Evaluation and recommendations for the use of dynamic penetrometers

Abstract

Dynamic penetrometers are largely used for studies of soil compaction caused by agricultural practices. In this paper, some critical factors affecting precision, operation time, and ease of use of dynamic penetrometers were evaluated. An alternative procedure recording the number of strikes for pre-defined layers (NL) was proposed and compared to the conventional procedure that records depths per strike (Dn). Mass and falling height variability of commercial penetrometers were assessed and the effects on the penetration resistance (PR) equations were evaluated. Comparisons between dynamic and static penetrometers were performed for soils of different textures and a device to extract dynamic penetrometers from very compacted soils was proposed. The alternative procedure-NL presented no statistical difference to the conventional procedure-Dn, shorter acquisition times and simple data post-processing, which was recommended for routine analysis. Mass and falling height variability of 22 Stolf/IAA penetrometers significantly impacted the equations to calculate PR, with variations from −5 to +10% compared to the standard equation. Thus, users should utilize their own equations to transform raw data in PR. The dynamic penetrometer performance was significantly affected by soil texture as compared to the static penetrometer. The puller device was effective for extracting the dynamic penetrometers from soils with PR higher than 5 MPa.