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This article in SSSAJ

  1. Vol. 52 No. 6, p. 1606-1611
     
    Received: Jan 29, 1988
    Published: Nov, 1988


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doi:10.2136/sssaj1988.03615995005200060017x

Salt-induced Manganese Solubilization in California Soils

  1. Riaz A. Khattak  and
  2. Wesley M. Jarrell
  1. Dep. of Soil and Environmental Sciences, Univ. of California, Riverside, CA 92521

Abstract

Abstract

The solubility of Mn in soil solution depends on soil pH, redox potential (Eh), amount and type of higher valency Mn oxides, and a variety of organic and inorganic soil constituents. Laboratory experiments were conducted to determine the extent of salt-induced Mn release from a variety of California soils. To investigate the effect of salinity and time of incubation on Mn release, Redding (fine, mixed, thermic Abruptic Durixeralf) clay loam and Hanford (coarse-loamy, mixed, nonacid, thermic Typic Xerorthent) sandy loam soils were saturated with 0, 75, and 150 mol m−3 NaCl-CaCl2 solution (prepared on an isoequivalent basis) and incubated in a glasshouse for 0, 2, 4, 7, and 10 d. The Mn concentration in the soil saturation extract increased 2- to 4-fold with time of incubation at all levels of salt solution and 7- to 16-fold with increasing salt concentrations (ionic strength) at a given incubation time. Increases in [Mn] with time and increases in pH in the nonamended soil suggest reduction of Mn oxides while increases in [Mn] with increasing salt levels implicates the release of Mn into soil solution through reduction of Mn oxides, displacement by Na+ and Ca2+ and/or ligand (Cl) complexation processes. In another experiment, Mn release by NaCl-CaCl2 salinity was investigated in 20 California soils varying in pH, easily reducible Mn (hydroquinone + NH4OAc), total Mn (HF-HNO3-HClO4), and in total C concentrations. These soils were saturated with 0, 37.5, 75.0, 112.5, and 150.0 mol m−3 NaCl-CaCl2 solution and extracted after 5 d of incubation in a glasshouse. Depending upon soil pH, easily reducible and total soil Mn levels, the [Mn] in soil saturation extracts increased from 10 to 4000 mmol m−3 for 150 mol m−3 NaCl-CaCl2 levels over the nonsaline (deionized water) treatments. Although the order of magnitude of salt-induced Mn release was high in soils low in pH and high in easily reducible Mn, a significant salt effect was noted for even high pH (above 7.0) soils. Multiple regression analysis showed that Mn solubility in salt-amended soils was mainly related to soil pH, easily reducible and total Mn (R2 = 0.68***, significant at p < 0.001). This indicates that factors related to geochemical environments in which soils exist might explain the variations in Mn solubility in salt-amended soils.

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