THE USE OF EARTHWORMS IN ENVIRONMENTAL-MANAGEMENT

During the past 25 yr, research by the authors at Rothamsted Experimental Station investigated many aspects of the utilization of earthworms in land improvement and environmental management. Results of some of these investigations are summarized in this paper with the aim of illustrating the general principles of how earthworm populations can be manipulated and managed for environmental improvement. The use of earthworms in land improvement and reclamation: we investigated the effects of inoculating earthworms of the species Lumbricus terrestris L., Aporrectodea longa (Ude), Aporrectodea caliginosa (Sav.) and Allolobophora chlorotica (Sav.) into intact soil profiles in the laboratory, plots on direct-drilled, amble land in the field and newly-capped waste disposal sites that had few or no earthworms. In all these studies the earthworms increased significantly m number and rate of growth and yield of plants growing on the inoculated sites. Earthworms for inoculation were obtained by field collection after watering soil with dilute formaldehyde solution. The use of earthworms in organic waste management: the life cycles and productivity of Eisenia fetida (Sav.), Eudrilus eugeniae (Kinberg), Perionyx excavatus (Michaelsen) and Dendrobaena veneta (Rosa), and their potential in processing animal and plant wastes, from sewage, agricultural, domestic, urban and industrial sources are summarized. The preprocessing of wastes, their population ecology, optimum stocking rates, the mechanization of processing and utilization of the product are discussed. Results of experiments on the effects of temperatures of 10, 15, 20 and 25-degrees-C and a range of soil moisture contents of 70, 75, 80, 85 and 90% on the growth, cocoon production and cocoon hatching of the four species are summarized. The use of earthworms in assessment of the environmental effects of chemicals: earthworms can be used as key indicators to predict the effects of chemicals on other soil invertebrates. Methods of testing chemicals against earthworms in field and laboratory are reviewed. Two standardized laboratory test methods, one exposing earthworms to chemicals on filter paper and one to chemicals in artificial soils are described, and the median lethal concentration (LC50) for chloracetamide, pentachlorophenol, chlordane, carbaryl, potassium bromide, copper sulfate and trichloracetic acid calculated, based on assays done in 34 laboratories. The relevancy of the two tests in environmental toxicity testing is reviewed.