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Dissolution of Phosphate in a Phosphorus‐Enriched Ultisol as Affected by Microbial Reduction
Author(s) -
Hutchison Kimberly J.,
Hesterberg Dean
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.1793
Subject(s) - dissolution , ultisol , chemistry , phosphorus , dissolved organic carbon , environmental chemistry , loam , soil water , phosphate , organic matter , redox , inorganic chemistry , soil science , geology , organic chemistry
Phosphorus dissolution often increases as soils become more reduced, but the mechanisms are not fully understood. The objectives of this research were to determine rates and mechanisms of P dissolution during microbial reduction of a surface soil from the North Carolina Coastal Plain. Duplicate suspensions of silt + clay fractions from a Cape Fear sandy clay loam (fine, mixed, semiactive, thermic Typic Umbraquult) were reduced in a continuously stirred redox reactor for 40 d. We studied the effects of three treatments on P dissolution: (i) 2 g dextrose kg −1 solids added as a microbial carbon source at time 0 d; (ii) 2 g dextrose kg −1 solids split into three additions at 0, 12, and 26 d; and (iii) no added dextrose. After 40 d of reduction, concentrations of dissolved reactive phosphorus (DRP) were similar for all treatments and increased up to sevenfold from 1.5 to 10 mg L −1 The initial rate of reduction and dissolution of DRP was significantly greater for the 0‐d treatment. A linear relationship ( R 2 = 0.79) was found between DRP and dissolved organic carbon (DOC). Dissolved Fe and Al and pH increased, suggesting the formation of aqueous Fe– and Al–organic matter complexes. Separate batch experiments were performed to study the effects of increasing pH and citrate additions on PO 4 dissolution under aerobic conditions. Increasing additions of citrate increased concentrations of DRP, Fe, and Al, while increasing pH had no effect. Results indicated that increased dissolved organic matter (DOM) during soil reduction contributed to the increase in DRP, perhaps by competitive adsorption or formation of aqueous ternary DOM–Fe–PO 4 or DOM–Al–PO 4 complexes.