  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.
