Fertilizer research

, Volume 24, Issue 3, pp 149–157 | Cite as

A discussion of the methods for comparing the relative effectiveness of phosphate fertilizers varying in solubility

  • S. H. Chien
  • P. W. G. Sale
  • D. K. Friesen


Because various phosphate (P) fertilizers differ widely in their solubility, it is commonly observed that crop response to P fertilizers varies under the same soil and crop conditions. Furthermore, a major problem encountered in the methods for determining the relative effectiveness (RE) of water-insoluble P fertilizer (e.g., phosphate rock) with respect to water-soluble P fertilizers, e.g., single superphosphate (SSP) and triple superphosphate (TSP), is that their growth response curves are usually nonlinear and often do not share a common maximum yield. In this paper, we review and discuss the advantages and disadvantages of the three most commonly used methods for calculating the RE of phosphate rock with respect to TSP (or SSP). The three methods are vertical comparison, horizontal (substitution rate) comparison, and linear-response comparison.

Key words

Phosphate rock SSP TSP partially acidulated phosphate rock relative effectiveness (RE) index substitution rate (SR) 


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Copyright information

© Kluwer Academic Publishers 1990

Authors and Affiliations

  • S. H. Chien
    • 1
  • P. W. G. Sale
    • 2
  • D. K. Friesen
    • 1
  1. 1.Agro-Economic Division, IFDCMuscle ShoalsUSA
  2. 2.School of AgricultureLa Trobe UniversityBundooraAustralia

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