Magnesium is an essential element for all plants. Soluble magnesium (Mg) exists in soils primarily as Mg2+, a positively charged divalent cation. Kentucky soils are naturally high in Mg and, thus, Mg applications to turfgrass are normally unnecessary. However, turfgrasses grown in sand-based rootzones, such as golf course putting greens and sand-based sports fields, are prone to Mg deficiency. When Mg is necessary, it is essential to understand the function of Mg in the plant, the dynamics of Mg in the soil, and the forms of Mg fertilizers.