Soil physical parameters and earthworm populations associated with opencast coal working and land restoration

A study of physical and biological soil parameters was undertaken on reinstated opencast coal sites of varying ages from final topsoil replacement. Earthworm population levels were determined at the same time as sampling of pH, particle size analysis and bulk density. The results indicated that the pH of a site was not limiting to earthworm activity, but that all the reinstated sites had zones of compaction which were remnants of the restoration practice and may be limiting to earthworm activity. Total earthworm populations reached levels similar to undisturbed adjacent controls within 10–20 years after topsoil replacement, although there were differences in species composition.