Effects of biochar on the earthworm (Eisenia foetida) in soil contaminated with and/or without pesticide mesotrione

Abstract

The plant-derived biochars act as soil conditioners, and thus may influence biological interactions in the soil environment. However, their unintended negative and positive effects on soil organisms remain largely understudied. Therefore, we investigated the effect of 0, 1, 3, and 10% of wheat straw-derived biochar amendments on earthworm (Eisenia foetida) activity in the soil contaminated with and/or without pesticide mesotrione (10 mg/kg dry soil) after 28 days of incubation. The pesticide mesotrione did not affect earthworm growth or reproduction; however, it induced oxidative stress and DNA damage. Although biochar application significantly decreased the concentration of mesotrione in earthworms, it delayed the degradation of pesticide in the soil environment. Compared to zero amendment, the amendment of 1 and 3% of biochar significantly increased (P < 0.05) the earthworm weight and reduced the toxicity effects of mesotrione on earthworms. However, the application of 10% biochar significantly decreased (P < 0.05) earthworm growth and caused DNA damage even in the absence of mesotrione. This study suggests that it is necessary to investigate the effects of different levels of biochar amendments on earthworms and other soil organisms in agricultural fields to develop a broader understanding about the use of biochar and its consequences on soil health.