Biochar and Organic Matter as Tools for Mitigating Microplastic Effects in Agricultural Soils

Microplastic (MP) contamination threatens soil health, yet effective remediation strategies remain underexplored. This study aimed to address this gap by evaluating the impact of biochar and organic matter on the properties of MP-contaminated soils. Sandy loam (SL) and clay loam (CL) soils were contaminated with 1% (w/w) low-density polyethylene MPs and amended with organic matter (rice husk, compost, cow manure) or their biochar at 2% and 5% (v/v) rates in a 100-day incubation experiment. Results showed that biochar reduced pH to 7.2 (vs. 7.8 in control) and EC by 55.8% in SL, while increasing it by 28.5% in CL with 5% biochar. Organic carbon rose to 17.18 g kg^-1 with organic matter and 14.43 g kg^-1 with biochar (vs. 2.53 g kg^-1 in control), phosphorus increased by up to 270.5%, and potassium by 89.1%. Bulk density decreased to 1.15 g cm⁻³, mean weight diameter improved to 0.77 mm, and microbial respiration reached 0.127 mg CO₂ g^-1 day^-1 with 5% biochar. Both amendments mitigated MP effects, with biochar excelling at higher rates. These findings suggest that integrating biochar and organic matter into soil management practices offers a promising approach by improving soil chemical, physical, and biological properties.