Effect of straw and wood biochar application on growth of Miscanthus × giganteus on marginal soil: a meso-scale study with shock short-term screening

The effect of biochar (Bc) application on marginal soil fertility and growth of Miscanthus × giganteus ( M × g ) was investigated in a greenhouse-based short-term mesocosm experiment. Straw (SBc) and wood-based (WBc) biochars were added to poor class marginal soil (C = 0.5 %) in 5 volumetric ratios (0, 1, 2.5, 5, 10, 15 % v/v). The composition and nanostructure of SBc and WBc were assessed in reference to European Biochar Certificate Guidelines. Both SBc and WBc presented alkaline pH, high fixated carbon content (>70 %), and H/C = 0.05, that suggest good fertilisation potential. Straw Bc contained greater amount of bioavailable macro and microelements (especially N, P, K, Mg, Ca, Fe) with acceptable level of heavy metal contents according to EBC-Agro (2012–2023), except Cr (100 ppm). The growth, photosynthetic rates (gas exchange, chlorophyll, specific leaf area), and root tissue anatomy were evaluated. Miscanthus presented average height growth rate around control treatments (31.22 ± 6.2 mm/day). After short term vegetation M × g achieved a mean height of roughly 1.6 m, with maximal growth found in 1 % and 2.5 % for both Bc. Photosynthetic rates reflected proper plant feedback achieved in Bc supplemented soil. At increasing ratios of Bc, the height was significantly reduced, but there was no effect on photosynthetic metabolism and biomass production. M × g 's response to shock short-term Bc application into soil resulted in changes of aerenchyma formation. Positive effect on soil oxygenation was discovered for SBc, leading to decrease of aerenchyma spaces, while WBc application (except 15 % dose) caused negative effect on plant nutrition, resulting in an increase in aerenchyma spaces. • M. giganteus planting on marginal soil amended with straw and wood biochars. • Straw biochar with greater amount of bioavailable macro- and microelements. • C fix >70 % and H/C = 0.05 suggest good fertilization potential of both biochars. • Root aerenchyma changes suggests straw biochar enhancement in soil oxygenation. • Heigh growth rate inhibition in biochar doses greater than 5 % (v/v).