Most upland sandy soils of the southeastern coastal plain have a compacted zone or hardpan which limits root penetration below the plowing depth, reducing yields, and making plants more susceptible to drought stress. There is a great amount of variability in depth and thickness of hardpan layers in this region. A real-time, sensor-based, site-specific tillage could achieve significant savings in tillage energy and increase crop yields. Replicated tests were conducted to evaluate the performance of the Clemson instrumented shank under actual field conditions. The instrumented shank was calibrated against cone penetrometer readings on three coastal plain soil types. The effects of soil moisture on shank performance was determined. There was a strong positive correlation between soil strength values measured with the penetrometer and the instrumented shank. It is possible to determine the depth and thickness of the hardpan layers with the instrumented shank either for real time control of subsoiling location and depth or for generating site-specific tillage maps.