Growth of forages on acid soil amended with flue gas desulfurization by-products

To assess beneficial or detrimental plant growth effects when flue gas desulfurization by-products (FGD-BPs) are applied to acid soil, experiments were conducted in a greenhouse to determine growth of forages (orchardgrass, tall fescue, switchgrass, eastern gamagrass, white clover and alfalfa) on an acid pH 4.6 soil with different levels of three FGD-BPs and chemical-grade calcium carbonate (limestone), calcium sulfate and calcium sulfite. The FGD-BPs tested were high-CaSO4, high-CaSO4 enriched with Mg, and high-CaSO3. Maximum total plant dry matter (DM) was obtained when similar to 25% of high-CaSO4 FGD-BP or similar to 2.5% of high-CaSO4 FGD-BP + Mg was incorporated into soil mixes; DM decreased at higher levels of addition. High-CaSO3 FGD-BP benefited growth of all species when added at levels up to similar to 3.0% in soil mixes. Beneficial plant responses were higher for the high-CaSO4 FGD-BPs than for the high-CaSO3 FGD-BP. Maximum beneficial plant responses for limestone were at similar to 0.25-0.50% and for CaSO4 at 50-75% in soil mixes, which were comparable with the high-CaSO4 FGD-BP and high-CaSO4 FGD-BP + Mg responses. Chemical-grade CaSO3 gave no beneficial growth effects on any of the plant species. The FGD-BPs used in this study benefited forage growth when added at appropriate levels.