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Too much calcium & magnesium

Posted by kayemdee 4b (My Page) on
Tue, Apr 21, 09 at 14:05

I've had a lot of problems the last few years with my tomatoes rotting on the vine. The leaves yellow and drop off early, etc. I've grown mainly heirlooms (Brandywine, Cherokee Purple, Sweet Million), but even tried a disease-resistant variety with no better results. I do not grow them where tomatoes or peppers were grown the prior season. Wondered if I had too little calcium.

So, sent off a soil sample to the Extension service and got the following results:

pH 7.6, silty soil
N says to add .30 lb/100 sq. ft.
P 126 (25-40 sufficient)
K 107 (120-180 sufficient)
Calcium 3031 (601-1000 optimum)
Magnesium 545 (101-500 optimum)
organic matter 7.5%

I am mystified by the high calcium. Last spring I put some well-rotted sheep manure/straw on the garden for the first time. That was the only fertilizer I used.

Any suggestions? How do I correct the high calcium? Thanks!

Follow-Up Postings:

RE: Too much calcium & magnesium

It's an element that is ok if it's off the charts. The plant will only use what it needs. You pH is sounds too high.

RE: Too much calcium & magnesium

  • Posted by anney Georgia 8 (My Page) on
    Tue, Apr 21, 09 at 16:25

The optimum pH for most vegetables is 5.8-6.5, so you're over the line a bit. The discussion linked below should give you some ideas about what to do. Just don't add lime to try to bring it down since your calcium measure is so high.

Your tomato problems may not be related to your soil. It could be disease of some kind. If it happens again this year, show us a picture and maybe we can help some. Or take a sample to your Extension office -- they can probably look at it and say what's wrong.

Here is a link that might be useful: My soil pH is too high


  • Posted by anney Georgia 8 (My Page) on
    Tue, Apr 21, 09 at 16:39

Drat, I ALWAYS get it backwards if I rely on my memory. Lime INCREASES soil pH, doesn't decrease it, so you wouldn't add it to bring the pH down anyway.

RE: Too much calcium & magnesium

If you have calcium deficient soil you most likely will see blossom end rot with the first few large tomatoes of the year. I have grown great tomatoes in soil with a pH of 7.5, so im not sure that is a huge problem. To make your soil more acidic (lower the pH), you can add coffee grounds, aluminum sulfate, or magnesium sulfate. It will takes months for your soil to change significantly. Avoid adding ashes and lime. You may want to take pictures,plants, pull a plant and check the roots to rule out a non-soil problem. Your organic content looks great.
If these sheep are raised on alfalfa hay their manure may be the source of the calcium(which is fine).

RE: Too much calcium & magnesium

Hi kayemdee,
Last years animal bedding was probably a lot of urea Nitrogen; that N has been used up.
Urea breakdown can raise the soil's pH ; H+ ions are now needed.
With urea there is usually good Calcium absorption.
High pH may cause decreased absorption of Copper, Zinc & Iron utilization.
Your previous season yellow leaves were possibly more symptomatic of Iron deficiency, than a soil Nitrogen deficit seen this year.
The trace minerals Copper & Zinc together are vital parts of a molecule that is a growth factor regulator; the fruit rotting on the vine may be developmental failure.

RE: Too much calcium & magnesium

Glad to hear excess calcium is OK. Not sure what the sheep ate. Yes, I wish I'd taken pics! The tomatoes rotted mainly when red but, towards the end of summer, some even had a large brownish-yellow soft spot when green. Very discouraging.

I should also say that I've been getting what I think is blossom end rot on my zucchini as well (lots of squash bugs too). The leaves of my pole beans (Purple Podded) get yellow, turn brown and fall off probably a month prior to our first frost. I attributed a lot of that to Japanese Beetles which appeared a few years ago, but perhaps not. Beets, Pumpkins, Lettuce, Cucumbers, Peppers, Chard, are all unaffected.

RE: Too much calcium & magnesium

Hi kayemdee,
Your previous growing season soil conditions are not necessarily exactly what this years analysis is.
The 3 fold level of calcium analysis means your ground has a lot of it.
It is not what the sheep ate that is of interest.
The form of nitrogen called urea is broken down in the soil and in the process you get an ammonia nitrogen the plants can use & also stray carbon atoms.
The plentiful calcium ions in your soil can then bind the newly available carbon to form a molecule that contributes to raise the pH; similar to what adding lime to the soil does.
(Ammonia's pH itself is 11.6.)
In retrospect, your pH during the last growing season may have been higher than recently measured because of the urea that was used around that time.
(To the forum readers in general:
(In most soils the ammonia concentration from urea becomes volatile so some vaporizes up. This makes the soil surface (pH go down & is a factor in long term acidic problem.
( In fact, many agricultural teachings are that urea acidifies the soil, dropping the pH. In hydroponics some use urea (based fertilizer to drop pH in their nutrient solution at the ratio of 1 Tbs Miracle G./20 gallons.
( However, in published research you will find the axiom that urea causes pH to rise; so they study what to do.)
So kayemdee, all this by way of explaining that you should review the type of nitrogen fertilizer you have used in the past to see if urea might have been a factor. (Japanese betel damage is different symptoms.)

RE: Too much calcium & magnesium

Oh, that is interesting info gringojay! Thank you. Good to know for the rest of our alkaline yard. So, what is a Nitrogen that is not Urea-based?

I use the square foot gardening method with raised beds, and some years ago mixed up a soil mix from vermiculite, bagged compost, sand, etc. per that book due to our heavy clay soil. There is weed barrier under the beds, so I would be surprised if it is affecting the pH of the bed much...but then I am not an expert.

What did you mean by "H+ ions are now needed" How do I accomplish that?

In previous years I used a 5-10-5 fertilizer (from ammonium sulfate, ammonium phosphate & muriate of potash) before planting, calculating how much to use based on square footage. I then used diluted fish emulsion most of the growing season. Our water is unsoftened city water, which is alkaline due to our bedrock.

RE: Too much calcium & magnesium

Too much Calcium will lock out other micro nutrients like magnesium, and Iron and a macro nutrient Potassium.
Try to folliar feed the plants magnesium (epson salts) and some micronutrient solution. This will solve the problem. Next year add enough soil to cut down on the calcium.
I had this problem too. Took a while to figure it out. But all is good now.

Here is a link that might be useful: gardening info

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