Groundwater-induced accumulation of iron oxides and phosphorus retention in severely leached soils
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Many sandy soils of the Swan Coastal Plain, Western Australia, are poor in Fe and P retention. A novel concept proposes to relocate Fe from groundwater to surface soils via watering, which should consequently improve P retention. To test the viability of this concept we examined several soils in Perth suburbs that had been watered for 3-27 years with groundwater containing high Fe. Energy dispersive X-ray microanalysis indicated that 'Fe-watered' soils had significantly higher Fe materials on the surface of soil particles. Oxalate-extractable Fe (Feo) increased by 52 times and citrate/dithionite-extractable Fe (Fed) increased by 6.6 times. Unusually high Feo/d ratios (average Feo/d=0.71) in 'Fe-watered' soils strongly suggest that the accumulated Fe materials are predominantly amorphous and secondary Fe oxides, probably ferrihydrite. There was a substantial increase in P retention in top-soils, to a magnitude of 45-128 times, demonstrating that increasing Fe oxides in severely leached soils, caused by groundwater irrigation, increases P retention. This approach could be applied to other areas with similar physical characteristics and the present study demonstrates that watering with Fe rich groundwater might have strategic significance not only in the control of water pollution, but also in the rational use of water resources and the amelioration of soil salinisation associated with rising watertables.
|Publication Type:||Journal Article|
|Murdoch Affiliation:||School of Environmental Science|
|Copyright:||© 2004 CSIRO|
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