phosphorus

Symbol: P. A nonmetallic element, atomic number 15, atomic weight 30.9, important as a macronutrient for plant growth. It is essential for the formation of nucleic acids, lipoproteins, and energy-carrying molecules and is involved in many aspects of metabolism, especially carbohydrate metabolism. Phosphorus occurs in soil minerals as the apatites and as calcium phosphate rock. It is absorbed by roots as the P0₄^3- ion, this ion acting as an important buffer in the cell sap. Deficiency results in poor root growth, bluish, bronzed, or purple leaves, and poor germination, ripening, and seed set. Phosphorus can be applied to soils as inorganic basic slag or superphosphate or in various organic materials, guano and bonemeal containing a particularly high percentage. It is often applied in combination with nitrogen and potash in compound fertilizers.