Effects of Energy Crop Monocultures and Sewage Sludge Fertiliser on Soils and Earthworm Community Attributes

Biomass is one of the most significant renewable energy sources. Doubts arise from large-area plantations of energy monocultures, which can lead to the depletion of, and a decrease in, soil biodiversity. Community association analyses of Lumbricidae may help to indicate environmental change. Therefore, the study objectives were to determine the qualitative and quantitative diversity of Lumbricids in plantations of energy crops—basket willow (Salix viminalis L.), foxglove tree (Paulownia tomentosa Steud.), and black locust (Robinia pseudoacacia L.)—by investigating the following cultivation treatments: SV and SVSS—S. viminalis without (w/o) and with the addition of sewage sludge to the soil (+SS); PT and PTSS—P. tomentosaw/o and + SS; RP and RPSS—R. pseudoacaciaw/o and +SS; and MW—meadow community. A significantly higher density (p < 0.05) and biomass (p < 0.05) of earthworms were found in the SV and SVSS plantations than in other sites. The application of sewage sludge contributed to a significant increase in the mean number and biomass of all Lumbricids within cultivations of S. viminalis and R. pseudoacacia, which were significantly higher than those in the control site. This work suggests that woody energy crop production with an appropriate selection of plants and fertilisation can be a favourable habitat for the development of earthworm populations.