Tuesday, November 14, 2006

Phosphorus Stabilization: Effects of Co-Blending Mg and Al By-Products in Manure-Impacted Spodosol.

Michael K. Miyittah1, Jack Rechcigl1, Craig Stanley1, and Martin Adjei2. (1) UFL-Gulf Coast Research Center, 14625 County Rd 672, Wimauma, FL 33598, (2) University of Florida, 3401 Experiment Station, Ona, FL 33865-9706, United States of America

Soil properties and P dynamics can be affected by long-term manure depositions, which may create environmental risks associated with P losses.  Sequential P extraction from manure-impacted soil revealed that dominant phosphorus forms associated with Ca-Mg, Al-Fe, labile P and organic P were 60-70%, 20-30%, 10-20%, and a small percentage as organic P respectively. The objective of this study was to bind all P forms by co-blending Mg by-products with aluminum-based water treatment residual (Al-WTR). The study focused on, using magnesium-based amendments since dairy manure-impacted soils tended to be calcium saturated. Leaching study, using (Al-WTR) amendment to control P encountered pH excursions in both unamended and amended soils. The pH excursions were mainly due to continuous release of loosely bound Ca-Mg associated P into soil solution. Dissolved phosphorus was positively correlated to Ca and Mg. Preliminary results from a short-term incubation study showed that, low activity magnesium oxide, and slag tend to tie strongly the P associated with Ca-Mg, although both materials did equally and greatly sorb labile P. Magnesium materials also sorbed labile P greater (P < 0.001) than Al-WTR. The Al-WTR on the other hand, showed greater (P < 0.001) influenced on phosphorus associated with Fe-Al during the sequential extraction procedure. Results suggest that by co-blending these amendments, all P forms in manure-impacted soils can be bound tightly to reduce off site P releases.