Field evaluation of the improved version of the UCDavis compaction profile sensor (UCD-CPS)

Our experience with the development of the first prototype of the UC Davis soil compaction profile sensor allowed us to define design parameters for improvements in three areas: cost, size, and operational characteristics. The goal was to design, fabricate, and test a field-ready, cost-effective device with enhanced capabilities to sense the differences in soil compaction along a profile up to a depth of 46 cm. The new design has 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. Field tests were performed on a Yolo loam soil at different moisture contents. The results of this phase indicated that the new sensor had similar response characteristics as the older prototype. The output of this sensor correlated with soil moisture content and density just like in the case of its predecessor. Moreover, 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 a variety of soils typical of the US Mid-west. Numerous Cone Penetrometer readings were obtained to compare with the output of the soil compaction sensor. Except in stony soils, the sensor was able to stand the field conditions during extensive fieldwork with significant reliability. Results indicate that the improved UCD-CPS can detect differences in the compaction state of the soil profile reasonably well.