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A new digital electromechanical system for measurement of soil bulk density

Al-Shammary, Ahmed Abed Gatea, Kouzani, Abbas, Saeed, Thamir R., Rodrigo-Comino, Jesús
Computers and electronics in agriculture 2019 v.156 pp. 227-242
automation, bulk density, labor, soil density, soil depth, soil quality, soil texture
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.