Repeated geophysical measurements in dry and wet soil conditions to describe soil water content variability

Abstract

There is an increasing interest in the application of geophysical surveys to assess the soil water content (SWC) variation in both spatial and temporal scales. In this work, a geophysical survey was carried out at an experimental farm in dry and wet conditions. We determined the SWC data measured with the gravimetric method, apparent electrical conductivity by electromagnetic induction (EMI) and amplitude of Ground Penetrating Radar (GPR) data at different frequencies. Geophysical sensors are an efficient tool for soil mapping at high resolution; however; there is a need to improve the knowledge on their capabilities and limitations under field conditions, especially for GPR. The geophysical survey provides an example of the application of these techniques to evaluate the spatial variability of SWC in two different water conditions. The contribution of geophysical data in understanding the spatial variability of SWC was investigated applying both the traditional analysis and spatial techniques. The results indicated that the geophysical data captured the spatial variation of SWC in non-invasively way especially in dry condition. However, they also showed the complex interplay between factors controlling SWC and geophysical responses and the drawbacks of geophysical sensors under inhomogeneous water conditions. Our findings also highlighted that EMI survey provides the potential to map the SWC variability within a relatively short time. The results obtained in this research are important from the agronomical viewpoint, since they allow increasing efficiency of irrigation practices, which is important in times characterized by climate change.

Mapping an Agricultural Field Experiment by Electromagnetic Induction and Ground Penetrating Radar to Improve Soil Water Content Estimation

“…This result suggested that the variability of the moisture content did not significantly influence the variability of the ECa and, probably, the correlation could be the highest with other soil properties. Therefore, although previous studies refer to the influence of soil moisture on electrical conductivity [47][48][49], the findings of this research indicated limitations for the use of EMI sensors as an indicator of SWC and that one sensor alone cannot achieve a good estimation of soil spatial variation [41,42]. Since both the surface topography and the soil discontinuities play an important role in influencing spatial ECa variation [50], the radargram analysis and interpretation might help to identify soil discontinuities and their depths.…”

“…However, since the spatial patterns of SWC could have been influenced by the variations in soil depth and soil/bedrock interface [40], the combination of different sensors and integrating their data could discriminate whether or not agronomical factors (hydraulic arrangement, organic amendment application, etc.) can modify SWC distribution [41], and could also provide its more accurate…”

Application of the Ground Penetrating Radar (GPR) and Electromagnetic (EM34-3) Geophysical Tools and Sedimentology for the Evaluation of the Subsurface of Sites Earmarked for Aquaculture Ponds in the Amazon Region of Northern Brazil

“…The maximum depth of these ponds is approximately 1.6 m (Figure Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI) can be tremely valuable for the collection of spatial data that correlate with the soil types Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI) can be extremely valuable for the collection of spatial data that correlate with the soil types and Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI) can be extremely valuable for the collection of spatial data that correlate with the soil types and hydrological properties of a terrain (e.g., [88][89][90][91][92]). The geophysical survey techniques employed in the present study have also been used to successfully investigate the physical properties of the soil and subsoil in research in scientific fields such as agronomy, archeology, hydrology, and wetland ecology (e.g., [23,37,88,[93][94][95][96][97][98][99][100][101][102][103][104][105][106]). References [22,107] predicted that the integration of geophysical tools (e.g., Electrical Resistivity Tomography (ERT), EMI, and GPR) with remote sensing will contribute to the successful development of precision agriculture.…”