ARS | Publication request: UPPER PROFILE CHANGES OVER TIME IN AN APPALACHIAN HAYFIELD SOIL AMENDED WITH COAL COMBUSTION BY-PRODUCTS

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2005
Publication Date: March 20, 2006
Citation: Zhou, X., Ritchey, K.D., Clark, R.B., Persaud, N., Belesky, D.P. 2006. Upper Profile Changes Over Time in an Appalachian Hayfield Soil Amended with Coal Combustion By-products. Communications in Soil Science and Plant Analysis. 37:1246-1267.

Interpretive Summary: In grasslands, problems of soil acidity are usually addressed by surface application of limestone and pH amendments, rather than by incorporation of the materials. This implies that, to a certain extent, liming agents need to be soluble in order for their benefits to be available to plants. Current recommended rates of application may have been developed based on experiments where liming materials were mixed into the plow layer. We used an acid extraction method to determine the amounts of two surface-applied amendments (agricultural limestone and fluidized bed combustion residue, a coal-fired power plant by-product) that were still present on or in the top inch of the soil surface 6 years after it was broadcast onto a hayfield. We found that a considerable portion of the calcium applied in these amendments still had not dissolved after 6 years. This information is important to farmers who need to know that much of the limestone they surface-apply to grasslands is not active in overcoming soil acidity. It may be appropriate to either apply more amendment or periodically plow grasslands to order to incorporate inputs and increase their availability.

Technical Abstract: Large amounts of flue gas desulfurization (FGD) and fluidized bed combustion (FBC) by-products from burning coal, consisting primarily of gypsum, are available for potential use as a soil amendment. However, information is limited on longer-term changes in chemical and physical properties induced over time and over small depth increments of the upper soil profile after applying these amendments. This study examined longer-term effects in an abandoned Appalachian pasture soil amended with various liming materials and coal combustion by-products (CCBPs). Soil chemical and physical properties were investigated over time and depths. The results indicated limited dissolution and movement of the Ca and Mg applied with the chemical amendments, except for Ca and Mg associated with sulfate. However, sufficient dissolution occurred to cause significant increases in exchangeable Ca and Mg and decreases in exchangeable Al that were reflected in corresponding increases in soil pH. These beneficial effects persisted over time, and were confined to the upper 0- to 15- cm depth of the profile. The greatest benefits appeared to be in the upper 0- to 5- cm surface layer. Both Ca and Mg applied as calcitic dolomitic limestone tended to be immobilized in the upper 0- to 5- cm layer of the soil profile; Ca more so than Mg. The presence of S applied in the FGD and FBC amendments appeared to enhance the mobility of Ca and Mg. The ratio of Ca/Mg in HCl extracts from the calcitic dolomitic treatment was close to that of applied calcitic dolomite, implying that the inactive component in soil might be the original calcitic dolomite particles. Soil physical properties measured over small depth increments showed that application of the amendments improved the saturated hydraulic conductivity only in the upper 0- to 5- cm depth, and had little or no significant effect on the dry bulk density and plant available water.