Agronomic performance, essential oils and hydrodistillation wastewaters of Lavandula angustifolia grown on biochar-based substrates

The dramatic increase of peat use for agricultural purposes and the consequent depletion of peatlands has resulted in an increasing environmental concern about peat extraction and in a continuous search for sustainable substitutes. In order to find an efficient alternative to peat as substrate component for horticultural industry, a study was accomplished to assess the influence on Lavandula angustifolia Miller potted plants grown in a peat-based substrate amended with increasing amount of conifer wood biochar: 0, 25, 50, 75 and 100 % (by volume). Higher values of plant height, leaf area, leaves and flowers production were recorded in potted lavenders grown in substrates with a biochar content ranging from 25 % to 75 %; at a visual-quality evaluation no significant differences were observed among substrates on the general aesthetic effect of the plants. The aforesaid five different substrates tested did not significantly affect the leaf dry weight and the root-to-shoot ratio. The biochar amendment of peat-based substrates, even at high rates (75 % or 100 %), did not influence lavender essential oil (EO) quality, its chemical profile and antioxidant activity. The radical scavenging activities of EO and hydro-distilled wastewaters were also detected. Main results from our study seem to suggest that a conifers wood biochar may be efficiently used as substrate alternative to peat to grow Lavandula angustifolia plants for EO production.