Development and Field Evaluation of a Field-Ready Soil Compaction Profile Sensor for Real-Time Applications

Although the first prototype of a soil compaction profile sensor (SCPS) developed at the University of California Davis performed well in terms of sensing variation in soil compaction level with operating depth, it indicated a need for design improvements in three aspects - cost, size, and operational characteristics. The goal of this study was to design, fabricate, and test a field-ready device with enhanced capabilities to sense the differences in soil compaction along a profile down to a depth of 46 cm. The new design had close resemblance to commercially available subsoiler shanks. This new sensor used five custom-made load cells with their rated capacity adjusted to their location along the shank to achieve consistent sensitivity. Cutting elements of 63.5 mm in height were directly connected to these force transducers. The total thickness of the sensor was 28.6 mm. This sensor was tested in a Yolo silt loam field at different moisture contents. The results indicated that the new sensor had similar response characteristics as the older prototype since its output correlated with soil moisture content and density just like its predecessor. Likewise, its output also correlated with soil cone index values very well. This sensor was interfaced with a Differential Global Position System (DGPS) to geo-reference its output. Field evaluation was performed at the farm level in two fields with soils typical of the Midwest United States. Numerous cone penetrometer readings were obtained to compare with the output of the soil compaction sensor. Results also indicated that the improved SCPS can detect differences in the compaction state of the soil profile reasonably well. Moreover, sensor data was processed to generate tillage depth prescription maps to show the feasibility of site specific tillage.