Heat Pulse Probe-Based Smart Soil Moisture Detection System

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 mineral composition. Primarily, a novel model for the heat strength of the probe of HPP is proposed and examined. It results in
${R}^{{2}} =0.9809$
, adjusted
${R}^{{2}} =0.9721$
, and root mean square error (RMSE) of 5.73 W/m for experimentally measured values versus 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 to 0.306
$\text{m}^{{3}}/\text{m}^{{3}}$
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 previous studies and linked with futuristic applications.
${R}^{{2}} =0.9763$
, adjusted
${R}^{{2}} =0.9527$
, and RMSE of 0.032
$\text{m}^{{3}}/\text{m}^{{3}}$
are obtained for soil moisture measured experimentally versus values obtained using the proposed model.