Field Studies On the Use of Flue Gas Desulfurization (FGD) Gypsum In Agriculture.

Flue gas desulfurization gypsum (FGDG) is a product of precipitation of sulfur from stack gases from coal-fired electric power plants.  This material is produced in increasingly large quantities by electric power companies to meet clean air standards.  We have evaluated this material for beneficial uses in agriculture in Indiana and Wisconsin from 2009-2011 on corn, soybean and alfalfa.  Soil, shallow ground water (-60 cm) and plant/grain samples were evaluated for increases in elemental contents due to application of FGDG at agronomical rates.   We applied FGDG or natural mined gypsum (MG) at a rate of 2.24 MT ha^-1 FGDG in replicated and randomized field plots and measured 28 different elements by ICP-MS or other techniques to ppb or ppt levels in soil, -60cm shallow groundwater, plant tissues and grain.  We found no statistically significant increases in any of these elements compared to a control or MG.   Ear leaves of corn contained greater Hg contents than mature fodder which was significantly greater than in grain.  Increasing the rate of FGDG to 8.98 MT ha^-1 applied to alfalfa did not produce significant differences in any elements and most notably did not increase Hg in the plant tissue although the FGDG contained an abnormally high amount (1.3 ppm) of Hg.  We have concluded that using FGDG at agronomical reasonable rates as a soil amendment does not have an increased risk of producing toxic element contamination in soil, plant, or grain as compared to a control or MG.  The impact of this research is that farmers can safely apply FGDG as a soil amendment at agronomical rates to crops and forages without having a significant risk of introducing toxic elements into the food chain.