Global study reveals biochar’s powerful potential to combat soil acidification
image: The potential of biochar to mitigate soil acidification: a global meta-analysis
Credit: Nanhai Zhang, Jiamin Xing, Lianjun Wei, Chang Liu, Wenjing Zhao, Zihan Liu, Yuhao Wang, Enke Liu, Xiaolong Ren, Zhikuan Jia, Ting Wei, Kadambot H. M. Siddique & Peng Zhang
Soil acidification is quietly threatening agricultural productivity worldwide, reducing crop yields and degrading soil health. Now, a new global study shows that biochar, a carbon-rich material made from agricultural waste, could offer a widely effective and sustainable solution.
In a comprehensive meta-analysis published in Biochar, researchers analyzed data from 232 studies across different climates, soil types, and farming systems. The results provide one of the most detailed assessments to date of how biochar influences soil acidity and when it works best.
“Soil acidification is a growing global challenge, especially in regions with intensive agriculture,” said the study’s corresponding author. “Our findings show that biochar can significantly improve soil conditions, but its effectiveness depends on both environmental and management factors.”
The research team evaluated 1,460 paired observations comparing soils treated with and without biochar. On average, biochar increased soil pH by 5.59 percent, indicating a meaningful reduction in soil acidity. However, the study also found that biochar does not work uniformly in all conditions, highlighting the importance of context-specific application.
Biochar improves soil pH through several mechanisms. It contains alkaline compounds and mineral ash that neutralize acidity, while its surface functional groups can bind hydrogen ions, reducing acidity in soil solutions. Unlike traditional lime treatments, biochar can also provide longer-lasting effects and additional environmental benefits, such as carbon sequestration and improved soil structure.
The study identified several key factors that determine how well biochar performs. One of the most important is the initial condition of the soil. Acidic soils showed the greatest improvement, while neutral or alkaline soils experienced little or no benefit. Similarly, soils with high buffering capacity, measured as cation exchange capacity, were less responsive to biochar amendments.
Climate also plays a major role. The researchers found that biochar was more effective in regions with higher temperatures and rainfall. These conditions tend to accelerate soil acidification processes, making the liming effect of biochar more pronounced. As a result, paddy fields, which are typically wetter environments, showed greater improvements in soil pH than dryland agricultural systems.
The properties of the biochar itself are equally critical. Biochar produced at moderate temperatures and with higher intrinsic pH values delivered stronger results. Application rate also mattered, with larger amounts generally leading to greater improvements in soil pH. In addition, combining biochar with organic fertilizers enhanced its effectiveness compared to pairing it with synthetic fertilizers.
Despite its overall benefits, the study emphasizes that biochar is not a one-size-fits-all solution. In some cases, particularly in already alkaline soils, biochar application could have little effect or even slightly reduce soil pH. The researchers also noted that the positive effects of biochar may diminish over time, especially as nutrients are taken up by crops or leached from the soil.
“Our study highlights that biochar is a promising tool, but it must be applied strategically,” the authors noted. “Understanding local soil conditions, climate, and management practices is essential to maximize its benefits.”
The findings provide important guidance for farmers, land managers, and policymakers seeking sustainable ways to restore degraded soils and maintain long-term agricultural productivity. As interest grows in climate-smart agriculture and circular bioeconomy solutions, biochar could play a key role in addressing both soil health and carbon management challenges.
By offering a globally validated perspective, this study lays the groundwork for more targeted and efficient use of biochar in agriculture, helping to turn agricultural waste into a valuable resource for soil restoration.
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Journal Reference: Zhang, N., Xing, J., Wei, L. et al. The potential of biochar to mitigate soil acidification: a global meta-analysis. Biochar 7, 49 (2025).
https://doi.org/10.1007/s42773-025-00451-5
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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.