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/m(3). 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%.