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Magnesium (Mg), is a plant essential nutrient important for photosynthesis and preventing hypomagnesemia (grassland staggers) in livestock.

Essential nutrient contributing to 0.1-0.5% of a plants nutritional makeup

Aids in the use and transportation of phosphorous and is a key component of chlorophyll

Deficiency symptoms include yellowing between veins of older leaves

Magnesium losses are minimal due to its ability to bind to clay soil particles

Best applied to the soil at crop establishment to proactively prevent magnessium deficiency

Magnesium containing fertilisers include Wolftrax Magnesium and ESTA Kieserite (15%)



Magnesium is involved in the formation of chlorophyll - the compound by which plants photosynthesise - and so is key for plant growth and sugar production.

Magnesium also acts as a 'phosphorus carrier' in plants - a function which is necessary for protein formation and cell division. Magnesium needs to be present for phosphorous uptake to take place, therefore magnesium is essential for phosphate metabolism, plant respiration and the activation of several enzymes.


Within livestock, magnesium helps facilitate several chemical reactions which provide animals with energy to move and grow. It is also involved in the transmission of nerve pulses.

High levels of potassium within an animals diet can reduce magnesium absorption into the blood, which can lead to hypomagnesemia (staggers) and sudden death if left untreated.

Ensuring animals consume sufficient levels of sodium within their diet can help mitigate this risk as sodium helps improve magnesium absorption into the blood.

The critical ratios of potassium:sodium and potassium:magnesium within grass or forage are less than 20:1 and ideally less than 10:1 in order to minimise the risk of staggers.



Like calcium and other positively charges nutrients, magnesium (Mg2+) is able to bind to negatively charged clay particles within the soil. Because magnesium is a much smaller ion than calcium (Ca2+), soils with a high magnesium:calcium ratio tend to be tighter with poorer structure. This can make high magnesium soils difficult to work.

In these soils, opportunities should be taken to add calcium into the system.


Magnesium causes leaves to turn yellow between veins, giving them a mottled appearance.  

As magnesium is fairly mobile within the plant, deficiency symptoms appear on the older leaves first. 

In potatoes, magnesium deficiency results in black necrotic blotches.

Where is the risk of deficiency highest?
  • Cold, wet soils
  • Light, sandy soils with low organic matter content
  • Low pH

A standard (S) soil analysis can help determine the quantity of magnesium which is likely to be available for crop uptake and can be used to help tailor fertiliser plans and to help deficiencies within the season. 

Tissue testing is also useful to determine the magnesium concentration of the plant mid-season in order to compare against optimum levels. Although laboratory results may be available too late to correct the deficiency in the current crop, they can be useful for decisions on magnesium use for future crops.

Blood tests on livestock can help indicate whether there is a magnesium deficiency within the grass or forage. 

Loss Pathways

Magnesium is less prone to leaching losses due to its positive charge and its ability to bind to clay particles. Losses will be greater in soils with a low clay content. 

Right Product

Coating fertiliser granules with Wolf Trax magnesium means that there are around 50 more landing sites in comparison to the granular alternative, resulting in greater plant uptake. 

Improving soil magnesium levels is better achieved using granular products. Where magnesium deficiency is likely, highly soluble products may be most appropriate.

Right Time

In arable situations, applying magnesium at crop establishment proactively prevents magnesium deficiency.

Right Place

Applying magnesium to the foliage is often too late as plants have already lost yield potential. Applying magnesium to the soil during establishment means there is no 'hunger gap'.

Right Rate

Using a Wolf Trax magnesium coating means plant uptake is maximised and so only small rates of magnesium are required.

Contained Within...
ESTA Kieserite20% S + 15% MgHighly soluble magnesium and sulphur fertiliser mined from natural salt deposits. Organic certification
Polysulphate19.2%S + 11.6%K + 3.6%Mg + 12.2%CaA high sulphur multi-nutrient containing sustained release sulphur. Mined from natural rock deposits. Organic certification. Low chloride
Sweetgrass23-0-0 + 2%S + 1.2%Mg + 5%Na Improves grassland palatability and subsequent forage intake, leading to higher milk or meat production where no P or K applications are required
MICRO-MATCH magnesiumN/AA micronised charged powder which coats every granule of fertiliser. Contains both immediate and sustained release nutrition.