The effects of different inputs of organic growth medium and anaerobic digestate on earthworms at the former Chisnall Hall colliery waste tip

Abstract

Chisnall hall colliery is historically the site of extensive coal mining operations which shut down during the 1900’s leaving large amounts of colliery spoil on waste heaps. The Chisnall hall colliery spoil heap was repurposed for grazing and received numerous restoration attempts with the current aim to create new woodland for community use.
Global renewables is a company working with Lancashire County Council towards possible applications of Anaerobic Digestate and Organic Growth Medium to improve soil quality and structure on reclamation sites and is studying the potential for the two substances to act as fertilisers for bio-crops on reclamation projects through testing at the Chisnall hall location. The intention of this study is to determine how the different applications of Anaerobic Digestate and Organic Growth Medium affect the earthworm communities to complement the existing study.
Research methods involved collection of primary data from the field and subsequent laboratory analysis of both soil properties and earthworms. The literature surrounding the project was also drawn upon with particular reference to anaerobic digestate, earthworm ecology the interactions with soil systems and their impact on land reclamation.
10 different species were identified throughout the study along with two versions of Allolobophora chlorotica with endogeics being the most abundant group. Willow crops proved to be the most beneficial for earthworm communities and all the application types whether pure or mixed seemed to increase both biomass and population levels. Pure AD applications had the greatest potential but had the added effect of being highly variable with its success, with earthworm communities either flourishing or faring poorly at increasing extremities with greater application rates.
Soil pH floated consistently around neutral or slightly alkali conditions, with wet soil moisture conditions throughout and ample amounts of organic matter present within the soil as would be expected with additions of fertiliser and soil structure remediation.
Control groups showed consistently lower levels of success for all factors and both soil properties and structure were of poorer quality for supporting soil fauna.