Biochar and beneficial microbes team up to protect crops and restore cadmium contaminated soils

Soil contamination by cadmium is a growing global challenge that threatens food safety, agricultural productivity, and environmental health. Cadmium is a highly toxic heavy metal that accumulates easily in soils and crops, entering the food chain and posing long term risks to humans and ecosystems. A new study shows that a simple combination of biochar and beneficial microorganisms can significantly reduce cadmium stress in crops while restoring soil health.

Researchers from Henan Agricultural University and international partners report that adding biochar together with the beneficial fungus Trichoderma to contaminated soils improved plant growth, reduced cadmium uptake, and enhanced soil microbial diversity. Their findings were published in the journal Biochar.

The research focused on tobacco, a crop known to readily accumulate cadmium and often grown in contaminated regions. Using controlled pot experiments, the team compared plants grown in clean soil, cadmium contaminated soil, and contaminated soil amended with biochar alone or biochar combined with Trichoderma. Biochar is a carbon rich material produced by heating agricultural waste under low oxygen conditions and is increasingly recognized for its soil improvement potential.

Cadmium stress sharply reduced photosynthesis, biomass production, and soil enzyme activity. However, when biochar was added, plants recovered much of their photosynthetic capacity. The greatest improvements occurred when biochar was combined with Trichoderma, a fungus widely used in agriculture for promoting plant growth and resilience.

“Cadmium severely suppresses plant physiological processes, especially photosynthesis,” said corresponding author Tianbao Ren. “We found that biochar can partially reverse these effects, but when biochar and beneficial microbes work together, the benefits are much stronger and more consistent.”

Plants grown with both biochar and microbes showed higher photosynthetic efficiency, greater dry matter accumulation, and improved resistance to cadmium toxicity. Importantly, the treatment also limited the movement of cadmium from roots to leaves, which is critical for reducing contamination in harvested plant tissues.

The soil itself also benefited from the combined amendment. Cadmium contamination reduced soil enzyme activities and microbial biomass, indicators of poor soil health. Biochar restored these functions, while the addition of Trichoderma further increased microbial diversity and promoted beneficial microbial groups associated with nutrient cycling and soil stability.

“Soil is a living system, not just a physical medium,” said co corresponding author Su Shiung Lam. “Our results show that rebuilding the soil microbial community is key to long term remediation. Biochar provides a habitat, and microorganisms bring the biological functions needed for recovery.”

The study highlights a synergistic mechanism. Biochar adsorbs cadmium and reduces its bioavailability, while its porous structure creates favorable conditions for microbial colonization. Trichoderma further enhances nutrient availability, enzyme activity, and plant stress tolerance, leading to a healthier soil plant system overall.

Although the experiments were conducted with tobacco, the researchers say the findings have broad implications for sustainable agriculture and soil remediation worldwide. The approach uses low cost materials, agricultural residues, and naturally occurring microorganisms, making it suitable for large scale application.

“This strategy offers a practical and environmentally friendly solution for managing cadmium contaminated soils,” Ren said. “By combining physical immobilization with biological restoration, we can protect crops, improve soil health, and reduce environmental risks at the same time.”

As cadmium pollution continues to threaten farmland globally, integrated solutions like biochar microbe systems may play a critical role in ensuring safe food production and long term soil sustainability.

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Journal Reference: Ren, T., Feng, H., Wan Mahari, W.A. et al. Biochar and microbial synergy: enhancing tobacco plant resistance and soil remediation under cadmium stress. Biochar 7, 119 (2025).   

https://doi.org/10.1007/s42773-025-00535-2  

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About Biochar

Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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