Title : Meta-analysis of biochar effects on plant yield and soil nutrient dynamics across agroecological systems
Abstract:
Biochar is a carbon-rich, porous, and alkaline material produced through the pyrolysis of organic biomass. Due to its unique physicochemical properties, biochar has emerged as a promising soil amendment with the potential to enhance soil fertility, sequester carbon, and support sustainable agricultural practices. Its application is particularly beneficial in agroecosystems characterized by degraded, acidic, or nutrient-deficient soils, where conventional inputs may be less effective or environmentally taxing. In this study, we conducted a comprehensive meta-analysis to quantitatively assess the effects of biochar application on plant yield and biomass mineral composition under varying agroecological conditions. A total of 71 peer-reviewed studies were selected from an initial pool of 2,725 publications retrieved from major scientific databases, including Web of Science, Scopus, and ScienceDirect. The selection criteria were based on relevance, data quality, and the presence of comparable experimental parameters. We employed a random-effects model to account for heterogeneity across studies and used non-aggregated (raw or individual) datasets to ensure a robust statistical analysis. This positive effect is likely attributable to improvements in soil physical and chemical properties, such as enhanced soil structure, increased water-holding capacity, elevated cation exchange capacity, and greater nutrient availability. In particular, biochar was found to markedly increase soil potassium (K) levels, potentially due to the release of potassium from biochar’s ash fraction and its mineral surfaces. This enrichment can be especially advantageous in potassium-deficient soils, contributing to improved plant growth and resilience. Conversely, the analysis revealed no statistically significant effect of biochar on soil nitrogen (N) content. This outcome may stem from the inherently low nitrogen content of most biochars, coupled with the high mobility and susceptibility of nitrogen to leaching and volatilization in soil systems. These findings underscore the need for integrated nutrient management strategies when using biochar, especially in nitrogen-limited environments. Overall, this meta-analysis highlights the agronomic value of biochar, particularly for improving yield and potassium dynamics in soils. However, it also points to the importance of considering biochar’s limitations and the variability of its effects across different contexts. Future research should focus on optimizing biochar formulations, application rates, and combinations with other soil amendments to maximize its benefits while mitigating nutrient imbalances.
