Evaluation of the changes induced by gasification biochar in a peat-sand substrate

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 re- spirometry 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.