Fertilizer research

, Volume 24, Issue 3, pp 149–157

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


  • S. H. Chien
    • Agro-Economic Division, IFDC
  • P. W. G. Sale
    • School of AgricultureLa Trobe University
  • D. K. Friesen
    • Agro-Economic Division, IFDC

DOI: 10.1007/BF01073583

Cite this article as:
Chien, S.H., Sale, P.W.G. & Friesen, D.K. Fertilizer Research (1990) 24: 149. doi:10.1007/BF01073583


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 rockSSPTSPpartially acidulated phosphate rockrelative effectiveness (RE) indexsubstitution rate (SR)

Copyright information

© Kluwer Academic Publishers 1990