superphosphate

Superphosphate is a type of phosphorus fertilizer produced by acidulating phosphate rock with mineral acids to form soluble phosphates that plants can uptake. It has been widely used to supply readily available phosphorus for crops since the 19th century.

Single superphosphate (SSP) is produced by reacting phosphate rock with sulfuric acid. The principal soluble phosphate in SSP is monocalcium phosphate (Ca(H2PO4)2); gypsum (calcium sulfate) is formed as a byproduct. SSP typically contains about 16-20% P2O5 and is moderately acidic, with some sulfur and calcium.

Triple superphosphate (TSP) is produced by reacting phosphate rock with phosphoric acid, yielding a more concentrated soluble phosphate with negligible gypsum byproduct. TSP usually contains around 44-46% P2O5 and is more acidic than SSP, making it a stronger direct source of phosphate for soil.

Uses and agronomy: Both SSP and TSP are applied to soils to correct phosphate deficiency and improve root development, flowering, and yield in various crops. SSP is often used in blended fertilizers and in regions where inexpensive phosphate sources are needed; TSP is used where higher immediate phosphate availability is required.

Environmental and safety considerations: The manufacture and use of superphosphates involve handling acids and phosphates, and the production generates gypsum waste. Phosphorus runoff from fields can contribute to eutrophication; proper application timing, rate, and incorporation into soil are recommended. SSP can acidify soils somewhat; TSP is more acidic and may influence soil pH more strongly.