7/2/2013 - By Dr. Raymond Snyder

Role:

Phosphorus is the second most essential mineral element required for plant growth.  Phosphorus is required for plant energy metabolism.  In addition, Phosphorus is an integral component of compounds found in plant cells such as sugar-phosphate intermediates of respiration and photosynthesis.  Phosphorus is also vital in the carbohydrate transport system which moves energy to all parts of the plant. Phosphorus is a mobile element within the plant.

Phosphorus influences many turfgrass plant responses.  Phosphorus affects establishment, maturation, and seed production.  In addition, Phosphorus affects color and root development.

Requirement:

Turfgrass generally consists of 0.2 -0.4 % Phosphorus.  Table 1 provides specific Phosphorus sufficiency ranges from leaf analysis for turfgrass.

Table 1.  Sufficiency phosphorus ranges from leaf analysis for selected turfgrass types.

Uptake Sources:

Phosphorus is absorbed by plants in either the H₂PO₄^- or HPO₄^- forms.  In acidic soils, H₂PO₄^- predominates while the HPO₄^- form is present as soil pH increases.  At ideal soil pH levels (5.5-6.5) both forms are found.

Deficiency:

Phosphorus deficiency in turfgass is usually expressed by a darkening of the leaf tissue unlike Nitrogen deficiency where leaves become yellow and pale.  As the deficiency progresses, a reddish purple pigmentation along the leaf blade margins develops.  The purple coloration may be the result of excess anthocyanin production or sugar accumulation.  Older leaves generally are the first to express Phosphorus deficiency.

Phosphorus deficiencies are correctable.  In most cases, adjusting soil pH to levels within the ideal range increases Phosphorus availability such that plant availability is increased enough that a deficiency no longer occurs.  If a deficiency persists, then a granular Phosphorus application may be necessary utilizing Monoammonium Phosphate, Diammonium Phosphate, or Triple superphosphate sources of Phosphorus.