Use of Coal Combustion by-Products (CCBP) in Horticultural and Turfgrass Industries

Abstract

Coal combustion by-products (CCBP) include fly ash, bottom ash (cinders) and various desulfurization by-products. They contain plant nutrients, have variable capacities to neutralize soil acidity, and may improve physical properties of mineral soils. They have been usefully applied in agricultural, horticultural, turfgrass and land reclamation settings. However, inherent traits of CCBP such as bulkiness, excess trace metal concentrations, inconsistent availability of P, and low content of N and K make CCBP an untenable fertilizer supplement. Likewise, utilization of municipal biosolids (sewage sludge) can be problematic due to trace metal levels and undesirable nutrient ratios. Therefore, this study was initiated in early 2000 to determine the feasibility of blended CCBP and biosolids/biosolid products for use as growth media for horticultural ornamentals and turfgrass sod. Trace element concentrations in mixes used for both soil amendment and sod media were below USEPA regulatory limits. In the sod production component, growth media were uniformly spread to heights of 2, 3, and 4 cm on compacted subsoil, sprigged with bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensisBurrtDavy var. ‘TifSport’ (formerly Tift 94)], and maintained under ideal commercial sod field conditions. Following a maturation period of 99 d, sod was harvested and installed at the Georgia Experiment Station in Griffin. Remaining sod were destructively analyzed for determination of their physicochemical attributes. Field data collected from the ornamental beds showed yield and quality of flowers grown on CCBP-amended soil to outperform the commercially-amended soil under limited fertility conditions. Post-installation evaluations of sod made in April, 2001 did not reveal significant differences in rooting strength by mixture or sod thickness. All finished CCBPcontaining sod retained significantly more volumetric water (ψm<-80 kPa), while possessing 26–39% less gross (wet) weight than the control mix sod. The finished sod grown in selected combinations of bottom ash, fly ash, and biosolids possessed significantly greater biomass than the control sod mix, while requiring less supplemental fertilization. Utilization of the described CCBP-mixes as supplemental growth media in bermudagrass sod production was successful and may be a significant advantage when compared to some SE US soils. These experimental observations, in tandem with similar published results, indicate that utilization of CCBP in horticulture and turfgrass industries is technically feasible and environmentally-sound.