Effects of fly ash on microbial CO sub(2) evolution from an agricultural soil

Unweathered, acidic fly ash from a coal-fired power plant was applied to alfalfa meal-amended agricultural soil at levels equivalent to 0. 100, 400, and 700 ton ha super(-1). Amended soils were placed in respirometer jars and monitored for CO sub(2)-C evolution over a 37 day period. Fly ash applications of 400 and 700 ton ha super(-1) reduced CO sub(2)-C production significantly compared to 0 and 100 ton ha super(-1) treatments. Carbon dioxide-carbon from all treatments was considerably greater than that from soil treated with 1000 ppm CDCl sub(2). The results suggest that soil heteortrophic microbial activity may be impacted minimally by relatively low levels of fly ash application, but may be inhibited by higher levels of fly ash. Several metals were present at potentially toxic levels in the fly ash employed and may have accounted for the inhibition of CO sub(2)-C evolution. The availability of some of these metals was indicated in comparison plant uptake experiments.