Assessment of acute toxicity of superphosphate to Eisenia foetida using paper contact method

Superphosphate was the most widely used phosphate fertilizer in agricultural fields. It is applied to the soil to increase and to maintain soil phosphorus levels. The ultimate goal is of maximizing productivity and economic returns, while side effects on soil organisms are often neglected. Another important indirect effect especially of superphosphate (SP) fertilization is soil acidification, with considerable negative effects on earthworms. Earthworms are typically inferred as soil indicators without which soil fertility cannot be measured directly. An acute toxicity test of SP to earthworms (Eisenia foetida) was performed using paper contact method proposed by OECD (Organization for Economical and Cooperative Development) testing guideline no. 207. The worm was exposed to the deposit of SP kept uniform on filter paper for 48 h and the mortality was recorded. The lethal concentration was recorded as 210mg/5ml (i.e. 300μg/cm2). Based on the resulting LC50 value, the SP was classified as “moderately toxic” to earthworm, Eisenia foetida. The result of this study further demonstrates that the inorganic mineral fertilizer can also be toxic to earthworms when contacted directly. Thus there arises an unavoidable need of monitoring the usage of fertilizer dosage on agricultural lands, particularly the superphosphate.

Author(s): Kovilpathu Senthil Kumar Abbiramy*, Pankiras Ronald Ross and Jyothi Pillai Paramanandham

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