Effects of biochar on fate and toxicity of herbicide fenoxaprop-ethyl in soil

The biochar as soil amendment in agriculture has attracted considerable attention. In the study, the fate and toxicity of the herbicide fenoxaprop-ethyl were evaluated in soils with and without 5% rice husk biochar amendment. Fenoxaprop-ethyl and metabolite fenoxaprop degraded followed first-order kinetics in the two soils. Fenoxaprop-ethyl decreased fast with half-lives less than 2 days. Large amounts of fenoxaprop formed and remained in control soil. However, fenoxaprop was much lower in biochar-amended soil with reduction over 85% at the 35th day. The estimated half-lives of fenoxaprop were 56.9 and 1.5 days in control and biochar-amended soils, respectively. Biochar restrained the formation and promoted the dissipation of fenoxaprop. Biological indicator earthworms (Eisenia fetida) were used in a 14-day acute toxicity test. Fenoxaprop-ethyl shown low toxic to earthworms with LC50 value of 322.9 μg/g. Biochar amendment was nontoxic to earthworms and effectively reduced the toxicity. ...