Influence of flue gas desulfurization gypsum on reducing soluble phosphorus in successive runoff events from a coastal plain bermudagrass pasture

Authors: Watts, Dexter; Torbert, Henry - Allen

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2015
Publication Date: 4/25/2016
Publication URL: http://handle.nal.usda.gov/10113/62732
Citation: Watts, D.B., Torbert III, H.A. 2016. Influence of flue gas desulfurization gypsum on reducing soluble phosphorus in successive runoff events from a coastal plain bermudagrass pasture. Journal of Environmental Quality. 45:1071-1079.

Interpretive Summary: Phosphorus (P) loss from pastures heavily fertilized with poultry litter (PL) may cause algae blooms in nearby rivers, lakes, and streams. Applying gypsum to agricultural fields fertilized with PL litter has been suggested as a practice to reduce movement of P from these pastures. Thus ion this study, flue gas desulfurization gypsum from power plant generation (FGD gypsum) was added to bermudagrass pastures fertilized with PL to reduce P losses. Three separate rainfall simulation were conducted to evaluate the potential for gypsum to reduce P losses. The simulation times evaluated were immediately, 5 wk, and 6 months after Pl and gypsum application. The greatest P loss from the pasture receiving PL occurred during rainfall simulations immediately after application. Addition of FGD gypsum effectively reduced the cumulative P loss by 51%. Reduction in P loss was also observed in runoff from succeeding rainfall simulations occurring 5 wk and 6 months after application. The results shows that FGD gypsum can be used as a management tool to reduce P loss from bermudagrass pasture fertilized with PL regardless of whether the runoff occurs immediately after application or 6 months later.

Technical Abstract: Controlling the potential threat that pasture systems which have been intensively fertilized with poultry litter (PL) pose to accelerate eutrophication of surface waters has become a major issue in the southeastern U.S. Gypsum has been identified as a promising management tool for ameliorating the environmental influences litter-P losses imposes on surface water quality. Thus, research was conducted to elucidate the residual effects gypsum has on reducing P losses in an established bermudagrass (Cynodon dactylon L.) pasture. Rainfall simulations were conducted to create 60-min runoff events on a Coastal Plain soil (Luverne sandy loam; fine, mixed, semiactive, thermic Typic Hapludults). Treatments consisted of applying 4 flue gas desulfurization (FGD) gypsum rates (0, 2.2, 4.4, and 8.9 Mg ha-1) to bermudagrass fertilized with 13.4 Mg ha-1 PL plus a non-fertilized check (no litter or FGD gypsum) and 8.9 Mg ha-1 FGD gypsum alone as controls. All treatments were applied each May from 2009 to 2011. A total of 3 rainfall simulations were conducted, immediately, 5 wk, and 6 months (end of growing season), following PL application to determine FGD gypsum’s effectiveness at controlling P loss over time. The greatest soluble P (SP) concentrations in runoff occurred immediately after PL application. Addition of FGD gypsum effectively reduced SP losses in runoff up to 51%. Soluble P concentrations were also reduced in succeeding runoff events with FGD gypsum regardless of timing, suggesting that its effect is persistent and will not diminish over a growing season. Generally, maximum SP reductions were achieved with 8.9 Mg ha-1. However, it was surmised from this study that the most feasible application rate for optimal P reduction in a bermudagrass pasture was 4.4 Mg ha-1. The information ascertained from this study may be useful in aiding land managers making prescriptions for best management practices that reduce SP losses from agricultural fields.