A Study of the Effects of Applying Flue Gas Desulphurization Gypsum to Various Agronomic Crops

Flue Gas Desulfurization (FGD) gypsum is a potential soil amendment for agricultural use in the state of Tennessee. FGD gypsum is a potential source of calcium and sulfur that may improve the soil both chemically and physically. FGD gypsum has the potential to raise pH, improve soil structure, increase infiltration rates, ameliorate subsoil acidity and improve crop yields. However, the addition of gypsum can also lower pH in some circumstances and cause magnesium and potassium losses in soil. In this study FGD gypsum was applied at a single rate to fields on thirteen farms located on the northern and southern Highland Rim and in the southern Outer Central Basin region of the state.

These fields were then managed in conjunction with the farms’ conventional practices. Soil samples were collected and analyzed for pH, K, Ca, Mg and Al. Results showed that the application of FGD gypsum can either increase or decrease pH with the dependent factor seeming to be the initial pH level of the soil. Decreases were seen in K and Mg content of the soil. On the sites with the most acid subsoils, exchangeable aluminum was reduced in the upper subsoil. Increases in Ca were observed deep into the profile after the second year of the study. Soil physical properties were largely unchanged, as indicated by penetrometer, soil water and bulk density measurements.

It is believed that the traffic associated with the application of the FGD gypsum negated most of the beneficial structural effects that are often seen with mined gypsum. Also since most of the locations were managed as no-till systems the effects of gypsum on water infiltration were negated by the residue left on top of the soil surface. This resulted in the absence of effect in the soil water measurements that were collected over the two years of the study. Corn yields were seen to improve after the application of FGD gypsum indicating the material is potentially a viable option for some farming operations in the state.