Soil Thermal Properties of Two Biochar Amended Soils.

Knowledge of soil thermal properties is critical for understanding the partitioning of energy and the transfer of heat and water at and near soil surfaces.  Biochar, one of three products produced from the pyrolysis process and identified as a soil amendment, may impact the partitioning of energy and the transfer heat and water near the soil surface due to changes in the physical structure of the soil.  These changes can modify soil thermal properties, which are highly dependent upon soil moisture and soil air-filled porosity.  Therefore, the objective of this study is to determine the soil thermal properties of two biochar-amended soils over a range of soil water contents. Two soils are used in the experiment: Hartsells sandy loam and Decatur silt loam.  These soils were analyzed for particle size distribution, particle density, and organic matter content.  The biochar used in this study is a hardwood biochar.  Two biochar particle sizes are used.  Biochar is mixed with the soils, resulting in soil-biochar mixtures containing 0%, 1%, and 2% biochar on a mass basis. Soil thermal properties are measured using a KD2 Pro thermal properties analyzer (Decagon Devices, Pullman, WA). Estimates of the soil thermal properties, C (volumetric heat capacity), α (thermal diffusivity), and λ (thermal conductivity), and their variation with soil water content and mass of biochar added will be reported for the two soils.