Biochar shows promise in unlocking soil phosphorus and improving global crop productivity

Phosphorus is essential for plant growth, yet much of the phosphorus in soils worldwide remains locked in forms that crops cannot use. A new review study highlights how biochar, a carbon-rich material derived from biomass, could play a key role in improving phosphorus availability and boosting agricultural sustainability.

“Phosphorus is a limiting nutrient in many ecosystems, and improving its availability is critical for food security,” said the study’s corresponding author. “Our work shows that biochar can provide both immediate and long-term solutions to this challenge.”

The study, published in Biochar, systematically analyzed research from the past decade to understand how biochar influences soil phosphorus dynamics. The authors reviewed thousands of studies and identified clear trends showing that biochar application generally increases the amount of plant-available phosphorus in soil.

Phosphorus fertilizers are widely used in agriculture, but they are often inefficient. Only a small fraction is absorbed by crops, while the rest can accumulate in soils or be lost to water systems, contributing to environmental pollution. In addition, global phosphorus reserves are finite, raising concerns about future supply.

Biochar offers a promising alternative. Produced by heating organic materials such as crop residues or wood under low oxygen conditions, biochar has unique physical and chemical properties. Its porous structure, high surface area, and nutrient content allow it to interact with soil in multiple beneficial ways.

The review found that biochar can directly add phosphorus to soils, depending on the type of feedstock used. For example, biochar derived from manure tends to contain higher phosphorus levels than biochar made from plant materials. At the same time, biochar can also indirectly improve phosphorus availability by altering soil properties.

One key mechanism involves soil chemistry. Biochar can increase soil pH, reduce phosphorus fixation by metals such as iron and aluminum, and promote the release of phosphorus into forms that plants can absorb. It also enhances adsorption and desorption processes, helping soils retain nutrients while still making them accessible when needed.

Physical changes to soil also play a role. The porous structure of biochar improves soil aeration and water retention, while providing surfaces for nutrient exchange. These changes can reduce nutrient loss and support more efficient nutrient cycling.

Biological processes are equally important. Biochar creates a favorable environment for soil microorganisms, including bacteria and fungi that help release phosphorus from organic and mineral sources. By stimulating microbial activity, biochar further enhances the transformation of phosphorus into plant-available forms.

However, the study emphasizes that the effects of biochar are not uniform. Factors such as soil type, biochar production temperature, feedstock, and application rate all influence outcomes. For instance, biochar tends to be more effective in acidic soils, while its impact in alkaline soils may require modification or combination with other treatments.

“Biochar is not a one-size-fits-all solution,” the authors noted. “Its performance depends on how it is produced and how it is applied. Tailoring biochar to specific soil conditions is essential for achieving the best results.”

Overall, the findings suggest that biochar could become an important tool in sustainable agriculture. By improving phosphorus efficiency, it may reduce reliance on chemical fertilizers, enhance crop yields, and mitigate environmental risks.

As global demand for food continues to rise, innovations like biochar offer new pathways to balance productivity with environmental stewardship.

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Journal Reference: Zhang, L., Chang, L., Liu, H. et al. Biochar application to soils can regulate soil phosphorus availability: a review. Biochar 7, 13 (2025).   

https://doi.org/10.1007/s42773-024-00415-1   

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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. 

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