Relationships Between Microbial Parameters and Soil Properties in a Hydrophobic Spolic Technosol

Data on microbiology of water repellent (hydrophobic) soils in Bulgaria are scarce.This work aimed to find out relations between microbiological indicators, hydrophobicitylevel and other soil properties in a Spolic Technosol. Samples from 0-10 cm and 10-20 cmsoil depth of a fly ash reclaimed soil covered with tuft vegetation and located near Obruchistearea were collected. Main microbiological (basal respiration - BR, microbial biomass carboncontent -Cmic, amount of main microbial groups –CFU), chemical (organic carbon, availableN, P and K contents) and physical (hydrophobicity level, moisture, sand and clay contents)properties were determined. It was found that the Technosol was hydrophobic in most of themonitoring points. Half of the samples were severely or extremely hydrophobic (assessed bywater-drop-penetration time) and the hydrophobicity level was higher in the subsurface layer.The Spolic Techosol under tuft vegetation was characterized with low numbers ofheterotrophic bacteria, actinomycetes and oligotrophic microorganisms (1-40 x 102 CFU/g) at0-20 cm depth. As a whole, low BR rate (0.51-5.43 mg CO2/g/ 24h) and low Cmic values(2.37-18.18 mg C/100g) were established for both layers. Weak relationships of microbialparameters with organic carbon, humic acid, fulvic acid and clay contents were noticed in thissoil. Significant correlations of the amount of fungi and actinomycetes with available nutrientand moisture contents were found.In general, a trend of positive relationships of fungi, actinomycetes and cellulolyticmicroorganisms with soil hydrophobicity was established. The relative parts of fungi andactinomycetes increased in the hydrophobic samples comparing to non-hydrophobic ones.Microbial biomass carbon tended to increase with increasing the hydrophobicity level. Datapointed on close positive relationships of microbial parameters studied with thehydrophobicity in this Technosol.Our results add new information to the monitoring study of hydrophobic Technosols fromMaritsa-Iztok coal-mining region (Bulgaria).