Magnesium promotes winter hardiness and early growth. It is essential for nitrogen metabolism and chlorophyll synthesis, and helps the turf to utilise iron and phosphate. Turf which is short of magnesium has yellowing drooping leaves.
Magnesium interacts with both calcium and potassium so should be kept in balance with those. Ideally the calcium to magnesium ratio should be about 10:1.

Function

Magnesium is essential for many plant functions. Some of them are:

  • Photosynthesis: Mg is the central element of the chlorophyll molecule.
  • Carrier of Phosphorus in the plant
  • Magnesium is both an enzyme activator and a constituent of many enzymes
  • Sugar synthesis
  • Starch translocation
  • Plant oil and fat formation
  • Nutrient uptake control
  • Increase Iron utilization
  • Aid nitrogen fixation in legume nodules

Deficiency Symptoms

The classic deficiency symptom is interveinal chlorosis of the lower/older leaves. However, the first symptom is generally a more pale green color that may be more pronounced in the lower/older leaves. In some plants, the leaf margins will curve upward or turn a red-brown to purple in color. Full season symptoms include pre-harvest leaf drop, weakened stalks, and long branched roots. Conifers will exhibit yellowing of the older needles, and in the new growth the lower needles will go yellow before the tip needles.