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United States Department of Agriculture

Agricultural Research Service


item Stout, William
item Sharpley, Andrew
item Gburek, William
item Pionke, Harry

Submitted to: Fuel
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 19, 1998
Publication Date: N/A

Interpretive Summary: Phosphorus enrichment of streams, lakes, and fresh water portions of estuaries, such as the Chesapeake Bay, is often the cause of algae blooms in these waters. A major source of this P enrichment is runoff from croplands that have been over fertilized with animal manures and/or commercial fertilizers. One way of reducing the P in runoff is by reducing gits solubility through precipitation with other elements such as Ca, Al, and Fe. In a laboratory study, we used flyash and by-product gypsum from power plants to precipitate P in soil and reduce its potential to be exported in runoff. We also used a hydrologic model to determine the effect of the flyash and gypsum treatments at the watershed scale. From the laboratory study, we found that a relatively small application of flyash or gypsum could reduce the water solubility of soil P. The model indicated that P export from a watershed could be cut by 30% by applying the treatments to the 4% of the watershed that was contributing P runoff. This would provide a means to control P export to streams in the short term while reducing soil P levels through proper nutrient management.

Technical Abstract: Excessive soil P levels cause high concentrations of water soluble P in soil, thereby increasing the potential for P export to streams. Converting water soluble P to less soluble forms with lime or Ca containing coal combustion by-products can reduce the release of soil P to runoff. A typical agricultural soil at excessive soil P levels was incubated with four treatments (0 to 20 g kg-1) of fluidized bed combustion flyash (FBC) and a flue gas desulfurization (FGD) by-product. A 10 g kg-1 application of FBC and FGD to soil reduced the concentration of water soluble P by 60% and 50%, respectively. Projection of these results over an agricultural watershed indicates that treating only 4% of the watershed can reduce the loss of water soluble P by 30%.

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