Earth Power – SSP

Single superphosphate (SSP) pioneered the commercial mineral fertilizer industry, marking the beginning of modern plant nutrient development. While it was once the prevalent fertilizer, its usage has diminished compared to other phosphorus (P) fertilizers due to its comparatively lower P content.

Production

The inception of the modern fertilizer industry occurred in the 1840s when it was discovered that the introduction of sulfuric acid to naturally occurring phosphate yielded an excellent soluble fertilizer known as “superphosphate.” Initially employing ground animal bones in this process, the limited bone supply was soon replaced by natural deposits of rock phosphate (apatite). The production of Single Super Phosphate (SSP) closely mirrors the natural occurrence with bones or apatite in acid soils. The fundamental technique has seen minimal change over the past century. Ground phosphate rock reacts with sulfuric acid to form a semi-solid, which undergoes cooling in a den for several hours. This plastic-like substance is then transported to a storage pile for additional curing over several weeks. After hardening, the material is milled, screened to the appropriate particle size, or granulated. The chemical reaction involved is represented as Ca₃(PO₄)₂ [rock phosphate] + 2 H₂SO₄ [sulfuric acid] → Ca(H₂PO4)₂ [monocalcium phosphate] + 2 CaSO₄ [gypsum].

SSP can easily be produced on a small scale to meet regional needs. Since SSP contains both monocalcium phosphate (MCP, also called calcium dihydrogen phosphate) and gypsum, no problems arise with phosphogypsum byproduct disposal unlike the manufacture of other common P fertilizers.

SSP is also known as ordinary superphosphate and normal superphosphate. It’s sometimes confused with triple superphosphate (TSP) production, which results from reacting rock phosphate with phosphoric acid.

Agricultural use

SSP stands out as an effective provider of three essential plant nutrients. The phosphorus (P) component exhibits a soil reaction akin to other soluble fertilizers.

The inclusion of both phosphorus (P) and sulfur (S) in SSP presents an agronomic advantage, especially in situations where deficiencies exist for both nutrients. Demonstrated superiority of SSP over other phosphorus (P) fertilizers in agronomic studies is often attributed to the sulfur (S), calcium (Ca), or a combination of both present in SSP. In regions where SSP is locally available, it has become widely utilized for fertilizing pastures characterized by low levels of both phosphorus (P) and sulfur (S). While SSP excels as a dual nutrient source, it tends to be relatively more expensive as a phosphorus (P) source alone compared to more concentrated fertilizers, contributing to a decline in its popularity.