Role in the plant: The outstanding role of magnesium in plant nutrition is as a constituent of the chlorophyll molecule. As a carrier, it is also involved in numerous enzyme reactions as an effective activator, in which it is closely associated with energy-supplying phosphorus compounds.
Deficiency symptoms: Yellowing between the veins of the older leaves of the plant. According to Yara International, the green area of the leaf can form an arrowhead in woody plants. Reddening may also occur around the yellow zone. Leaves may also be abnormally thin.
Toxicity symptoms: not known
Soils that have magnesium most prevalent: soils with high levels of organic matter, or that are limed frequently with dolomitic lime.
Management remarks: High levels of calcium, ammonium and potassium can suppress the availability of magnesium. Consult an agronomist or soil scientist to determine the most suitable ratios between each element.