Abstract: An apparatus and method are provided for continuously measuring the soil strength on-the-fly and at different depths. The apparatus includes a downwardly extending probe having an impedance sensor mounted on a leading edge thereof so as to be impacted by the soil as the probe is moved in a horizontal direction therethrough. A reciprocating drive is also provided which is effective for simultaneously oscillating the probe in an up and down movement while it is passing horizontally through the soil. The mechanical impedance exerted upon the sensor is then measured as the probe is passed both horizontally and up and down through said soil, thereby providing a continuous depth-variable profile of the soil strength over a large area.