Single Superphosphate SSP

Single superphosphate (SSP), also called normal or ordinairy superphosphate, has been the principal phosphate fertilizer for more than a century and supplied over 60% of the world s phosphate as late as 1955. Since then its relative importance has declined steadily. In 1975, it supplied only 20% of the phosphate fertilizer, and this figure fell to 17% in 1988. The decline in actual tonnage has been small, but most of the new facilities have been built to produce other, higher analysis products. For the world as a whole, TVA estimated 1972 SSP production at 7,87 million tonnes of P2O5 and IFDC mentions a figure of 7.083 million tonnes in 1988, which means a decrease of 10% over 16 years [1). 

Another decrease of 10% reduced the production to 6.3 million tonnes in 1992, which was about 16% of the 38.6 million tonnes of P2O5 produced in 1991/92. Tlius, SSP is still an important phosphate fertilizer and is likely to remain so even though its relative importance will decrease. 

The process is simple, requiring little technical skill and small capital investment, 

The economies of scale are minor thus, small plants can be economical. 

Since the process is not capital intensive, there is little advantage of a high percentage utilization of capacity. In fact, many SSP plants operate on a planned seasonal schedule. 

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Zhu et al. (2004) evaluated the effectiveness of treating a Pb-contaminated alkaline soil with hydroxyapatite (HA), phosphate rock (PR), water-soluble P fertilizer (single superphosphate, SSP), and a combination of HA with SSP by measuring the bioavailability of Pb to Brassica campetris L. var. communis and Brassica oleracea L. var. acephala. The results indicated that the Pb concentrations in both the shoots and roots of the two vegetable plants decreased with increasing quantities of added P compounds. In addition, the HA treatment was most effective at 5 g of P kg compared with other treatments, where the Pb concentrations in shoots and roots decreased by an average of 60% compared to the control. However, the SSP treatment had little effect on the Pb concentrations in plant tissues. 

The manufacture of TSP is quite similar to that of single superphosphate (SSP) and has the same advantages of simplicity, low technical skill requirement, and small capital investment. 

The European Council Directive 76 / 116 / EZC indicates that single superphosphate must contain at least 16% of P2O5 soluble in neutral ammonium citrate of which at least 93% is water soluble. SSP may be either powder form for use as a raw material in the manufacture of compound fertilizers or for application by the farmer, or granular (2-4 mm) for use as a raw material in a bulk blending operation or for application. SSP may be shipped in bulk and in bags, provided it is protected from moisture. 

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