Experimental data on the phosphate release and sorption in soils, when inadequately described by a first‐order kinetic reaction, are often interpreted as a combination of two or three simultaneous first‐order reactions. A simple modified Elovich equation in the form: q = (1/β) ln (αβ) + (1/β) ln t was derived to fit the reported experimental data in literature that failed to conform to a single first‐order kinetic equation. In this equation, q is the amount of phosphate released or sorbed, and α and β are constants. The equation successfully described the data as a single straight line that covers the entire course of reaction time. It also appears that constants of α and β may be used for comparison of reaction rates of phosphate release or sorption in different soils.

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This review discusses and summarizes the latest reports regarding the agronomic utilization and potential environmental effects of different types of phosphate (P) fertilizers that vary in solubility. The agronomic effectiveness of P fertilizer can be influenced by the following factors: (1) water and citrate solubility; (2) chemical composition of solid watersoluble P (WSP) fertilizers; (3) fluid and solid forms of WSP fertilizers; and (4) chemical reactions of P fertilizers in soils. Non-conventional P fertilizers are compared with WSP fertilizers in terms of P use efficiency in crop production. Non-conventional P fertilizers include directly applied phosphate rock (PR), partially acidulated PR (PAPR), and compacted mixtures of PR and WSP. The potential impacts of the use of P fertilizers from both conventional (fully acidulated) and non-conventional sources are discussed in terms of (1) contamination of soils and plants with toxic heavy metals, such as cadmium (Cd), and (2) the contribution of P runoff to eutrophication. Best practices of integrated nutrient management should be implemented when applying P fertilizers to different cropping systems. The ideal management system will use appropriate sources, application rates, timing, and placement in consideration of soil properties. The goal of P fertilizer use should be to optimize crop production without causing environmental problems.

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