A growing body of research suggests that combining biochar with other soil amendments such as compost, manure, or fertilizers may improve soil health more effectively than using biochar alone. A new review synthesizing field studies from around the world shows that this co-application approach can enhance soil structure, nutrient availability, and microbial activity, offering a promising strategy for sustainable land management.
Biochar is a carbon-rich material produced by heating biomass in low-oxygen conditions. It has gained attention for its ability to improve soil water retention, nutrient cycling, and long-term carbon storage. However, its performance varies widely depending on soil type, climate, and application practices. To better understand how to maximize its benefits, researchers analyzed results from 28 field studies examining biochar used alone and in combination with organic or inorganic amendments.
The analysis found that adding biochar together with other amendments improved nine out of sixteen measured soil properties compared with biochar alone. In many cases, the combined approach increased soil water content, nutrient holding capacity, and microbial activity. For example, co-application enhanced soil phosphorus levels by as much as seventy-six percent in some comparisons and improved cation exchange capacity by more than fifty percent on average.
Physical soil improvements were also evident. The combined use of biochar and amendments increased aggregate stability and hydraulic conductivity, both of which influence how water moves through soil. These changes can support better plant growth by improving aeration, reducing erosion, and strengthening soil structure.
Biological responses were equally encouraging. Several studies reported increases in microbial biomass and enzyme activities, indicators of active nutrient cycling and soil fertility. The review suggests that biochar’s porous structure may provide protective microhabitats for soil microbes while organic amendments supply the nutrients needed for microbial growth.
“Biochar alone has important benefits, but our synthesis shows that pairing it with complementary amendments can amplify its impact on soil health,” said the study’s lead author. “This combined strategy may help farmers improve soil resilience, boost nutrient efficiency, and support long-term productivity.”
The findings also highlight that not all combinations perform equally well. Biochar mixed with organic materials such as compost or manure tended to produce more consistent improvements than combinations with inorganic fertilizers alone. The effectiveness of co-application also depended on application rate, soil conditions, and climate.
Despite promising trends, the researchers emphasize that more long-term field experiments are needed. Many studies lasted only a few years, making it difficult to assess how biochar mixtures influence soil processes over decades. Understanding these long-term effects will be crucial for guiding sustainable agricultural practices and climate-smart soil management.
Overall, the review indicates that biochar co-application represents a practical pathway to strengthen soil health while potentially enhancing carbon storage and resource efficiency. As global agriculture faces pressures from climate change, land degradation, and increasing food demand, strategies that improve soil function could play a key role in building resilient farming systems.
===
Journal Reference: Adetunji, A.T., Blanco-Canqui, H. Soil health response to biochar combined with other amendments: a review. Biochar 8 , 23 (2026).
https://doi.org/10.1007/s42773-025-00531-6
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 .
Biochar
Literature review
Not applicable
Soil health response to biochar combined with other amendments: a review
6-Feb-2026