What do you need to remember to ensure your crops get the right amount of magnesium at the right time?

Magnesium may be classed as a secondary nutrient when compared to N, P and K, but most potato, sugar beet and vegetable growers appreciate the vital role it plays in yield optimisation. And as many soils show a gradual decline in magnesium levels, farmers of combinable crops are beginning to take magnesium just as seriously.

A lack of magnesium will limit yield potential


Magnesium deficiency in wheat

As an essential nutrient, we know that optimum growth cannot be achieved without an adequate supply of magnesium. As the central atom in chlorophyll, magnesium is crucial for efficient photosynthesis and therefore low levels in the leaf will have a direct impact on yield. It is also required for the production of starch and sugars, their movement in the plant and for seed fill. In addition to these functions, magnesium, by stabilising cell membranes and regulating calcium movement, helps reduce plant susceptibility to disease.

Soil testing is useful but may not give the full picture

Soil analysis will measure overall levels of magnesium but as your agronomist will tell you:

even soils that meet target indices may still suffer from low availability of magnesium precisely when the crop needs it most.

Field conditions can restrict magnesium availability

Magnesium deficiencies are generally more prevalent in light, sandy and calcareous soils and soils with a low pH. High levels of soil calcium and potassium can also limit availability and uptake, as they displace magnesium ions from root accessible sites in the soil matrix.
Even without the impact of adverse soil chemistry, uptake can be affected by cold and dry conditions and if this coincides with high crop demand, deficiency problems can readily occur. Visible symptoms normally appear on older leaves first, as chlorosis or yellow marbling between the leaf veins, spreading from the leaf tips and margins.

Soil application can be problematic

Although soil-applied magnesium supplements offer solutions for building up soil reserves over the longer term, they cannot be relied upon to deliver adequate supplies when soil chemistry and growing conditions limit availability. Poor root development in some crops can also restrict access to magnesium supplies. For these reasons, many growers use leaf applied nutrition to ensure availability at times of peak crop demand or during periods of adverse growing conditions.

Formulation is key to efficiency in foliar feeds

Developments in foliar magnesium treatments

Developments in foliar magnesium treatments

Foliar feeding of magnesium has traditionally been carried out by using Epsom salts a bulky, bagged crystalline solid requiring relatively high application rates. Concentrated liquid formulations are a good alternative if you are looking to reduce application rates and tank mix preparation times. Alternatively, Magnesium can be applied in combination with other key elements including phosphorus, potassium and sulphur with advanced formulations using biostimulant technology to increase the efficiency of uptake and delivery and reduce application rates even further.

Ilex Foliar Applied Magnesium Supplements

Ilex-Mag-Plus-MagnesiumMag Plus is a fully water soluble high concentration liquid. Its enhanced formulation of soluble Magnesium with Nitrogen gives more immediate plant availability and superior performance at low application rates.
Mag Plus is recommended for application at rates of 2-4l/ha on combinable crops and 3-5 l/ha on potatoes, brassicas and root crops.



Magiphos takes a different approach. Using phosphite chemistry it increases the mobility and uptake of magnesium. It is a fully water soluble solution for ease of use and combines magnesium with sulphur, phosphorus and potassium to boost health, vigour and yield potential. Its zero-nitrogen formulation allows for unrestricted application for all crops.
Magiphos is recommended for application at rates of 1.5-2.5 l/ha on combinable crops and 2-3 l/ha on potatoes, brassicas and root crops.

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