Applications of GPR in Detecting Soil Heterogeneities and Modeling Controlled Drainage Systems.

Ground Penetrating Radar (GPR) technology appears to be a good alternative to conventional methods for mapping soil properties and identify spatial variability at the field and farm scales. GPR technique is a non-invasive geophysical method using high-resolution electromagnetic waves to probe the soil profile. Knowing soil profile heterogeneities is crucial for water management in precision agriculture, moreover when a subirrigation and a well-designed and fully functional drainage systems are the objectives. The causes of poor drainage are numerous ranging from poor design to discontinuities in the soil profile and spatial heterogeneities of soil hydraulic properties. The objective of this work was to develop a method to characterize spatial heterogeneity of soil hydraulic properties at the field scale using GPR measurements. To achieve this, an ongoing experiment allows the characterization of the subsurface topography and stratification of cranberry fields with a GPR. Two antennas (270 and 400 MHz) were used on transects perpendicular to the drains. Results of GPR data processing showed that groundwater, soil layers and drains can be distinguished in the soil profile and a difference in drainage performance has been noted between fields. The 3D modeling of GPR profiles allowed the identification of the highest reflective areas and the characterization of within field spatial heterogeneities, suggesting bad drainage zones. GPR imagery maps were compared to saturated hydraulic conductivity maps and other soil properties measured in the field. Preliminary results indicate a good agreement between GPR images and soil properties maps.