Wednesday, November 7, 2007
327-4
Aluminum Water Treatment Residual Effects on Soil Phosphorus Retention and Forage Quality.
The movement of phosphorus (P) into freshwater bodies may lead to eutrophication and generally unhealthy biological conditions. Phosphorus loss by surface runoff has been recognized and partially managed by erosion control measures but little has been done to prevent P loss from leaching. Many soils in Florida are characterized by poor P sorbing abilities. In addition, shallow groundwater and extensive ditching result in movement of P via lateral subsurface flow. Water treatment residuals (WTR) are by-products of the drinking water purification process that contain amorphous iron (Fe) and aluminum (Al) with substantial P-fixing capabilities. Many greenhouse studies have shown the ability of WTR to sorb P in controlled environments. In addition to P retention, Al toxicity is an issue when applying Al-WTR. The purpose of this study was to analyze the effects of an Al-WTR on soil P retention and forage quality and yield under field conditions. The study site was an established bahiagrass pasture at the University of Florida Range Research and Education Center in Ona, Fl. Soils on the site are Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). A split-plot design was used for the plots (3.05m X 6.07m) with application method (surface applied versus soil incorporation) as the main plot and WTR rate (0, 35 or 70 Mg ha-1) as the subplot. WTR was applied in January 2007 and forage harvests were taken the following May and June. WTR application did not affect yield or neutral detergent fiber percentages. There was an increase in the soil P sorption capacity of the A horizon between the control and the plot with 70 Mg ha-1 of WTR.
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