Fertilizers are intentionally added to the soil to improve the crop yield. But their application may affect the soil organisms, particularly earthworms and thus the soil fertility may end in risk. Soil fertility is the ability of soil to function within natural and managed ecosystems and depends on physical, chemical and biological properties of the soil. Most of these qualities cannot be measured directly, but are typically inferred from soil properties that serve as indicators. Earthworm is one such indicator which is used for monitoring the soil fertility. Potash is a worldwide used mineral fertilizer that is applied to crops for supplying potassium. An acute toxicity test of potash to earthworms (Eisenia foetida) was performed using a simple paper contact method proposed by OECD (Organization for Economical and Cooperative Development) testing guideline no. 207. The worm was exposed to the deposit of potash kept uniform on filter paper for 48 h and the mortality was recorded. The concentrations were expressed in μg/cm2. Based on the resulting LC50 value, the potash was classified as “very toxic” to earthworm. The result of this study further demonstrates that the inorganic chemical 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 potash.
