Estimating soil phosphorus sorption saturation from Mehlich-3 data

Peter J.A. Kleinman, Andrew N. Sharpley

Research output: Contribution to journalArticlepeer-review

116 Scopus citations


Soil phosphorus sorption saturation (Psat) measures the degree to which soil phosphorus (P) sorption sites have been filled and has been found to be a good indicator of P availability to runoff and leachate. At present, analytical methods required to estimate Psat are generally not offered by soil testing laboratories. This study evaluated the use of Mehlich-3 data in estimating Psat in a wide range of soils. In acidic soils (pH = 4.1-5.9), Psat estimated from Mehlich-3 P, iron (Fe), and aluminum (Al) was highly correlated with Psat estimated from ammonium oxalate data (r = 0.94) as well as with a reference Psat estimated from bicarbonate P and the Langmuir sorption maximum (r = 0.89). In alkaline soils (pH = 7.3-8.4), Psat estimated with Mehlich-3 P and calcium (Ca) was highly correlated with the reference Psat (r = 0.84), and the strength of that correlation improved only slightly by factoring in soil clay content (r = 0.86). Results indicate that Psat may be effectively estimated from Mehlich-3 data across a wide range of soils. This study confirms that Psat may be readily estimated by soil testing laboratories that routinely measure Mehlich-3 P, Al, Fe, and Ca.

Original languageEnglish (US)
Pages (from-to)1825-1839
Number of pages15
JournalCommunications in Soil Science and Plant Analysis
Issue number11-12
StatePublished - 2002

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Soil Science


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