Measuring Soil Bulk Density by Using Vibration-induced Conductivity Fluctuation A. Sz. Kishné, C. L.S. Morgan Dept. of Soil and Crop Sciences, Texas A&M University, College Station, TX, USA L. B. Kish Dept. of Electrical and Computer Engineering, Texas A&M University, College Station, TX, USA Objectives Materials and Methods Results References 1.Introduce a new, non-destructive method for measuring soil bulk density by exposing soils to a periodic vibration and measuring the vibration-induced conductivity fluctuation (VICOF) 2.Test the measurement principles on packed soil samples 3.Test the effect of salinity and moisture on VICOF at current measurement setup  Kish,L.B., C.L.S. Morgan and A.Sz. Kishné (2006). Vibration-induced Conductivity Fluctuation Testing of Soils. Fluctuations and Noise Letters. Submitted  Texas A&M University patent disclosure (November 2005)  Appreciation is expressed to Dr. K. McInnes and Dr. T. Hallmark (TAMU) for their valuable suggestions for compacting and salinizing the soil samples, respectively.  The research was supported by Texas Agricultural Experiment Station. Resistance fluctuation (dR s )Normalized resistance fluctuation (dR s /R s ) Measurement circuitry: Ground To the lock-in amplifier Soil resistance (modulated by f 2 ) R1R1 U 1 [f 1 =1kHz] RsRs U 2,1 [f 1 ] U 2,2 [f 1 +2f 2 and f 1 -2f 2 ] AC Voltage generator Driving resistor Vibration by f 2 ~ Justification 1. Soils Texture Class Clay Fine sand Particle Size Distribution ClaySiltSand % Elec.Cond. (sat.paste) dS m Discussion and Conclusions  A curvilinear, inverse relationship exists between normalized vibration-induced resistance fluctuation and soil bulk density that is specific for soil texture.  Soil moisture and salinity effects this relationship at 60 Hz vibration frequency, but these effects may be eliminated by taking measurements at multiple frequencies.  Instrument noise increases with increasing bulk density. Error ratio and soil-electrode contact is expected to improve with the use of a blade-shaped compared to the current needle-shaped electrode.  According to preliminary result, salinity (2 dS m -1 ) has a minimal effect on the measurement Acknowledgements Measurement Errors (Normalized to Signal) SD / Averaged dR s /R s ClayFine Sand Comp1Comp2Comp3Comp4Comp1Comp2Comp3 Comp4 DWDWDWDWDWDWDWDW Instrument noise Within sample Within treatment Quantification of soil bulk density under field conditions is time consuming and difficult. A novel method for quantifying soil bulk density in the field involves using recent advances in fluctuation and noise research. Theoretically this method can be made independent of soil salinity and moisture. Possible application of this method is explored. Principles 3. Experimental setup for the electrical conductivity measurements 4. Lock-in amplifier 3. Periodic vibrator, 60 Hz 2. Antivibration table 1. Electrode (0.3cm diam. & 7.1 cm length) 5. Software for averaging signal over time average signal Time period: 30 sec: U 1 & U 2,1 90 sec: U 2,2,0 & U 2,2,vibr 5 2. Soil sample treatments 1 kg 3 kg Weights compacting the soils by layers Wet Soil: J kg -1 (D) and -100 J kg -1 (W) (clay: cm 3 cm -3, sand: cm 3 cm -3 ) Compacted Soil: used a 1 kg or 3 kg weight Comp 1 Comp 2 Comp 3 Comp 4 Salinizied Fine Sand: 2 dS m -1 EC in saturated paste Clay (g cm -3 ) Fine Sand (g cm -3 ) Normalized Resistance Fluctuation vs. Soil Bulk Density dR s /R s Bulk Density (g cm -3 ) Normalized Resistance Fluctuation vs. Soil Bulk Density Clay, 1000 J kg -1 Clay, 100 J kg -1 Fine sand, 1000 J kg -1 Salinized sand, 100 J kg -1 * Electrical contact problem (left out of fitting the model) * * * * * * Fine sand, 100 J kg dR s /R s Bulk Density (g cm -3 ) * * Clay, 1000 J kg -1 Clay, 100 J kg -1 Fine sand, 1000 J kg -1 Salinized sand, 100 J kg -1 * Electrical contact problem (left out of fitting the model) * * Fine sand, 100 J kg -1 * *