Effect of biochar on the unsaturated hydraulic conductivity of two amended soils
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School of Agricultural Engineering, Instituto Tecnológico de Costa Rica, 159-7050 Cartago, Costa Rica
Institute for Plant Nutrition and Soil Science, Christian-Albrechts University Kiel, Hermann Rodewaldstr. 2, 24118 Kiel, Germany
Publication date: 2018-07-10
Int. Agrophys. 2018, 32(3): 373-378
Water and solute transports in the vadose zone depend on the distribution, size, shape and configuration of the pores. They affect the soil hydraulic properties and, consequently, the directly related processes such as water storage, infiltration, groundwater recharge, and also erosion and runoff. Soils amended with biochar are prompt to improve their physical and hydraulic properties. Biochar addition alters not only porosity, the water retention pattern and the derived pore distribution, but also the hydraulic conductivity under saturated and unsaturated conditions. In our work, two different doses (2.5 and 5% dry wt.) were added to two textured soils (sand and sandy loam). The unsaturated hydraulic conductivity and saturated hydraulic conductivity were measured under laboratory conditions. The obtained results show the positive effect of biochar on the hydraulic functions. For the sandy soil, the higher the dose of biochar, the more constant and relatively higher is the hydraulic conductivity up to - 40 kPa. At less negative matric potentials (< -10 kPa), the unamended sandy loam soil showed a slightly higher unsaturated hydraulic conductivity, compared to the amended soils. These results underline that biochar addition enhances the transport of water under unsaturated conditions by reducing the formation of larger pores while also intensifying the finer inter-particle pore formation.
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