Evaluation of the Clemson instrumented subsoiler shank in coastal plain soils

Most sandy soils in coastal plains of the southeastern USA have a compacted zone or hardpan which limits root penetration below the plowing depth, reducing yields, and predisposing plants to drought stress. The hardpan layer exhibits a great amount of variability in depth and thickness in this region. Real-time, sensor-based, site-specific tillage could achieve significant savings in energy requirements for subsoiling and increase crop yields. Replicated tests were conducted to evaluate the performance of the Clemson instrumented subsoiler shank under actual field conditions. The instrumented subsoiler shank was calibrated against cone penetrometer readings on three coastal plain soil types. A strong positive correlation between soil strength values measured with the penetrometer and the instrumented subsoiler shank was observed (R²=0.89-0.97). On average, the shank index values (measured horizontally) were about 50% less than the corresponding cone index values (measured vertically). The effect of soil moisture content on shank-penetrometer correlation was not significant (α=0.05). It is possible to determine the depth and thickness of the hardpan layers with the instrumented subsoiler shank either for real time control of subsoiling location and depth or for generating site-specific tillage maps.