Effects of fly ash on soil microbial activity

Fly ash was added to a sandy soil and a sandy loam to study its effects on soil microbial respiration. Microbial respiration was reduced with increasing fly ash treatments in the sandy soil, whereas in the sandy loam, a significant depression was only recorded at the highest ash addition for both total and cumulative carbon dioxide evolved. Total carbon dioxide release was actually increased by 3% and 6% ash amendment on the sandy loam. A highly negative correlation was found between respiration and ash treatment for the sandy soil (r = −0·9904, p < 0·005), but not for the sandy loam. Ecological dose 50% (EcD₅₀) values of the sandy soil were smaller than that of the sandy loam for each period. The reasons for this are discussed.