Olive tree pruning derived biochar increases glucosinolate concentrations in broccoli

Biochar has attracted great attention in the soil scientific community for its interaction with different biogeochemical cycles and its potential environmental and agronomical benefits. However, there is only limited information about its effect on plant secondary metabolism. In this manuscript, a biochar produced from olive tree pruning by slow pyrolysis at 600 °C was selected to analyze its impact on the concentration of the health-promoting compounds glucosinolates (GLSs) in broccoli. The biochar was applied as soil amendment, alone or combined with organic and mineral fertilization, in a broccoli cultivar in the field. We found that this particular biochar caused an enrichment in GLSs concentration in broccoli amended with biochar alone. Meanwhile, the fertilized treatments caused a decrease in the GLSs concentration in broccoli inflorescence, particularly mineral fertilization originated the lowest concentration of neoglucobrassicin and glucoraphanin. When biochar was combined with mineral fertilization it increased the concentration of GLS to similar levels as the untreated plants, probably as a physiological response of the plant to the enhanced physicochemical properties of biochar amended soils. These findings highlight the importance of agronomical practices in achieving a balance between a good performance in production and the presence of beneficial phytochemicals.