Dual-scale experimental analysis: effect of biochar on lettuce growth and health

This study aimed to evaluate the effects of biochar on lettuce growth under laboratory and pilot scale greenhouses conditions integrating visual and proximal sensing monitoring approaches. Monitoring happened (i) visually, recording at harvest the number of leaves, chlorophyll content, fresh and dry biomass; and (ii) via a remote sensing system collecting multispectral data, enabling calculation of the Normalized Difference Vegetation Index (NDVI). Three different tests were performed synchronously at both scales, and the plant pathogen Fusarium oxysporum was also added at pilot scale. Overall, biochar addition increased lettuce plants’ growth and physiological performance. The results of visual monitoring were: in test 1 (Nov-Dec 2024) +39% number of leaves and +161% biomass fresh weight at laboratory scale, and +12% number of leaves and +32% biomass fresh weight at pilot scale; in test 2 (March-April 2025) +11% number of leaves and +52% biomass fresh weight at laboratory scale, and a decrease in both (− 16% and − 44%) at pilot scale; in test 3 (May-July 2025) +16% number of leaves and no variation in fresh biomass weight at laboratory scale, and +28% number of leaves and +47% fresh biomass weight at pilot scale. Chlorophyll content increased with biochar (up to +12% at laboratory scale and up to +68% at pilot scale). In some cases, plants supplemented with biochar were less affected by Fusarium wilt, although results varied according to the type of biochar and applied dosage. Overall, biochar contributed to improved plant performance in the majority of experimental scenarios, although its effects were context-dependent and influenced by scale and seasonal conditions. The integration of visual and proximal sensing supported scalable, non-destructive crop monitoring.