, Cu, Z and B?


    Bookmark   March 8, 2011 at 10:53AM
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Yes, I see. It makes sense. So, would you think I am ok, adding 1 cup into 2 cu ft that had lime already in it per the pakage or no. How would I remedy the mix so that I dont have to high a Ph? Should I take out some mix and put new mix without lime in it...I just don't want to through away the mix I already have in there. Would a soil acidifier additive work?

    Bookmark   March 8, 2011 at 12:07PM
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tapla (mid-MI z5b-6a)

You probably didn't need ANY lime in it - it was pre-limed to an appropriate pH, and there would certainly be enough Ca and Mg IN the soil already. I don't usually follow the threads that specifically address growing in SWCs, but I'm guessing you missed an important piece of information. It could easily be that someone was offering instructions on how to make a suitable soil from scratch, but you thought the info was to be applied to soils from a bag, already limed. What do you think?

You could always buy pine bark/peat/perlite and make an equal volume of soil w/o lime & then combine the two to come up with a mean level of lime that's more appropriate.


    Bookmark   March 8, 2011 at 2:24PM
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Actually, according to raybo's instructions on his earthtainer, he uses Sunshine #4 Mix, and Premier Pro-Mix BX, both which have the same ingredients that are in my mix, like dolomite limestone. So I assumed since he advocates adding 2 cups of dolomite in his mix that also contains dolomite, that I would do the same, just half strength. He states he uses 2 cups of dolomite with his 3.3 cu ft of mix that his tainer holds. I figured since he has such great success with his formulas, that it would be a good place to start. I am confused. Maybe he can chime in and help me clarify my confusion.

    Bookmark   March 8, 2011 at 2:51PM
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