One of the latest and cost-effective methods of reducing soil pollution caused by pesticides is the use of biochar. The aim of this study was to determine the effects of different levels of wheat straw biochar (0, 1.5, and 3 wt%) added to sandy loam soils on deltamethrin sorption, degradation, and leaching potential for a two-year experiment (2018 and 2019). The results showed the lower leachability of deltamethrin in the 1.5 and 3% of biochar compared to 0% of biochar-amended soil. The average sorption of deltamethrin in non-amended soil was almost 10% higher than in biochar-amended soil. The deltamethrin degradation was slightly faster in 0% than 1.5 and 3% biochar-amended soil, so that the half-life of deltamethrin decreased from 38.5 to 36.4 days. The highest and lowest mean of soil moisture content were related to 3 and 0% of biochar-amended soil, with a significant increase of more than 200% for 3% compared to 0% of biochar. As compared to 0wt% of biochar, the mean electrical conductivity (EC) of soil significantly increased by adding 3% of biochar to the soil from 0.12 to 2.1 dS m−1
