Evaluating phosphorus release from biosolids and manure-amended soils under anoxic conditions.
The solubility of P in biosolids and manures has been shown to influence the potential for dissolved P losses in runoff and leachate when these materials are land applied. As a result, some Mid-Atlantic US states have developed P source coefficients (PSCs) to account for differences in P solubility between fertilizers, manures, and biosolids in P risk assessment tools. The reliability of these PSCs has not been evaluated under anoxic conditions, where environmental changes may affect the P solubility of biosolids or manures. The objective of this study was to assess the effects of anoxic conditions on the release of P from a range of Mid-Atlantic soils amended with manures and biosolids. The concentration of dissolved P released into solution (0.01 mol L(-1) NaCl) from the Pamunkey, Berks, and Manor soils was significantly lower under reducing conditions than under oxidized conditions (median DeltaP = -0.70, -0.49, and -0.07 mg L(-1), respectively; all significant at the 0.001 probability level). There was no significant P source effect on dissolved P released into solution after anoxic incubation of soils. Calculated solubility diagrams and increases in oxalate-extractable Fe and P sorption index under reducing conditions for all soils suggest the precipitation of (i) an Fe(II)-oxide that increased the P sorption capacity of the soils or (ii) an Fe(II)-phosphate that decreased the solubility of P. We propose that current PSCs do not need alteration to account for differences in P solubility of organic sources under reducing conditions under relatively static conditions (e.g., seasonable high water table, periodically submerged soils, stagnant drainage ditches).
Shober
Amy L
AL
Soil and Water Science Dep., University of Florida Gulf Coast REC, Wimauma, FL 33598, USA. alshober@ufl.edu
Sims
J Thomas
JT
D006863:Hydrogen-Ion Concentration; D000860:Hypoxia; D008372:Manure; D008873:Mid-Atlantic Region; D009943:Organophosphorus Compounds / Q000032:analysis; D010084:Oxidation-Reduction; D010758:Phosphorus / Q000032:analysis*; D012722:Sewage; D012987:Soil / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
D008372:Manure; D009943:Organophosphorus Compounds; D012722:Sewage; D012987:Soil; D014874:Water Pollutants, Chemical; D010758:Phosphorus