Soil bulk density affects water storage, water and nutrient movement, and plant root activity in the soil profile. Its
measurement is difficult in field conditions. Vibration-induced conductivity fluctuation was investigated to quantify
soil bulk density with possible field applications in the future. The AC electrical conductivity of soil was measured
using a pair of blade-like electrodes while exposing the soil to periodic vibration. The blades were positioned
longitudinally and transversally to the direction of the induced vibration to enable the calculation of a normalized index.
The normalized index was expected to provide data independent from the vibration strength and to reduce the effect of
soil salinity and water content. The experiment was conducted on natural and salinized fine sand at two moisture
conditions and four bulk densities. The blade-shaped electrodes improved electrode-soil contact compared to
cylindrical electrodes, and thereby, reduced measurement noise. Simulations on a simplified resistor lattice indicate that
the transversal effect increases as soil bulk density decreases. Measurement of dry sand showed a negative correlation
between the normalized conductivity fluctuation and soil bulk density for both longitudinal and transversal settings. The
decrease in the transversal signal was smaller than expected. The wet natural and salinized soils performed very
similarly as hypothesized, but their normalized VICOF response was not significant to bulk density changes. This lack
of sensitivity might be attributed to the heavy electrodes and/or the specific vibration method used. The effects of
electrode material, vibration method and soil properties on the experiment need further study.
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