Phosphorus Sorption Behavior in a FGD Gypsum-Amended Coastal Plain Soil.

Flue Gas Desulfurization (FGD) gypsum, by-product of a process used by coal-fired power plants to prevent SO₂ release into the atmosphere, is increasingly used as an agricultural soil amendment due to improved technology producing a cleaner product. This study is measuring the impact of surface-applied FGD gypsum (0, 5, 10, or 15 Mg ha^-1) on P sorption behavior in a heavily manured Coastal Plain soil subject to potential P-loss via subsurface flow. Water extractable phosphorus (WEP) decreased by 13-47% after application of shallow-incorporated FGD gypsum in the 2012 to 2013 field experiment. We are currently running exploratory analysis on these same soil samples with ammonium oxalate and Mehlich 3 extractions of P, Al, and Fe in order to understand some of the chemical relationships following gypsum addition and how they compare to what is currently available in the literature. Additionally, we have run sorption isotherms on the samples in order to identify potential FGD gypsum effects on P sorption behavior in the soil.