Effects of biochar on water retention and matric suction of vegetated soil

Biochar is the pyrolysed biomass which has been used as a soil amendment to improve plant performance. This study aims to investigate the effects of biochar–plant interaction on soil water retention and matric suction in silty sand (SM). In total, four soil conditions, namely soil with and without tree (Schefflera heptaphylla), biochar-amended soil (BAS) with and without tree, were subjected to drying. Three replicates were considered for each vegetated soil. By adding 10% (v/v) of biochar, the optimum water content of soil increased from 12 to 17%, while the maximum dry density decreased from 1890 to 1740 kg/m3. For both bare and vegetated soils with biochar, desorption rates of soil water-retention curves were smaller than those without biochar, while there were almost no changes in air-entry value (AEV). Biochar reduced matric suction in bare soil by 35–70% and in vegetated soil by 12–36%.