Why do leaves turn yellow in case of magnesium deficiency?
Magnesium is essential for optimal plant development, as it is involved in photosynthesis and a number of other plant-internal transport processes. Magnesium is best known for its function as the central chlorophyll atom. Chlorophyll is also known as leaf green.
No chlorophyll, no yield
Chlorophyll is essential for photosynthesis and therefore also for yield formation. An insufficient supply of magnesium will disrupt photosynthetic processes.
Within the plant, magnesium is highly mobile. In case of an insufficient magnesium supply, the plant will transfer this nutrient from older to younger leaves, in order to ensure healthy shoot growth. Within older leaves, magnesium is transported from the leaf's interstitial areas to the veins, resulting in a reduction of leaf green concentration and yellowing of the areas between leaf veins. This creates a marbled appearance, which is considered a typical symptom of magnesium deficiency.
Foliar application as an emergency measure
In general, plants rely on their root systems for taking up nutrients, which is why a balanced nutrient supply via soil is essential. In case of an acute deficiency or in times of peak demand, foliar application of potassium (K), magnesium (Mg) and sulphur (S) may be advisable.