Phosphorus (P) is an essential macronutrient that all plants need in relatively large quantities. The amount of P fertilizer needed by turfgrass is usually significantly less than nitrogen or potassium. However, P is particularly important during early grass seedling growth and development stages. Phosphorus plays a role in establishment, rooting, maturation, growth, and reproduction of plants. Plants can extract the relatively immobile soil P as dihydrogen phosphate (H2PO4-) or hydrogen phosphate (HPO4-2). The terms available phosphate, available phosphorus, available phosphoric acid, and P2O5 may be used to refer to phosphorus fertilization.