Magnesium in the soil - Soil Essentials: Managing Your Farm's Primary Asset - page 41

magnesium deficiency are acetonaemia, arthritis, founder, osteoporosis, prolapse
and respiratory ailments. Magnesium in a feed ration may calm hyperactive
animals, and any condition that causes trembling or excessive excitability.
Magnesium is also involved in muscle maintenance and is useful to alleviate or
prevent muscle cramps.

How to address magnesium deficiencies
Magnesium applications to soil should always be based on soil tests because it
should be applied to achieve the desirable ratios with calcium, potassium and
sodium. The soil testing laboratory should give a recommendation for application
rates based on the test results.
There are a number of products that can be used to add magnesium as shown
in Table 8.

Table 8 Magnesium fertilisers

Product % magnesium

Dolomite 10-12

Magnesium oxide 40

Magnesium sulphate 20

Potassium magnesium sulphate 11

Magnesium chloride 11

These products are usually top dressed onto paddocks prior to or just after the
autumn growth commences, or may be spread later in the season if crop
deficiencies or animal health become an issue. There are also foliar spray products
available that are usually based on magnesium chelates. These may be sprayed
directly onto plants as required.
Stock may be given a supplement of dolomite as a loose powder or
incorporated in a stock lick.
For urgent treatment of grass tetany, cattle may be given a subcutaneous
injection of magnesium sulphate or the more modern treatment of powdered
magnesium plus vitamin B 13 tablets placed under the tongue, giving relief in
minutes.