Apparent salt sorption reactions in an unfertilized acid subsoil

R. C. Pearce, M. E. Sumner

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31 Scopus citations


The equivalent retention of Ca2+ and SO4/2- from gypsom solutions in acid subsoils has recently been reported. The term salt sorption has been coined to describe this process, yet little known about the nature of the reactions involved. This study was conducted to determine if other cation-anion combinations would exhibit similar and to examine the extractability of the sorbed ions. An unfertilized acid Cecil (clayey, kaolinitic, thermic Typic Kanhapludult) subsoil was equilibrated using a saturated paste technique with solutions of six different salts at a loading rate of ≃14.0 nmol(c) kg-1. The solutions were CaSO4 MgSO4, Na2SO4 CaCl2, MgCl2, and a deionized water control. This soil exhibit salt sorption with all six electrolyte solutions. The SO4 salts were almost completely sorbed both cation and anion uptake on the order 13.8 nmol(c), kg-1. Calcium and magnesium chloride were sorbed at ≃11.7 mmol(c) kg-1, and NaCl was sorbed at 8.2 mmol(c) kg-1. The treated soils were air dried and extracted with successive portions of deionized water or 0.5 M NH4NO3. A relatively large proportion of both cations and anions were removed by repeated extractions with water, suggesting that ionic strength played an important role in the salt sorption process. Nearly all of the sorbed cations and Cl- were recovered by neutral salt extraction but <100% of the SO4/2- could accounted for by neutral salt extraction. Neutral sail extractable Al was significantly reduced by salt treatment. It appeared that salt sorption in this soil my have resulted from several mechanisms including precipitation, specific adsorption, ionic strength induced charging amd ion pair adsorption operating concurrently.

Original languageEnglish
Pages (from-to)765-772
Number of pages8
JournalSoil Science Society of America Journal
Issue number3
StatePublished - 1997

ASJC Scopus subject areas

  • Soil Science


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