How much epsom salts for magnesium deficiency with blueberries?

sharppa(6)May 22, 2013

I did a soil test recently for 30 blueberry bushes in a 25 x 50 foot bed. Magnesium was quite low and they suggested 1270 lbs/acre of Epsom Salts so 35 lbs of Epsom Salts for this smaller area. Somehow that seems like a lot to spread all at once? Older postings talk about 1/4 cup per plant or a few tablespoons mixed with water. What do people suggest?

Soil test said:

pH: 4.2 (a little too much sulfur last year I guess)

Plant Nutrient Needs:

Phosphate 50 lb/A
Potash 110 lb/A
Magnesium 140 lb/A (or 1270 of Epsom Salts, 280 of Magox)

The majority of these plants were bare root planted last year and are doing okay. Some new growth last year with some holly tone early last year and one dose of Miracid last summer. This year they have had one dose of Miracid about a month ago which was after the soil test.

I'm planning two more doses of Miracid (soon and in a month) and the Epsom Salts and maybe some greensand to help with the potash deficiency.

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beeman_gardener(5)

With such a low Ph I would go easy on the acid additions.
As to the Epsom salts, something is horribly wrong, far too much suggested.
Would suggest no more than 1 tablespoon per gallon.

    Bookmark   May 22, 2013 at 7:46PM
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sharppa(6)

Thanks for the reply.

I've attached the soil test results for this blueberry patch from Penn State.

Exchangeable Cations for Mg is 0.5
% Saturation of the CEC for Mg is 3.1

I did two other soil tests in other parts of my property with different soil types. One area that is a vegetable garden that I limed and fertilized with Garden Tone last year. It's MG numbers are 1.8 and 18.4 and the Mg is a little high. The test says pH is 6.9 an I need 1.75 lbs of 10-10-10 per 100 square feet.

The other area is old farm fields that are mostly clay and worn out. The Mg numbers there are 1.1 and 11.4. No amendments yet for that area. Soil test says 5 lbs/100 square foot of Calcitic Limestone plus 3.5 lbs of 10-10-10 plus 0.5 lbs of 0-46-0.

    Bookmark   May 22, 2013 at 8:42PM
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shazaam(NC 7B)

In terms of the amount of Mg to add and the amount of epsom salt required to reach that amount, the numbers seem reasonable. Nonetheless, I can understand your caution. Perhaps you should ask this question in the Soil forum -- there are some very smart people there who know a lot about soil science. As a side note, you might want to consider langbeinite as an alternative to epsom salt. It's a good source of magnesium and potassium. That would kill two birds with one stone...

    Bookmark   May 22, 2013 at 10:32PM
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