Reme Soilmaster Copyright 1996 -Reme Soilmaster(TM)

POKING ABOUT IN THE DIRT with ROB CUMMING. (Soils Consultant)

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Magnesium:

Soil magnesium is one of those problem areas that is often seen in the Tablelands and Slopes. The soils of.  It can affect legume growth and also grass growth, but is more commonly seen as grass tetne or in some of the milking areas, milk fever.

What symptoms can you see in a clover?

The clover plants often do not grow as well as plants with a correct magnesium balance.  If they are low you have light green leaf colours, for example.

And how do we recognise magnesium deficiencies?

Soil testing is one of the methods for doing this, but it is important not to just test for magnesium on its own, as the amount of calcium is also important. the calcium to magnesium balance is important to obtain correct nutrition in animals.  The higher the calcium to the amount of magnesium in the soil, the more likihood there is of grass tetne occurring in cows.  This factor has been used for many years in assessing the liklihood of grass tetne.

Is it the only factor?

Animal health has never depended on just one single area, as a cow which is becoming stressed can have a very high magnesium need.  If the pasture, which of course is grown on the soil itself, can't supply that need, the stress factor, and in fact the animal's individual genetic makeup also have an effect on the likihood of grass tetne occurring.

But it would be nice if we could isolate the paddocks which had low magnesium, and then when cows which were more prone to be affected by grass tetne could be separated, we would reduce our overall risk for grass tetany.

And what's being done?

This is an area which I have become involved with and I'm working with some veterinary surgeons from the southern part of the state to try and get a much more precise handle or whatever on the ratio of calcium to magnesium in soils related to the liklihood of cows secumbing to grass tetne.

But how long will it take?

That of course, is the sixty- four dollar question.  But how we're approaching it, is to look at paddocks which have had problems and then undertake soil testing on those to check and arrive at a risk factor for those particular soils or paddocks.

I think it's going to take awhile though, to get those sort of estimates but it will certainly provide a very good tool for assessing your risk factor for grass tetany.