Indicators of microbial activity in the assessment of soil condition subjected to several years of reclamation

Abstract

The investigations were carried out in the form of a field reclamation experiment established in the former “Jeziórko” Sulphur Mine (Poland). For soil reclamation, various combinations of sewage sludge, mineral wool, post-flotation lime and mineral fertilisation were introduced in a single application to the degraded soil. The following parameters were determined in the reclaimed soil in spring and autumn of the 2nd and 3rd year after waste application: number of oligotrophic, cellulolytic and lipolytic bacteria, number of filamentous, cellulolytic and lipolytic fungi, respiratory activity, intensification of cellulose mineralisation, lipase activity and DNA concentration. The applied wastes had a stimulating effect on the growth of the analysed bacterial groups. The growth of fungi was stimulated only in the soil treated with sewage sludge, whereas the values of these parameters in other treatments were usually reduced. The addition of wastes contributed to the intensification of respiration processes and cellulose mineralisation. Lipase activity and DNA concentration fluctuated depending on the type of waste and the time period of investigations; these parameters exhibited the highest values in the soil treated with sewage sludge. In general, the increase in microbiological and biochemical activities was clearly evident in the soil treated with sewage sludge applied separately or in combination with other wastes. The use of sewage sludge together with post-floatation lime, rather than sewage sludge alone, and the application of mineral wool as a 5-cm pad, rather than a mixture of mineral wool and soil, proved to be more beneficial for most of the analysed parameters.The current study is important in the context of safe and effective application of waste for reclamation purposes. In addition, the work raises the innovative aspect of using DNA concentration as an indicator of degraded soil status.