Biochar offers powerful solution to restore acidic soils and boost agricultural sustainability
image: The key role of biochar in amending acidic soil: reducing soil acidity and improving soil acid buffering capacity
Credit: Shaowen Liu, Baiting Cen, Zening Yu, Rongliang Qiu, Ting Gao & Xinxian Long
A growing body of research highlights a global agricultural challenge that often goes unnoticed beneath our feet: soil acidification. Affecting billions of hectares worldwide, acidic soils reduce crop productivity, disrupt soil ecosystems, and threaten long-term food security. Now, a new review study sheds light on how biochar, a carbon-rich material derived from biomass, could provide an effective and sustainable solution.
“Soil acidification is a silent but widespread problem that undermines both crop yields and environmental health,” said the study’s corresponding author. “Our work shows that biochar can not only reduce soil acidity but also strengthen the soil’s natural resistance to future acidification.”
Acidic soils develop when hydrogen ions and aluminum accumulate, often due to natural processes such as rainfall and mineral weathering, as well as human activities like excessive fertilizer use. These changes can leach essential nutrients such as calcium and magnesium, increase toxic metal availability, and disrupt microbial communities critical for soil health.
Traditionally, farmers have relied on lime to neutralize acidic soils. While effective in the short term, lime has several drawbacks, including limited impact on deeper soil layers and a tendency for soils to become acidic again over time. Biochar offers a promising alternative.
Produced by heating organic materials such as crop residues under low-oxygen conditions, biochar is alkaline, porous, and rich in functional chemical groups. These properties enable it to neutralize acidity directly and improve soil structure.
The study explains that biochar works through several mechanisms. First, it acts similarly to lime by neutralizing excess hydrogen ions, raising soil pH. Second, it releases beneficial base cations such as calcium, potassium, and magnesium, which replace acidic ions in the soil. Third, its surface contains oxygen-containing functional groups that can bind harmful aluminum, reducing its toxicity to plants. Finally, biochar enhances the soil’s acid buffering capacity, meaning the soil becomes more resistant to future pH changes.
This buffering effect is particularly important. While many soil treatments provide temporary relief, biochar helps stabilize soil chemistry over longer periods. By improving buffering capacity, it slows the rate at which soils become acidic again, offering a more durable solution.
The researchers also found that the effectiveness of biochar depends on both the material itself and the soil it is applied to. Biochar produced at higher temperatures or from certain feedstocks tends to contain more alkaline components, making it more effective. Meanwhile, soils that are strongly acidic or have low buffering capacity benefit the most from biochar amendments.
However, the study also notes that biochar is not a one-size-fits-all solution. Over time, biochar can undergo aging processes in the soil, which may reduce its alkalinity. In addition, ongoing agricultural practices such as nitrogen fertilization can continue to drive acidification. Understanding these dynamics will be essential for optimizing long-term soil management strategies.
“Our findings emphasize that biochar should be tailored to specific soil conditions and used as part of an integrated management approach,” the authors noted.
Beyond improving soil health, biochar offers additional environmental benefits. It can store carbon in soils for long periods, helping mitigate climate change, while also enhancing nutrient retention and reducing pollution from agricultural runoff.
As global demand for sustainable agriculture grows, biochar is emerging as a versatile tool that addresses both productivity and environmental challenges. By restoring soil balance and resilience, it may play a key role in securing the future of food systems worldwide.
===
Journal Reference: Liu, S., Cen, B., Yu, Z. et al. The key role of biochar in amending acidic soil: reducing soil acidity and improving soil acid buffering capacity. Biochar 7, 52 (2025).
https://doi.org/10.1007/s42773-025-00432-8
===
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.