Analysis of Different Electric Current Frequencies in Soil Apparent Conductivity

Purpose The electrical resistivity method is commonly used to identify areas with similar soil characteristics by measuring the soil’s apparent electrical conductivity (EC a ). However, the ideal frequency range to be used and the influence of the signal frequency on EC a values obtained by sensors is still uncertain. This study aimed to (1) evaluate the effect of electric current frequency on EC a values and (2) evaluate the correlation between EC a values obtained from different frequencies and soil attributes of agronomic interest, such as soil water content and pH. EC a determinations were obtained in four experimental areas using six different frequencies of electric current (1, 5, 10, 20, 30, and 40 Hz). Methods The influence of the electric current signal frequency on the value obtained by the sensor was analyzed by linear regressions in all experimental areas, followed by the F- test ( α = 0.05). Pearson’s correlations ( α = 0.05) were calculated to quantify the relationships between EC a and soil physical and chemical attributes, for each frequency of the electric current signal of the sensor. Results Statistical analyses indicated that the electric current frequency does not significantly affect the measured conductivity value. According to the chi-square test ( p ≤ 0.05), the number of significant correlations between EC a and soil physical and chemical attributes was homogeneous for all frequencies. The F -test indicated that the frequency of the electric current had no significant effect on EC a in 90% of the experimental points. Conclusion It was shown that all frequencies in the range of 1 to 40 Hz can be used to correlate EC a values with chemical and physical soil attributes, such as soil water content ( r = 0.73, p < 0.05) and exchangeable calcium content ( r = 0.66, p < 0.05).