Magnesium

A major plant nutrient, which is represented by the chemical symbol Mg. It typically forms the fifth highest percentage of any plant nutrient (excluding carbon, hydrogen and oxygen) within a turfgrass leaf, with a typical dry matter mid-range concentration being around 0.2%.

It is involved with photosynthesis, forming part of the chlorophyll molecule and therefore is essential for producing a green turf. It is an essential contributor to the synthesis of ATP, improves the efficiency of enzyme reactions and regulation, as well as cell pH regulation and helps maintains a suitable balance between anions and cations within a plant.

High concentrations of magnesium, especially during prolonged dry periods, can reduce and inhibit photosynthesis, potentially reducing recovery times coming out of the dry spell. However, phosphorus uptake can be increased with high concentrations of magnesium, so where a good root system exists, the plant may be compensating for reduced current photosynthesis by building some nutrient reserves ready to take advantage of when weather conditions improve.

Magnesium deficiency results in reduced photosynthetic activity and consequent formation of carbohydrates. In addition, chlorosis occurs, with the uptake of the nutrient being negatively affected by highly acidic soils and high concentrations of potassium and ammonium. The leaf margins of mature leaves also turn a dark reddish colour when deficiency initially occurs.

There is usually an adequate amount of magnesium within most soils; although there may be a need to apply small amounts of this nutrient where it has been leached from a free draining soil.