Tuesday, November 6, 2007 - 11:15 AM
181-7
Developing New Electrical Conductivity Technique for Measuring Soil Bulk Density.
Andrea Sz. Kishné, Soil & Crop Sciences, Texas A&M University, Texas AgriLife Research, College Station, TX 77843-2474, Cristine L.S. Morgan, Department of Soil & Crop Sciences, Texas A&M Univ., College Station, TX 77845-2474, and László B. Kish, Electrical and Computer Engineering, Texas A&M Univ., College Station, TX 77843-3128.
Measuring soil bulk density in situ requires destructive sampling, installing an access tube for nuclear measurement or using TDR, which is affected by salinity (ESP>9 dS m-1) even with coated electrodes. A new method, using vibration-induced conductivity fluctuation (VICOF) is proposed. It is hypothesized that this new method may be insensitive to salinity. This method is being experimented with in the laboratory, but might have field application in the future. To take a VICOF measurement, the AC electrical conductivity of soil is measured using a pair of blade-like electrodes while exposing the soil to periodic vibration. The normalized VICOF is expected to provide data independent from the vibration strength and to reduce the effect of soil salinity and water content. An experiment was conducted on natural and salinized fine sand (ESP=15 dS m-1) at two moisture conditions and four bulk densities. The blade-shaped electrode changed electrode-soil contact compared to cylindrical electrodes (used previously) and reduced measurement noise. Measurement of dry sand showed a negative correlation between the normalized conductivity fluctuation and soil bulk density. The wet natural and salinized soils performed very similarly, as hypothesized, but there was insensitivity to bulk density that was attributed to set-up conditions. Further results will be presented.