New method improves how scientists measure water behavior in biochar-amended soils
A new study has introduced a more accurate way to evaluate how biochar interacts with water, offering important insights for agriculture, soil management, and environmental sustainability.
Biochar, a carbon-rich material produced from biomass, is widely used to improve soil quality and water retention. However, understanding how biochar affects soil water behavior has long been challenging due to limitations in existing measurement methods.
Researchers have now developed a new approach called the dynamic contact angle method, which provides a more realistic assessment of how water interacts with biochar and biochar-amended soils over time. The findings were recently published in Biochar.
“Traditional methods only capture a snapshot of water behavior, but water interactions with biochar are dynamic,” said one of the study’s corresponding authors. “Our method allows us to observe how these interactions evolve, which leads to a more accurate understanding of soil water processes.”
Conventional techniques typically rely on two indicators: contact angle and water droplet penetration time. While contact angle measures how water initially sits on a surface, penetration time reflects how long it takes for water to be absorbed. These two methods often produce conflicting results, making it difficult to determine whether a material is truly water-repellent.
To resolve this issue, the research team tracked how the contact angle changes over time as a water droplet spreads and diffuses. By monitoring this process over 90 seconds, they introduced a new classification system for material behavior, including a newly defined category called “pseudo-hydrophobicity.”
This category describes materials that initially appear water-repellent but gradually become wettable as water spreads across their surface. According to the study, failing to account for this transition can lead to overestimating hydrophobicity.
“Our findings show that some materials previously classified as hydrophobic are actually only temporarily resistant to water,” the authors explained. “Recognizing pseudo-hydrophobicity helps reconcile inconsistencies between existing measurement methods.”
The researchers tested their approach on a wide range of materials, including 17 standard substances and 18 different types of biochar produced from agricultural residues, forestry byproducts, and household waste. The results demonstrated that the dynamic method consistently provided a more reliable evaluation of water behavior.
The study also explored how biochar affects soil over time. In controlled experiments lasting 90 days, most biochar types increased soil water repellency immediately after application. However, this effect tended to decrease with time, likely due to aging processes, microbial activity, and chemical changes on the biochar surface.
Importantly, the results showed that both the type of biochar and its application rate influence soil water behavior. Higher application rates generally led to stronger water repellency, while biochar produced at lower temperatures tended to be more hydrophobic due to its surface chemistry.
The researchers emphasize that understanding these dynamics is crucial for optimizing biochar use in agriculture, particularly in dry and semi-arid regions where water management is critical.
“This work provides a new tool for predicting how biochar will perform in real-world conditions,” the authors said. “It can help guide the design of biochar materials and improve strategies for soil water management.”
By offering a clearer and more comprehensive way to evaluate water interactions, the dynamic contact angle method could support the development of more effective soil amendments and sustainable agricultural practices.
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Journal Reference: Jing, W., Su, M., Yang, K. et al. Dynamic contact angle as a new metric for the water repellency evaluation of biochar-amended soil. Biochar 8, 38 (2026).
https://doi.org/10.1007/s42773-025-00555-y
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About Biochar
Biochar (e-ISSN: 2524-7867) 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.
Follow us on Facebook, X, and Bluesky.
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Biochar, a carbon-rich material produced from biomass, is widely used to improve soil quality and water retention. However, understanding how biochar affects soil water behavior has long been challenging due to limitations in existing measurement methods.
Researchers have now developed a new approach called the dynamic contact angle method, which provides a more realistic assessment of how water interacts with biochar and biochar-amended soils over time. The findings were recently published in Biochar.
“Traditional methods only capture a snapshot of water behavior, but water interactions with biochar are dynamic,” said one of the study’s corresponding authors. “Our method allows us to observe how these interactions evolve, which leads to a more accurate understanding of soil water processes.”
Conventional techniques typically rely on two indicators: contact angle and water droplet penetration time. While contact angle measures how water initially sits on a surface, penetration time reflects how long it takes for water to be absorbed. These two methods often produce conflicting results, making it difficult to determine whether a material is truly water-repellent.
To resolve this issue, the research team tracked how the contact angle changes over time as a water droplet spreads and diffuses. By monitoring this process over 90 seconds, they introduced a new classification system for material behavior, including a newly defined category called “pseudo-hydrophobicity.”
This category describes materials that initially appear water-repellent but gradually become wettable as water spreads across their surface. According to the study, failing to account for this transition can lead to overestimating hydrophobicity.
“Our findings show that some materials previously classified as hydrophobic are actually only temporarily resistant to water,” the authors explained. “Recognizing pseudo-hydrophobicity helps reconcile inconsistencies between existing measurement methods.”
The researchers tested their approach on a wide range of materials, including 17 standard substances and 18 different types of biochar produced from agricultural residues, forestry byproducts, and household waste. The results demonstrated that the dynamic method consistently provided a more reliable evaluation of water behavior.
The study also explored how biochar affects soil over time. In controlled experiments lasting 90 days, most biochar types increased soil water repellency immediately after application. However, this effect tended to decrease with time, likely due to aging processes, microbial activity, and chemical changes on the biochar surface.
Importantly, the results showed that both the type of biochar and its application rate influence soil water behavior. Higher application rates generally led to stronger water repellency, while biochar produced at lower temperatures tended to be more hydrophobic due to its surface chemistry.
The researchers emphasize that understanding these dynamics is crucial for optimizing biochar use in agriculture, particularly in dry and semi-arid regions where water management is critical.
“This work provides a new tool for predicting how biochar will perform in real-world conditions,” the authors said. “It can help guide the design of biochar materials and improve strategies for soil water management.”
By offering a clearer and more comprehensive way to evaluate water interactions, the dynamic contact angle method could support the development of more effective soil amendments and sustainable agricultural practices.
===
Journal Reference: Jing, W., Su, M., Yang, K. et al. Dynamic contact angle as a new metric for the water repellency evaluation of biochar-amended soil. Biochar 8, 38 (2026).
https://doi.org/10.1007/s42773-025-00555-y
===
About Biochar
Biochar (e-ISSN: 2524-7867) 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.
Follow us on Facebook, X, and Bluesky.
END