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.
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