| Abstrakt: |
A field study of five coal surface mine sites reclaimed with sewage sludge and one site reclaimed by conventional methods (chemical fertilizer) was conducted to assess the effects of sludge amendments and time on populations of bacteria, fungi, and actinomycetes, and on microbial respiration and organic matter decomposition. The sludge‐amended sites ranged in age from 1 to 5 yr following sludge application at rates of 120 to 134 Mg ha−1(dry wt. basis). All sites were planted to grass and legume cover. Populations of aerobic heterotrophic bacteria, fungi, and Nitrobacter,and soil respiration rate, were highest on the 1‐yr‐old site due to the high organic matter input. On the four older sites, values decreased, but remained within the ranges reported for undisturbed soils. Actinomycete populations peaked on the 3‐ and 4‐yr‐old sites, while populations of Nitrosomonaswere not related to the age of the site. Decomposition rate was lowest on the 1‐yr‐old site, and increased significantly with site age. As measured by microbial populations and activity, ecosystem recovery on the sludge‐amended sites appeared to be occurring at a more rapid rate than on the fertilizer‐amended site, which after 5 yr, exhibited sparse microbial populations and low activity. The microbial populations in the sludge‐amended spoil were not adversely affected by the heavy metals applied in the sludge, when compared with populations of soil microbes reported for undisturbed soils. |
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