Overestimation of phosphorus adsorption capacity in reduced soils: An artifact of typical batch adsorption experiments

S. Brand-Klibanski, M. I. Litaor, M. Shenker*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Although soil reduction often results in P release to soil solutions, many researchers have observed an increased maximum P adsorption (Smax) following soil reduction. We hypothesized that this result is an experimental artifact caused by exposure of the reduced soils to aerobic conditions and by the use of high P additions, which may result in precipitation. Four semiarid altered wetland soils were incubated under reduced conditions, followed by reoxidation, and their P-adsorption characteristics were measured under atmospheric and N2-atmosphere conditions. During the reductive incubation, soluble P and Fe concentrations increased. In one of the soils, P and Fe were monitored after reoxidation and both were found to decrease. The reduction-reoxidation cycle has led to increased Smax values. Under an N2 atmosphere, the equilibrium P concentrations at zero adsorption (EPC0) of all soils were higher than those determined under atmospheric conditions, whereas no significant changes were observed in S max values. Oversaturation of the equilibrating solutions with respect to P minerals suggested P precipitation and overestimation of S max at high added P concentrations under both aerobic and N 2-atmosphere conditions. We conclude that aerobic batch experiments of reduced soils are affected by P adsorption to newly in-tube-formed ferric oxides. In accordance, we stress the importance of the EPC0 rather than the Smax as an informative measure of P adsorption, and the need for using low-P experiments and maintaining anaerobic conditions in evaluating P adsorption of reduced soils.

Original languageAmerican English
Pages (from-to)1128-1136
Number of pages9
JournalSoil Science Society of America Journal
Issue number4
StatePublished - Jul 2007


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