Gasification biochar represents one of the biochar types tested for agricultural needs. The aim of this study was to clarify the physico-chemical and biological changes occurring in a peat-sand substrate amended with hardwood-derived gasification biochar in the rates of 2, 4 and 20 g l^-1. The pH(H2O) of the substrate with 4 g l^-1 and 20 g l^-1 biochar was increased from 5.6 to 6.2 and 6.7, respectively. The testing of the substrate in the respirometry device showed that the increase in the biochar rate led to a decrease in the amount of CO₂ evolved at the maximum pressure drop. The continuous decrease in pressure observed in the respirometry bottles filled with pure biochar allows explaining this effect by biochar sorption activity. Addition of 2 and 4 g l^-1 biochar to the peat-sand substrate stimulated the growth of cucumbers in an 18-day pot vegetation experiment. An increase in the number of root tips and root volume with a decreasing average root diameter was shown in the presence of biochar. Stimulation of plant growth on the background of low rates of biochar requires a further study with emphasis on the specific combination of biochar, soil type, plant species, and climatic conditions.