Spatial variability of soil thermal properties and their relationships with physical properties at field scale

Characterizing the spatial variability of soil thermal properties and quantifying their relationships with commonly measured soil physical properties is important for successful implementation of precision agriculture practices. However, such information at field scale is scarce. This study aimed to characterize the spatial variability of soil thermal properties and to quantify their spatial relationships with soil physical properties at a field scale. Measurements of soil water content (SWC) and thermal properties were carried out at 80 locations using a time domain reflectometry (TDR) probe and a heat pulse probe (Decagon KD2 Pro), respectively in a cultivated cornfield in southwestern QC, Canada. Soil texture and total organic carbon (TOC) at those locations were also determined in the laboratory. Both coefficient of variation (CV%) and variogram range showed a weak to moderate variability and spatial dependency for the soil properties which was attributed to the homogeneity of the soil, crop, and land management practices. Results of principle component analysis (PCA) indicated that the soil thermal properties and soil water content (SWC) had strong correlations with principle component 2 (PC2). The variogram ranges indicated that the soil thermal properties varied on a similar spatial scale as the SWC in the field. Cross variograms indicated strong spatial correlations between SWC and thermal properties, particularly thermal conductivity (k) and thermal diffusivity (D). Overall, results of this study showed that the SWC had a stronger influence on the spatial variability of soil thermal properties than the other properties such as TOC and soil texture at the field scale. Therefore, the results of this study could be useful for accurate modeling of the soil thermal regimes and mass-energy exchange processes at the field scale as well as developing successful agricultural management strategies such as precision irrigation. Future studies should explore the relation. ships between the thermal properties and other soil properties such as bulk density under various cropping systems.