Abstract
The existing soil moisture sensing mechanism of the heat pulse probe (HPP) assumes the ideal condition of the soil while overlooking the Physics of the device and the composition of the soil and its properties. In the present study, we propose modifications to the soil moisture sensing model of HPP by considering its physical parameters and their appropriate association with the thermal properties of soil and its minerals composition. Primarily, a novel model for the heat strength of the probe of HPP is proposed and examined. It results in R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.9809, adjusted R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.9721, and root mean square error (RMSE) of 5.73 W/m for experimentally measured values vs. obtained values of heat strength using the proposed model. Subsequently, a soil composition-based model is developed resulting in a 19-25% change in the bulk volumetric heat capacity of the soil. A final model of soil moisture estimation is developed by combining the heat strength of the probe of HPP, and the bulk volumetric heat capacity and porosity of the soil. The proposed model suggests improved results in soil moisture measurement in the range of -0.004 – 0.306 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> which can be useful for different applications and several types of soil. Moreover, the model predicted values of soil moisture are validated with experimental values in past studies and linked with futuristic applications. R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.9763, adjusted R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.9527, and RMSE of 0.032 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> are obtained for soil moisture measured experimentally vs. values obtained using the proposed model.
Published Version
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