Phosphorus (P)

Role in plants

Phosphorus is essential for energy transfer (ATP), root development, early establishment, flowering, and seed formation.

Deficiency symptoms

• Stunted growth
• Dark green foliage
• Purpling of stems or leaf undersides
• Poor root development
• Delayed maturity

Toxicity symptoms

• Rare directly
• Induced deficiencies of zinc, iron, and copper
• Excessive root growth at the expense of shoots

Natural sources

• Weathered phosphate rock
• Soil-bound phosphates
• Organic matter mineralisation

Fertiliser sources

• Monoammonium phosphate (MAP)
• Monopotassium phosphate (MKP)
• Triple superphosphate
• Phosphoric acid

Plant uptake forms

• H₂PO₄⁻ (dihydrogen phosphate)
• HPO₄²⁻ (hydrogen phosphate)