Effect of biochar amendment on water infiltration in a coastal saline soil

PurposeIncreasing data have shown that biochar amendment can improve soil fertility and crop production, but there is little knowledge about whether biochar amendment can improve water infiltration in saline soils. We hypothesized that biochar amendment could promote water infiltration in saline soil. The aims of this study were to evaluate the effects of biochar amendment on water infiltration and find the suitable amendment rate and particle size of biochar as a saline soil conditioner.Materials and methodsWe measured water infiltration parameters in a coastal saline soil (silty loam) amended with non-sieved biochar at different rates (0.5, 1, 2, 5, and 10%, w/w) or sieved biochar of different particle sizes (0.25mm, 0.25-1mm, and 1-2mm) at 1 and 10% (w/w).Results and discussionCompared with the control, amending non-sieved biochar at 10% significantly decreased water infiltration into the saline soil (P<0.05). In contrast, sieved biochar of 0.25mm significantly improved water infiltration capacity, irrespective of the amendment rate. Sieved biochar of 1-2mm was less effective to improve soil porosity and when amended at 10%, it even reduced the water infiltration capacity. The Philip model (R-2=0.983-0.999) had a better goodness-of-fit than the Green-Ampt model (R-2=0.506-0.923) for simulation of cumulative infiltration.ConclusionsAmending biochar sieved to a small particle size improved water infiltration capacity of the coastal saline soil compared with non-sieved biochar irrespective of the amendment rate. This study contributes toward improving the hydrological property of coastal saline soil and rationally applying biochar in the field.