Effects of machinery trafficking in an agricultural soil assessed by Electrical Resistivity Tomography (ERT)

Soil compaction is a serious problem, which is aggravated due to its difficulty to locate and reverse. Electrical resistivity tomography (ERT) is a non-invasive geophysical method that can be used to identify compacted areas, soil horizon thickness and assess soil physical properties. This study assesses the relationship between ERT and soil compaction. Data were collected on a 4-m transect in a fallow plot located at Braganca (Portugal). Measurements were performed before and after tillage and tractor passage. Soil samples at different depths (0-0.05, 0.05-0.1 and 0.1-0.2 m depth) were taken to determine: soil bulk density, porosity, saturated hydraulic conductivity and soil water content. The effect of tillage and tractor passage was more significant on the first 0.05 m depth. In the wheel track areas, ERT suffered a reduction of about 40%, saturated hydraulic conductivity decreased by 70% and bulk density increased by 24%. These results proved that ERT can be a useful tool for assessing soil compaction