Single super phosphate is

Single super phosphate is a water soluble fertilizer.
Single superphosphate (SSP) was the first commercial mineral fertilizer, and it led to the development of the modern plant nutrient industry. This material was once the most commonly used fertilizer, but other phosphorus (P) fertilizers have largely replaced SSP because of its relatively low P content.
SSP is the only Sulphur providing fertilizer in India which contains water soluble phosphorus easily taken up by plants.