Soil test low Mg

Discussion in 'Planting, growing, nurturing Plants' started by dreuky, Jan 10, 2015.

  1. dreuky

    dreuky Junior Member

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    Hi, Had a soil test done on my new land. It came back as sand over clay over limestone. Not any surprises there. The minerals are all in the correct amounts except for Magnesium which is low making the Ca/Mg ratio wrong. The soil is neutral so the report that came back said not to do anything. I queried adding dolomite to raise the Mg level and was told no because that would make the soil alkaline which would be bad. I can see that but wonder what I should do about the low Mg levels. The soil guy was of the opinion as I am not planning on running breeding cows on the land it doesn't matter. With breeding cows there is a risk of grass tetany which is basically the cow runs out of Mg and if not treated suffers from a bad case of the ups and dies.

    Does anyone have any ideas?
     
  2. andrew curr

    andrew curr Moderator

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  3. dreuky

    dreuky Junior Member

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    Milang South Aus rainfall 350mm/year
     
  4. Bryant RedHawk

    Bryant RedHawk Junior Member

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    magnesium sulfate is the additive to use in neutral to alkaline soils. Dolomite is for acidic soils only as it is alkaline in nature.
     
  5. Curramore1

    Curramore1 Junior Member

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    Maybe just ad lib supplement the cattle with a high Mg lick containing magnesium salts, such as Epsom salts in a Common salt/molasses carrier? You could also boom spray a dilute foliar application of Magnesium sulphate onto your grasses, it is readily soluble in water and will not change the pH of your soil in the minor amounts that you apply to the pasture.
     
  6. dreuky

    dreuky Junior Member

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    If I use Magnesium Sulphate foliar application on the pasture what rate should I be putting it out?
     
  7. Curramore1

    Curramore1 Junior Member

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    Magnesium supplementation.

    Dusting pastures with Magnesium oxide in a granular form is the most common method used to boost pasture Mg levels. "Causmag is about $500/tonne in bulka bags and probably about twice that in 20 kg bags. It is 56% Mg, but insoluble in water and does not work well in alkaline soils, whereas Epsom salts Magnesium sulphate is only 9.6% Mg, is water soluble and can be applied by boom spray at a rate of 10-15g/L combined with 10g/L Calcium nitrate and 100 mL of wetter per 100L. Apply at 200-300L/Ha of this brew in the late spring/early summer. Epsom salts in 25kg bags cost about $20.00.So about $3.50/ha for the Magnesium sulphate. Is straight out magnesium nitrate cheaper to apply? it is $25.00 for 20 kg at 9.4% Magnesium content, so about the same price. it is marketed as Omnimag.
    How low is the Mg reading? Is it limiting plant growth? Are there deficiency symptoms in the pastures? Try a small trial plot and see if it makes a visible difference.
    Personally I would supplement the animals grazing it with a lick made up of a mix of Causmag 6kg+Oats or similar 35kg+2L water+3kg of molasses and add coarse salt until the cow intake is down to about this brew lasting 100 cow days ie. 5 cows 20 days, or 10 cows 10 days, or 20 cows 5 days, instead of a foliar application. The undigested and excreted residue is going back onto the pasture anyway, but will be concentrated at their camps. ( mix it up in a cement mixer). The more salt, the less intake, you could also lower the grain % if they are eating too much. You can buy ready made "causmag" blocks as well, but we don't have the problem here, so I have no experience with them.
    Olsens Beefmaster blocks are 18.6% Magnesium oxide and cost about $2/kg and come in 15kg, 40kg and 100kg blocks. Each adult cow should take in 300g/hd/day to be effective, so a 15kg block would last 10 cows 5 days, a 40kg block 13 days, a 100kg block about a month. Pretty hefty cost at 60cents a head a day. I think that I would make my own.
    I hope I did not create more questions than answers.
     
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  8. andrew curr

    andrew curr Moderator

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    pretty sure there is a mg rumen bolus available for bovine!
     
  9. dreuky

    dreuky Junior Member

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    I don't have cows. This is why I was told not to worry about the low Mg. Breeding cows are most likely to suffer a problem from low Mg. I supplement my horse with MgO anyway, but I felt if the Mg is low it would be a good idea to bring it up even though I don't have cows. What are signs of Mg deficiency in pastures?
     
  10. Curramore1

    Curramore1 Junior Member

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    Hello again dreuky,
    sorry to nod on about cows then, barking up the wrong tree again as per usual. Severe Mg deficiency produces slower grass growth with narrow, spindly leaves which will be yellower than they should be, starting from the base and the leaf veins in broad-leafed plants may stand out a bit greener than the yellow inter-veinal areas. Plant flowering and grass seed set is also affected. Mg is an essential element in the formation of chlorophyll, so you can see that performance would be affected by this.
     
  11. dreuky

    dreuky Junior Member

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    Thanks for the info the plants all seem pretty green to me definitely no difference between veins & intervein areas
     
  12. WAA WAA

    WAA WAA New Member

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    have you looked at other interpretations of soil testing...i don't know a lot about biodynamics but their perspective may be interesting....i think soil minerals is more complex than replacement therapy!
     

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