TOXICIDADE SUBCRÔNICA DA ASSOCIAÇÃO ENTRE IODO DE CURTUME, ESTERCO BOVINO E IATOSSOLO VERMELHO SOB Eisenia fetida

Abstract

Concern about the polluting potential of waste produced by Tanneries has fostered two lines of research that seek environmentally correct disposal associated with soil fertilization. The first performs the deposition of waste in natura directly on the soil, and the second stabilizes the waste by means of vermicomposting, before incorporating it into the soil. Both present interesting results individually, however no study has yet analyzed the effect of fresh sludge on the soil on earthworms, which can carry out vermicomposting on the soil itself. Thus, the objective of this study is to evaluate the subchronic toxicity of different doses of tannery sludge deposited in the soil under earthworms of the species Eisenia fetida. Different concentrations of tannery sludge (0%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%) associated with 20% of tanned cattle manure and Red Latosol were evaluated. The treatments contained seven replicates each in a completely randomized design (N= 63), with 20 earthworms in each unit and humidity maintained between 40% and 60%. Treatments between 10% and 60% were lethal to all worms in the first 24 h. Group 5% was equivalent to Lethal Concentration 50 (LC50), in which 50% of individuals died. Regarding the number of earthworms at the end of the study, joint mass and individual mass of the earthworms, the 5% group showed statistically lower values than the Control group and 1%, which in turn were statistically equal, showing mass gain compared to the beginning of the study. It was concluded that high concentrations of sludge in natura, with these characteristics, deposited in the soil can be lethal to earthworms, harming the important role they play in the soil, but the deposition of concentrations of 1% (20 t ha-1) is promising as sludge disposal and soil fertilization without causing the death of the studied worms.