superfosfat

Superfosfat is a group of phosphate-containing fertilizers produced by acidulating phosphate rock to make plant-available phosphorus. The term typically covers two main products: single superphosphate (SSP) and triple superphosphate (TSP).

Production and composition

SSP is produced by treating phosphate rock with sulfuric acid, which yields monocalcium phosphate and calcium sulfate (gypsum). TSP is made by reacting phosphate rock with phosphoric acid, resulting in higher levels of soluble phosphorus and little or no gypsum. As a result, SSP generally contains about 16–20% P2O5 and includes calcium and sulfur, while TSP typically contains around 40–46% P2O5 and is more concentrated.

Characteristics and use

Phosphorus is an essential nutrient for plants, supporting root development, flowering, and energy transfer. SSP and TSP are applied to soils deficient in phosphorus to improve plant growth. SSP also supplies sulfur and calcium, which can benefit soils lacking these nutrients. TSP, being more concentrated, delivers more phosphorus per tonne but can be more difficult to handle and spread consistently.

History and considerations

Superphosphates became widespread with the expansion of chemical fertilizers in the late 19th and early 20th centuries and remain common in many agricultural systems. Care is needed to apply the correct phosphorus rate, since excessive phosphorus can contribute to environmental problems such as water eutrophication. Proper storage and handling are advised, as SSP is relatively hygroscopic and may cake if kept in damp conditions.