Magnesium: Functions, Deficiency, Toxicity and Corrective Measures–A Review

Abstract

Magnesium (Mg) is an essential secondary macronutrient that contributes to numerous structural, physiological, and biochemical processes in plants. This review examines the major functions of Mg in plant nutrition, the causes and consequences of Mg deficiency and excessive Mg supply, and the principal approaches used for corrective management. Magnesium is central to chlorophyll structure and is involved in photosynthesis, energy transfer, enzyme activation, protein and nucleic acid synthesis, carbohydrate metabolism, phloem loading, assimilate translocation, and ionic regulation. Deficiency commonly develops in acidic, coarse-textured, highly weathered, or intensively cultivated soils where Mg reserves are limited or losses through leaching and crop removal are substantial. Nutrient imbalance, particularly excessive potassium supply, may further restrict Mg uptake. Characteristic deficiency symptoms include interveinal chlorosis of older leaves, followed by progressive chlorosis, necrosis, premature senescence, impaired photosynthesis, disturbed carbohydrate partitioning, and reductions in crop growth and productivity. Excessive Mg is less frequent and primarily causes problems through antagonistic interactions with calcium and potassium and through unfavourable cation balance. Appropriate management therefore requires soil and plant diagnosis, balanced fertilisation, suitable Mg-containing amendments, correction of soil acidity, organic inputs, foliar supplementation where appropriate, and careful management of interacting nutrients. An integrated diagnostic approach can support adequate Mg nutrition while avoiding unnecessary nutrient application.