A new digital electromechanical system for measurement of soil bulk density

This research describes the automation of the widely used volumetric cylinder (VC) technique to measure bulk
density. The VC technique suffers from several major drawbacks. In particular, it is difficult and time-consuming
to use. Furthermore, errors are produced when sampling different soil depths under a range of field conditions.
This research introduces the design, implementation, and testing of a digital electromechanical system (DES) for
measuring and recording of the dry (ρb) and wet (ρn) bulk density of soil at three soil depths, remotely. The DES
design is a novel and own design. The results of field testing showed that the DES can measure the bulk density of
soil at different depths in considerably less time and labour, showing a better accuracy than the existing VC
techniques for specific soil textures. The accuracy of the DES-based estimates soil bulk density influenced by
different soil textures and soil depths. The first major finding is that for a 10 cm soil depth, both the DES and VC
methods produced lower ρb and ρn values for soil as compared to other soil depths under various soil conditions.
The second major finding is that there is a positive correlation between the DES and the VC methods for the
measurement of both ρb and ρn of soil, with a coefficient of determination (R2
) of 0.87 and 0.73, respectively. The
coefficient of variation (CV) of dry ρb and wet ρn of soil with the DES method was 6% and 6.3%, respectively,
while for the VC method, the CV was 6.3% for ρb and 6.1% for ρn. Furthermore, there was a linear relationship
between the DES and the VC methods under different moisture conditions. We conclude that soil bulk density is
generally most accurately and precisely determined by the DES technology