Modeling the hydraulic conductivity of two soils amended with biochars using a statistical-physical model

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A b s t r a c t.This study aimed to predict the effect of biochars (from woodchips, rice straw, and manure processed at temperatures from 300 to 700°C) on hydraulic conductivity, volumes of variously sized capillaries (from 360.4 to 0.24 µm radius), and equivalent capillary length of sandy and loamy soils using the statistical-physical model.The model analyzes the connections between soil and biochar and spaces occupied by water and air.The biochars decreased the predicted hydraulic conductivity at the matric potentials from -1 to around -70 cm H 2 O by 9 to 25% and increased by 1.6 to 19% at a drier range of potential from around -500 to -15 000 cm H 2 O in the sandy soil and increased in the loamy soil across the whole potential range.The greatest effect on the hydraulic conductivity had biochars from the rice straw in sandy soil and woodchips in loamy soil.The biochars generally increased the volumes of all capillaries in the sandy soil.They decreased the volumes of larger capillaries (360.4-3.6 µm radius) and increased that of capillaries of 0.53 µm radius in the loamy soil.All biochars typically decreased the equivalent capillary length in the sandy soil and increased in the loamy soil.