As you can see from the NRM News article dated 27 September 2010, approx 65% of samples revealed a greater than target % for Magnesium (Mg) in Grassland. Excessive magnesium will constrain air and water pores in the soil and nutrient lock up is likely to result, particularly N and K. It is a topic that is not referred to very often but is all part of the management of nutrient balance so important to farm profits.
The solution is Calcium Sulphate. This will have the effect of aerating and conditioning the soil, especially heavy clays and releasing the Mg.
For an immediate short term solution use Granular Calcium Sulphate 39CaO 55SO3
It is important to only use this product as the solubility of the product will give a fast response. A spring application is an effective method of applying Sulphur.
A slower acting, quarried product is available for longer term effects. You may choose this approach if the land is not rented and you will gain the benefits at a lower cost.
Guard against waste products such as gypsum as these products may not be efficient in an agricultural environment.
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