Validation of Tropical Artificial Soil by Chronic Toxicity Studies on <i>Eisenia fetida</i> against Superphosphate

Abstract

The research methodology recommended by the OECD (Organization of Economic Co-operation and Development) and ISO (International Organization for Standardization) guidelines for testing of chemicals meets the most criteria expected for ecotoxicological testing except the testing condition and the organic matter. The guidelines were initially developed by temperate countries, with testing conditions as 20 °C and the organic matter as sphagnum peat which is commonly available in those countries. But these two criterions are difficult to be followed in tropical countries. Thus there arises a need of modifying these criterions for toxicity studied in tropical regions. In this study a trial was made for substituting the fermented coir pith for sphagnum peat and the validation of the modified tropical artificial soil (TAS) was done by conducting chronic toxicity studies on Eisenia fetida against an inorganic fertilizer, superphosphate (SP) under tropical condition, i.e., 28 ±2 °C. The performed study showed that the SP determined lower earthworm mortality in TAS comparing to OECD soil for all tested concentration levels. The number of juveniles produced in OECD soil was also significantly reduced (p < 0.05) than in TAS. This may be due to the production of large amount of hydrogen ions when the temperature increases and making the medium acidic. The fermented coir pith was more suitable for ecotoxicity studies under tropical condition than sphagnum peat.