Oyster Shell Calcium

Discussion in 'Soils, Fertilizers and Composting' started by moondreamer, Aug 7, 2005.

  1. moondreamer

    moondreamer Member

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    I am having a lack of calcium & magnesium problem with my soil. My organic garden encyclopedia says to use Oyster shell calcium sparingly. I would like to know how much of it in pounds/ounces to use per 100 square feet. Also, would like to know if there is any other calcium source that would not raise the PH. My Ph is 7.0
     
  2. angilbas

    angilbas Active Member

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    Gypsum -- hydrated calcium sulfate -- has little effect on pH. The same goes for calcium chloride, which is often used to prevent blossom end rot on tomatoes.


    -Tony
     
  3. moondreamer

    moondreamer Member

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    Thank you for the info. Do you know a good source to obtain either gypsum or calcium chloride.

    Also, a fellow organic gardener, at it much longer than I, had a conniption about gypsum, but wouldn't say why it shouldn't be used. Does anyone knoiw anything about this? Looked it up in my encyclopedia, it just said that organic gardners are against using this. I put a lot of $ into that encyclopedia, too much for info as lame as they give out.
     
  4. angilbas

    angilbas Active Member

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    Agricultural supply centers often have bulk quantities of gypsum and calcium chloride. Hardware stores sell smaller quantities of calcium chloride as a de-icing agent.

    Gypsum's only undesirable trait is manifested if it is deeply incorporated into a poorly-drained soil. Certain bacteria there carry out sulfate reduction, converting it into hydrogen sulfide and calcium carbonate.


    -Tony
     
  5. growest

    growest Active Member 10 Years

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    moon--Organic farmers often use much less calcium per given area than conventional growers (per Arden Andersen and Elaine Ingham). The idea is to supply the needed calcium, not change pH, and calcium is important but not a "huge" nutrient in terms of tons per acre.

    The above "experts" recommend mixing the oyster shell or whatever with your compost well before application, this can vastly increase the availability as well as the permanence of this added mineral. Otherwise, lime products often need annual reapplication.

    As to quantities, I remember Andersen talking about no more than 500 pounds of a lime product (somewhat equivalent to oyster shell I think) per acre at one time. I think this is very roughly a pound per 100 sq. ft., not much at all compared to normal liming rates. This shouldn't really upset your pH, Arden mentioned that calcium doesn't do that much to pH compared to magnesium, potassium and sodium. He's actually seen pH drop after application of calcium, probably thru replacement of more alkaline elements.

    The gypsum question might revolve around the sulphate content, which will always have some depressing effect on many microbes (sulphur is a natural fungicide). Also some gypsum is artificially produced, tho most available up here is naturally mined and therefore acceptable for certified organic input. I would only use a bit of gypsum along with other calcium sources...but I am always tempted to include some because sulphur can easily become deficient in my high rainfall climate.

    Glen
     
  6. moondreamer

    moondreamer Member

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    Thanks for all the info. A little sulphur can't hurt here either. Lots of oaks around here tend to make things a little on the alkaline side. Now I can add the calcium in peace of mind, knowing I'm not going to over-do.
     
  7. Ralph Walton

    Ralph Walton Active Member 10 Years

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    Two years ago I applied 2 tonnes (4400 lbs) per acre to our pastures and hay fields. The product was referred to as "rock" lime and I believe it is a waste product from crushing limestone for gravel and/or in the making of cement. It is a very fine powder (don't apply with even the lightest of breezes) and the folks from the soil testing lab indicated this would last for 4 - 6 years. The ideal time for application is before planting and it should be tilled or disked in. This application rate was "moderate".

    Ralph
     

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