Coniferous wood biochar as substrate component of two containerized Lavender species: Effects on morpho-physiological traits and nutrients partitioning

Peat moss continued to be, though the exploitation of peatlands due to the peat extraction, the most important and used growing substrate in the nursery production of containerized ornamental plants. Biochar, the byproduct of the pyrolysis technology for bio-energy process from organic feedstocks, has been recently demonstrated a promising replacement substitute for peat in ornamentals production. An experiment was carried out in order to evaluate the differences on growth, ornamental quality and nutrients partitioning of two Lavender species (Lavandula angustifolia and L. dentata) grown in a peat-based growing substrate amended with coniferous wood biochar at 0%, 25 %, 50 % or 75 % (by volume). Increasing biochar content of growing substrates resulted in an increase of several chemical and physical properties such as electrical conductivity, pH, bulk density and total porosity and in a decrease of water retention capacity as well as in nutrients availability (P, Ca and Mg). Higher biochar percentages in the substrate negatively affected growth pattern and physiological traits of the potted plants, due to suboptimal conditions of growing substrates. Lavenders grown with 25 % biochar showed similar growing and qualitative response in terms of number of leaves, root length, biomass production and biomass water use efficiency, compared to those cultivated with 0% biochar, due to an enhanced SPAD index, photosynthetic pigments biosynthesis and leaf nutritional status (higher nitrate, P and K). Overall, our experimental data demonstrated that a peat-based substrate amended with 25 % of coniferous wood biochar could be adopted as a sustainable production system for containerized lavenders, with no negative effects on plant growth and ornamental quality.