Potential of Flue-Gas Desulfurization (FGD) Gypsum for Reducing Phosphorus Runoff Losses.

Potential of Flue-gas Desulfurization (FGD) Gypsum for Reducing Soil Phosphorus Losses

K. Brewer, F.J. Arriaga

It is well known that water quality is greatly impacted by nutrient runoff from agricultural fields. Phosphorus is of particular interest due to its status as a limiting nutrient in natural systems. Even very small quantities of P can have a large impact on these systems and lead to eutrophication. Previous studies have shown that flue-gas desulfurization (FGD) gypsum can reduce P losses from runoff. However, the impact of various FGD application rates to soil with varying soil test phosphorus levels is not well understood. The aim of this study is to look at these issues on a laboratory scale.

Soil was collected to a 15 cm depth from an agricultural field near the Milwaukee River Watershed for use in laboratory incubations. Initially the soil was analyzed for Bray P1, K, pH, and water extractable P. Water extractable P has been shown to be a representative measure of dissolved P that can be readily transported during a runoff event. The soil was incubated at 75% field capacity water content with three phosphorus spiking treatments (0, +100 ppm, and +200 ppm) for 26 days.  After the initial 26 day equilibration period, a subsample was removed for P analysis (water extractable and Bray P1), and the assigned FGD gypsum treatment will be applied (0, 0.5, 1, 2 and 4 tons/ac). The second incubation of 21 days will be followed by Bray P1, water extractable P, K, and pH analyses. Long-term these data will be compared to field level runoff data to assess possible relationships. Thus, the overall goal of this laboratory incubation is to determine the impact of different FGD gypsum application rates on water extractable and Bray-1 soil P fractions.