Biochar shifts balance between hydrophilic and lipophilic molecules in root exudates

The current study investigated the impact of biochar on root exudate chemistry and characterized exudate molecule abundance as a function of biochar application rates. In exudates trickled over biochar, organic oxygen-rich compounds were the most common molecules stemming from biochar, comprising 67 % of the abundance of biochar-derived compounds. Eighty percent of these compounds stemming from biochar were hydrophilic. On the other hand, biochar-retained molecules were mostly lipophilic (87 %) and consisted mainly of lipid-related compounds (52 %). In addition, root-exuded molecules with ≥ 20 aliphatic-carbon atoms were retained by biochar (representing 44 % of all retained molecules) but were not released from biochar. These findings indicate that biochar can increase the hydrophilic:lipophilic balance of root exudates. In soil, this change could influence the spatial heterogeneity of dissolved organic matter and the role of root exudates in modulating plant-plant and plant-microbe interactions.