Study of the saturated hydraulic conductivity by falling–head method for different soil types amended with different biochar fraction size

Saturated hydraulic conductivity is an important soil property related to soil water regime. Generally, loam soil has a convenient moisture regime. However, if this type of soil is gradually drying out, its moisture regime may change for the worse. Our task is therefore to search for methods to increase the hydraulic conductivity of the loamy soils. In contrast, one of the goals of sandy soil management is slowing down flow velocity. In our research, we focused on the effect of biochar particle size on saturated hydraulic conductivity changes in three different soil types. The soils were selected based on their textures – sandy, silt loam and silty clay. Our results confirmed that addition of biochar with particle size <125 µm produced from paper fiber sludge and grain husks significantly (p<0.05) reduced saturated hydraulic conductivity in sandy soil by approximately 61% compared to control with sandy soil. Further, the results indicated that biochar with a fraction size >2 mm effectively increased the saturated hydraulic conductivity of silt loam soil by approximately 165% compared to pure silt loam soil. The difference was also statistically significant (p<0.05). Biochar amendment to the finest textured soil used in this study (silty clay) also increased the saturated hydraulic conductivity of the soil. The biochar with a fraction size of 125 µm–2 mm and >2 mm significantly (p<0.05) increased the saturated hydraulic conductivity by approximately 629% and 1063%, respectively when compared to pure silty clay soil.