Single superphosphate fertilizer

Normal Superphosphate. From its beginning as the first commercial phosphate fertilizer, normal superphosphate (NSP), also called ordinary or single superphosphate, has continued among the top fertilizers of the world (Fig. 8). Use of normal superphosphate decreased steadily on a percentage basis because of growing production of more concentrated materials, but grew on a P2 s basis to a maximum of 6.7 x 10 t... 

Solid phosphoric fertilizers are available as mono-ammonium phosphate, di-ammonium phosphate, triple superphosphate and single superphosphate additionally, high-grade liquid phosphoric acid is available. 

Ammonium polyphosphate is one of the most often used phosphoric fertilizers (Corbridge, 1980). It was found to be equally effective when compared with single superphosphate and diammonium phosphate for increasing the yields of wheat and maize and for increasing the available phosphorus content in soil during field experiments (Sharma and Singh, 1998). 

The major use of phosphate is to supply phosphorous, one of the three essential plant foods, nitrogen, phosphorus, and potassium. Phosphate rock extraction from its ore, and its subsequent conversion into fertilizer materials and industrial chemicals, is a relatively mature art. Single superphosphate, a mixture of monocalcium monohydrate and gypsum formed by the reaction of sulfuric acid with phosphate rock, has been used as a fertilizer since the mid-1800s. Phosphoric acid, derived by the treatment of phosphate rock with sulfuric acid so as to produce gypsum in a separable form, was manufactured in many locations by batch and countercurrent decantation methods in the 1920s. 

Fig. 24.10. Continuous process for manufacture of single superphosphate.

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. 

Location, soii type, texture, sampiing depth and totai phosphorus concentration of controi sites in these studies are given in Table 11.1. Mineral phosphate fertilizer (with single superphosphate, triple super phosphate, calcium apatite, or rock phosphate) unless stated otherwise. Carbon concentrations from Lehmann etal. (2001a). 

Run-of-Pile (ROP) - Products that are taken from the production piles without undergoing careful control of the particle size. This form of material consists of particles of many different sizes, from very fine powders to coarse, pebble-like particles. Usually the coarse particles are very friable and can be crushed under finger pressure. Typical examples of fertilizers sold as run-of-pile materials are some forms of single superphosphate and monoammonium phosphate. 

Calcium, Mg, and S are. called the secondary nutrients of the macronutrients because they are not as widd deficient as N, P, and K. They may also have been considered secondary in that they are often contained in materials that are applied to supply another nutrient or need. For instance, Ca and Mg are supplied in large amounts in dolomitic limestones that are applied to raise the pH of acidic soils. Similarly, S fertilizers are not usu-ally applied simply as S sources but are secondary to another nutrient, e.g., in P fertilizers such as single superphosphate, or in the N fertilizer ammonium sulfate. One should not be misled by the term secondary -deficiencies of Ca, Mg, or other nutrients can be as serious as more common deficiencies of N, P, K, or S. They can also very severely limit plant growth. 

In addition, since higher analysis fertilizers have largely replaced S-containing single superphosphate and ammonium sulfate, incidental contributions of S to soils are reduced. Sulfur deficiendes are therefore expected to increase, and sulfur-containing fertilizers will probably be needed, particularly in moist tropical areas and especially for legume and vegetable production.. 

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). 

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. 

The use of sulfuric acid in automobile batteries, however, does not account for its production in such vast quantities. The largest single use for sulfuric acid is fertilizers, especially a sulfuric-acid/phosphate-containing-rock mixture called superphosphate. Because phosphorus is a major mineral nutrient needed by plants and because phosphorus is a major component of bones, bone meal was once a commonly used fertilizer. Today, however, phosphate rock, treated with sulfuric acid to become more soluble, can be used, too. 

Fluorine is common in terrestrial environment and is always present in plants, soils and phosphatic fertilizers. As a rule of thumb, the F concentrations in these materials are on the order of 3 x 10°, 3 x 10 and 3 x 10 ppm for plants, soils and phosphatic fertilizers, respectively. Fluorine is a common constituent of rocks and soils. Very common soil minerals, such as biotite, muscovite, and hornblende, may contain as such as several percent of F and, therefore, would seem to be the main source of F in soils. It appears, therefore, that the F content of soils is largely dependent on the mineralogical composition of the soil s inorganic fraction. Phosphatic fertilizers, especially the superphosphates, are perhaps the single most important source of F in agricultural lands. 

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