Needing help re: Adding Calcium in the form of Gypsum to my Soil

felin(8B)May 21, 2010

Hi All,

Tis my first posting here.

My peppers are beginning to fruit and one of them has a black tip on it which after researching sounds as if it may be blossom rot. The only thing that causes me to not be certain that this is actually rot is, the pepper is only black in color on bottom third of pepper, but not actually rotted. Anyhow, assuming for a moment that the problem is, in fact, blossom rot, I see, after more research, that it is likely necessary for me to add some calcium to soil. Our pH is 8.0 and garden organic, therefore, Gypsum seems to be the best choice. ??? What I do not know are these things that perhaps y'all can help me with:

1. How much do I add?

2. Where, exactly, in reference to the plant, do I add it?

3. If I have Tomatoes very near by, should I go ahead and assume that they will likely end up with rot as well and go ahead and amend the soil near them as well?

4. How long will the calcium FROM this Gypsum actually take to get up into the plant? If it takes too long, I am afraid we will lose what we have. So far, we have 6 tomato plants and 6 pepper plants (3 sweet, 3 hot).

Thank you so much in advance!!


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jollyrd(Richmond VA)

wow, pH 8.0 - that must sound great, but I wonder if just a bit high?
anyway, I add gypsum to the root area of tomatoes - literally one handful per plant. I understand that the roots get the gypsum with water - so you need rain or watering down at the soil level (not too much water on the plant)
not sure how long this would last but I plan to add another doze in a month depending on amount of rain we get

    Bookmark   May 21, 2010 at 4:31PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Sounds like you may have gotten into some outdated research on BER. The cause of BER is not necessarily a lack of soil calcium - that has been known for several years, and is well researched and well documented. The problem lies in distrubting that calcium to the fruit. However the old info/claims persist I'm sorry to say and leads too many into trying to fix a problem that doesn't really exist - thereby making the problem worse.

BER is caused by inconsistent distribution of the calcium that does exist in the soil while the fruit if forming. Commercial growers discovered this years ago when they found that the problem of BER persisted even in fields that had been well and regularly amended with calcium.

You'll find a FAQ here (linked it below) with more details but what it often boils down to is watering problems in combination with spring weather patterns.

Inconsistent water supply to the plant, whether in the form of too much or too little or too much rain, etc. often causes BER in the early fruit as the calcium is not distributed evenly to the fruit. As the weather settles, watering patterns are stabilized, and the plant matures and adapts, BER goes away all on its own. Another contributing factor may be too much nitrogen fertilizer.

Few soils will test out as low in calcium but many gardens suffer from inconsistent soil moisture levels. ;) Be patient with your plants and any BER you are seeing now will soon disappear.


Here is a link that might be useful: BER FAQ

    Bookmark   May 21, 2010 at 4:45PM
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Something does not compute here. You can not have a pH of 8.0 and low Ca. Ca is (by far) the dominant alkaline element in soil, high pH soils necessarily have a lot of Ca.

    Bookmark   May 21, 2010 at 7:17PM
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I agree with Dave and glip.

Gypsum is like lime,that raises soil PH. A PH =8 is normally high, anyway.

Also, BER is not a problem with ALL kinds of tomatoes. Last year only my ROMAs had BER, none other.
I think also the weather contributes to that. That is, too much rain or sprinkle watering.
Roting is a bacterial action and bacteria need aquous environment to thrive.

    Bookmark   May 21, 2010 at 8:17PM
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jean001(z8aPortland, OR)

Folklore & common wisdom aside, gypsum pH is about 6.8. It won't change pH up or down.

Gardeners who live in arid parts of California don't need additional calcium in their soil.

who gardened for 30-some years in SoCal

    Bookmark   May 21, 2010 at 9:16PM
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dancinglemons(7B VA)


I do not think there is anything wrong with your peppers. My green bell peppers have dark bottoms - some almost black when they are young and as they grow and mature they turn green all over (then red). You say there is no rot just very very dark bottom. Just a thought..........


    Bookmark   May 22, 2010 at 2:00AM
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jimster(z7a MA)

In my experience blossom end rot affects only some of the early fruit. Later fruit are fine.


    Bookmark   May 22, 2010 at 8:55AM
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Concur with one exception. Calcium has no effect on pH. The base in alkaline soil is the OH radical. Limestone( Calcium carbonate) does neutralize acid because the Carbonate radical reacts with acid. Same type of reaction as Tums in your tummy.Some places will sell calcium hydroxide which is a base and acts fast. Gypsum is Calcium sulphate a neutral salt. I certainly do not recommend it, but the commonly sold Rot Stop is Calcium Chloride also neutral, but I do not want to add chloride ions to my soil.

1 Like    Bookmark   May 22, 2010 at 11:39AM
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Shule(about 4a)

You might consider the following:

* Beneficial microbes (via manure, compost or whatever); these can sometimes help nutrients to be available

* Organic certified potassium sulfate (this should help your plants to be less finicky about water, and may help prevent BER; it may reduce your PH a little, too); additionally, there are many perks to potassium, if your plants aren't getting enough; potassium sulfate is better to use than potassium chloride, since potassium chloride kills beneficial microbes in the soil.

* Loosening or aerating your soil (you could till the ground, attract worms, add perlite, peat moss, cover crops, organic matter or maybe even sand); compact soil can cause issues with potassium and maybe calcium

* Add plain sulfur to make the soil more acidic. This potentially might make your calcium and potassium more available. However, it may take a long time to work. I hear it's easier to raise PH quickly than to lower it quickly. I don't know a lot about adding sulfur. There may be some drawbacks.

    Bookmark   Yesterday at 12:19AM
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