Sulfur-modified biochar helps rice overcome vanadium pollution, study finds

A new study published in Biochar reports that sulfur-modified wheat straw biochar can dramatically reduce the toxic effects of vanadium contamination in rice, offering a promising and sustainable strategy to protect global food production in polluted regions. Vanadium is a heavy metal increasingly found in agricultural soils due to mining, smelting, fertilizer overuse, and wastewater irrigation. Even moderate exposure can stunt plant growth, damage photosynthesis, and impair the antioxidant defenses that keep crops healthy.

Researchers from Hainan University and collaborating institutions tested whether sulfur-modified biochar could help rice seedlings tolerate vanadium stress more effectively than standard biochar. Their findings show that sulfur modification greatly enhances the ability of biochar to protect plants, reduce metal uptake, and restore vital physiological processes.

“Vanadium contamination is rising in many agricultural regions, and farmers urgently need solutions that are both effective and affordable,” said senior author Zhiqiang Zhu. “Our results show that sulfur-modified biochar not only reduces vanadium accumulation in rice but also strengthens the plant’s own defense systems. This offers a path toward cleaner soils and healthier crop production.”

Significant improvements in plant growth and physiology

When rice seedlings were exposed to vanadium, their shoot and root growth dropped sharply, chlorophyll pigments declined, and photosynthesis was severely impaired. However, adding sulfur-modified biochar to the growing solution reversed much of this damage.

Compared to vanadium-stressed plants, those treated with sulfur-modified biochar showed:

• A 61 percent increase in shoot fresh weight

• A 63 percent increase in root length

• A 66 percent increase in chlorophyll a and substantial increases in chlorophyll b and carotenoids

• Major improvements in photosynthetic rate, stomatal conductance, and transpiration

The treated plants also exhibited stronger root systems with greater surface area and more branching, which supported better nutrient uptake and resilience under stress.

Lower vanadium accumulation and reduced oxidative damage

One of the most important findings is that sulfur-modified biochar sharply reduced the amount of vanadium reaching plant tissues. Compared to untreated stressed plants, vanadium levels fell by 58 percent in shoots and 44 percent in roots.

This reduction helped prevent the buildup of harmful reactive oxygen species and lipid peroxidation products that otherwise damage cell membranes. Levels of hydrogen peroxide, superoxide, and malondialdehyde were all significantly lower in plants that received sulfur-modified biochar.

At the same time, key antioxidant enzymes including superoxide dismutase, catalase, glutathione peroxidase, and glutathione S transferase increased by as much as 100 percent or more. These enzymes are essential for detoxifying reactive molecules produced during metal stress.

Strengthening genetic defenses

The study also found that sulfur-modified biochar boosted the expression of genes associated with stress tolerance, antioxidant activity, and the glyoxalase system, which helps detoxify methylglyoxal, another damaging molecule produced under stress. Several genes doubled in expression or more, indicating a strong physiological response triggered by the biochar treatment.

A sustainable approach for polluted farmlands

Because wheat straw is abundant and agricultural waste is often burned or discarded, converting it into sulfur-modified biochar offers both environmental and economic benefits. The authors note that this approach aligns with sustainable agriculture goals by recycling waste materials while improving soil and crop health.

“Our work provides a practical foundation for using sulfur-modified biochar to safeguard rice production in contaminated regions,” said first author Muhammad Mohsin Altaf. “Future field testing will help determine how this strategy can be scaled up for real-world farming.”

The researchers plan to further investigate the molecular mechanisms behind the biochar’s enhanced metal binding and explore long-term performance under field conditions.

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Journal Reference: Altaf, M.M., Ashraf, S., Khan, M.Q.N. et al. Effectiveness of sulfur-modified wheat straw biochar in alleviating vanadium stress in rice: impacts on growth, photosynthesis, and redox regulation. Biochar 7, 71 (2025). 

https://doi.org/10.1007/s42773-025-00462-2  

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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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