Evaluation of Environmental Benefits of Application of FGD-Gypsum to Agricultural Fields: Runoff, P and K.

Large amounts of flue gas desulfurization (FGD) gypsum are expected to be produced annually in the coming decades from use of FGD systems to reduce sulfur dioxide emissions from power plants. Amending soils with FGD gypsum improves soil aggregation, infiltration, sub-soil acidity by replacing exchangeable Al, and fertility through addition of soluble Ca and S. In addition, soluble Ca will complex with soluble reactive P and reduces its concentration in runoff and its adverse effect on off-site water quality. Continuous application of broiler litter (BL) to pastures and cropland typically leads to high soil test P.  The overall objective of this study was to examine the interaction FGD gypsum and BL application on Bermudagrass pasture production and water quality issues. In two controlled rainfall simulation studies (June 2009 & June 2011) runoff and P and K losses in runoff were evaluated from treatments consisting of four rates of FGD gypsum at the highest level of BL (0-6, 1-6, 2-6, 4-6 ton/acre) and two control treatments 0-0 and 4-0 ton/acre (BL - FGD gypsum) in a randomized block design with three replications. Neither runoff nor the runoff-to-rain ratio was influenced by the FGD-gypsum or the BL treatments in the first simulation probably due to large plot to plot variability which may have been related to the very dry conditions prior to and during the rainfall simulation. There was, however, a trend for less runoff for the 4-6 and 4-0 treatments. Concentrations of P in the runoff were influenced by BL, FGD gypsum and the interaction between the two. There was a strong trend for decreasing concentrations of P with increasing concentrations of FGD gypsum. Levels of K were influenced by BL but not by FGD gypsum although there was a trend for reduced K with increasing FGD gypsum.