Agricultural soils are increasingly exposed to multiple pollutants as modern farming relies on repeated chemical inputs to maintain crop productivity. Copper-based fungicides are widely used in orchards, vineyards, and horticultural systems, while glyphosate-based herbicides are among the most commonly applied weed-control products worldwide. Previous studies have examined copper or glyphosate separately, but real agricultural soils often receive both contaminants within the same management cycle. This co-occurrence may alter contaminant mobility, persistence, and toxicity, creating risks that single-substance tests may underestimate. At the same time, rapid and sensitive methods are needed to assess whether soil amendments can reduce these risks before long-term damage occurs to soil organisms and ecosystem functions.
A study (DOI: 10.48130/bchax-0026-0013) published in Biochar X on 13 May 2026 by Rupesh Kumar Singh's team, Universidade de Trás-os-Montes e Alto Douro, reports that copper and glyphosate jointly intensify earthworm avoidance behavior, while biochar partly mitigates this stress by improving contaminated soil habitability.
To test these effects, the researchers used a standardized artificial soil and followed International Organization for Standardization standard 17512-1 for earthworm avoidance assays. Adult Eisenia fetida earthworms were selected as bioindicators because they are highly sensitive to changes in soil quality and play key ecological roles in organic matter turnover, aggregation, porosity, and nutrient cycling. The artificial soil was prepared from sand, kaolin, and peat, with pH and moisture adjusted to suitable test conditions. Copper was applied as copper sulfate, while glyphosate was applied as a commercial formulation. The experiment included separate treatments for copper at 0, 50, 100, and 200 mg kg−1 and glyphosate at 0, 25, 50, and 100 mg kg−1. Combined treatments paired increasing levels of both contaminants, including Gly25-Cu50, Gly50-Cu100, and Gly100-Cu200. For the two highest combined treatments, the team added 1% biochar by weight, equivalent to an agronomic amendment rate of about 20 t ha−1. Each container held uncontaminated soil on one side and test soil on the other, and 10 adult earthworms were placed along the central line. After 48 hours under controlled temperature, light, and moisture conditions, the researchers counted the earthworms in each section and calculated avoidance percentages. The results showed no stress response in the double control, confirming test validity. Copper alone produced avoidance from 40% to 87%, while glyphosate alone produced avoidance from 40% to 60%. When the two contaminants were combined, avoidance increased to 60%–100%, indicating amplified toxicity and severe loss of soil habitability at the highest mixture levels. Biochar significantly reduced avoidance in the Gly50-Cu100 and Gly100-Cu200 treatments by approximately 29% and 27%, respectively, showing partial but meaningful mitigation.
Overall, the study highlights the importance of evaluating contaminant mixtures rather than relying only on single-pollutant assessments. Copper and glyphosate may interact through metal complexation, changes in microbial degradation, and altered bioavailability, making their combined effects more harmful to soil fauna than either compound alone. Biochar did not fully restore soil quality at the highest contamination level, but it clearly reduced behavioral stress, supporting its value as a sustainable remediation tool. The authors note that future work should validate these findings in natural agricultural soils, where organic matter, minerals, microbial communities, and long-term exposure conditions may influence contaminant behavior.
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References
DOI
10.48130/bchax-0026-0013
Original Source URL
https://doi.org/10.48130/bchax-0026-0013
Funding information
Authors acknowledge the financial support by the National Funds provided by FCT (Portuguese Foundation for Science and Technology) under the project UIDB/04033/2020 (doi: 10.54499/UIDB/04033/2020), the ECONUTRI project, and the European Union Horizon Europe Innovation program under Grant Agreement No. 101081858. Financial support provided under agreement number 25IRF/2-4C002 from Higher Education and Science Committee Republic of Armenia is gratefully acknowledged.
About Biochar X
Biochar X (e-ISSN 3070-1686) is an open access, online-only journal aims to transcend traditional disciplinary boundaries by providing a multidisciplinary platform for the exchange of cutting-edge research in both fundamental and applied aspects of biochar. The journal is dedicated to supporting the global biochar research community by offering an innovative, efficient, and professional outlet for sharing new findings and perspectives. Its core focus lies in the discovery of novel insights and the development of emerging applications in the rapidly growing field of biochar science.