Impact of Flue Gas Desulfurization Gypsum Applications to Corn-Soybean Plots on Surface Runoff Water Quality

Row crop agriculture systems are a significant contributor to non-point source nutrient loading into water bodies. One approach to reduce phosphorus (P) losses through surface runoff is applying flue gas desulfurization (FGD) gypsum as a soil amendment. This research was conducted to examine the effects of different rates of FGD gypsum application to corn (Zea mays L.)-soybean (Glycine max) plots on water quality parameters including dissolved reactive phosphate (DRP), total phosphorus (TP), and total suspended solids (TSS). The study was conducted on a high P level (>30 mg P kg(-1)) soil in a completely randomized design with four treatments each replicated three times. The four treatments were no FGD gypsum (control), FGD gypsum at a rate of 2.2 Mg ha(-1), FGD gypsum at 4.5 Mg ha(-1), and FGD gypsum at 13.5 Mg ha(-1). Gypsum applications were effective in reducing P loads in surface runoff water, with a significant (P < 0.1) reduction in DRP and TP from all the treatments compared to the control during the initial post-gypsum application period (December 2018-May 2019). Results suggest application rates of 4.5 Mg ha(-1) and 13.5 Mg ha(-1) were most suitable to reduce P loads in surface runoff water from Hosmer silt loam soil with high soil test P (STP) prior to P fertilizer application. However, following P fertilizer application (May 2019-January 2020), gypsum was not effective in reducing P in surface runoff. Overall, FGD gypsum appeared to be an effective phosphorus abatement tool for southern Illinois soils to improve water quality. Though, how long it remains effective appears to be in question given our results in the post P fertilization period.