Biochar in growing media for fruit crops: Agronomic performance and implications for substrate formulation

The increasing need for sustainable alternatives to peat-based growing media has intensified research on biochar as a component of horticultural substrates. However, its agronomic performance remains highly variable across crops, substrate formulations, and experimental conditions, limiting its consistent application in soilless cultivation systems. This study provides a structured synthesis of the literature on biochar use in growing media, with particular emphasis on fruit crops, including grapevine, citrus, and berries. A combined approach was adopted, integrating large-scale bibliographic analysis with targeted agronomic evaluation to identify major research domains and extract crop-relevant evidence. A broad corpus of publications was mapped using text mining and clustering techniques, followed by expert-based screening and critical assessment of studies specifically addressing fruit crop production. The results indicate that biochar performance in growing media cannot be explained solely by substitution rate, but depends primarily on its functional role within substrate formulations and its interactions with crop-specific requirements and substrate physicochemical properties. Across the reviewed fruit-crop studies, low to intermediate biochar inclusion rates were more frequently associated with neutral or positive plant responses than high replacement rates, whereas higher proportions were associated with greater variability and, in some cases, negative effects depending on biochar characteristics and experimental context. This pattern should be interpreted descriptively rather than as a quantitatively estimated dose–response relationship. These findings support a shift from substitution-based approaches toward a formulation-oriented perspective, in which biochar is considered a functional component of engineered growing media. This framework provides a basis for improving the design and management of sustainable substrate systems in horticultural production.