In a new study published in Biochar X, lead author João Ricardo Sousa and an international research team evaluated how common agricultural pollutants disrupt soil life and how biochar can lessen these impacts. Agricultural soils often receive repeated applications of copper-based fungicides and glyphosate-based herbicides. Although both chemicals are used worldwide, their combined effects on beneficial soil organisms like earthworms remain poorly understood. Earthworms maintain soil structure, nutrient cycling, and organic matter breakdown. When soil conditions become harmful, earthworms actively migrate to cleaner areas. The authors evaluated this avoidance behavior to measure chemical stress and determine if biochar can restore soil habitability.

The findings showed that individual exposure to copper or glyphosate triggers a strong concentration-dependent avoidance response in earthworms. In soil treated with copper alone at concentrations between fifty and two hundred milligrams per kilogram, earthworm avoidance increased from forty percent to eighty-seven percent. Similarly, exposure to glyphosate alone at rates from twenty-five to one hundred milligrams per kilogram caused avoidance between forty percent and sixty percent. Higher chemical concentrations crossed critical habitability thresholds, demonstrating that single contaminants rapidly degrade soil habitat quality and force earthworms to flee.

Combining copper and glyphosate produced even more severe toxic impacts than single chemical exposures. In mixed contamination treatments, earthworm avoidance climbed to rates between sixty percent and one hundred percent. At the highest combined chemical levels, all earthworms fled the contaminated soil entirely. This amplified response stems from chemical interactions, as glyphosate chelates copper ions while copper inhibits microbial degradation of glyphosate. These interactions increase pollutant mobility and persistence, creating a harsher soil environment for beneficial organisms.

To mitigate this environmental damage, the researchers tested adding a one percent biochar amendment made from forestry residues. Biochar significantly improved soil conditions, reducing earthworm avoidance by twenty-nine percent in moderate chemical mixtures and twenty-seven percent in the highest chemical mixtures. This porous, carbon-rich material binds copper through surface complexation and absorbs glyphosate onto its porous surfaces, effectively trapping both contaminants and reducing their bioavailability in soil.

Overall, the study demonstrates that biochar amendment offers a practical solution for reducing agrochemical toxicity and protecting vital soil fauna. While future field studies in natural soils will help confirm long-term outcomes, biochar shows strong potential for restoring degraded agricultural land and supporting sustainable soil management.

Source: Sousa, J. R., Matos, C., Azevedo, T., Nascimento Gonçalves, E., Rajput, V. D., Singh, A., Ghazaryan, K., Saraiva, F., Zhang, T., & Singh, R. K. (2026). Mitigating the effects of copper and commercial glyphosate formulations with biochar: insights from Eisenia fetida avoidance assays. Biochar X, 2, 2015.