Abstract: Accuracy of soil resistivity measuring result in the laboratory will be influenced by electrodes arrangement, types of test signal, etc. Five types of soils with different textures are selected to investigate the influencing factors of soil resistivity measurement. A comparison of resistivity measuring results between four-electrode method and two-electrode method is made firstly; and the influence of potential electrode penetrations in four-electrode method is also studied. A comparison between the resistivity measuring results with DC and AC voltage test signal is made. Moreover, influence of the current density and AC signal frequency on soil resistivity measuring results has also been investigated here. The results have shown that, measuring results by two-electrode method contain the contact resistance between electrodes and the soil, which will increase rapidly when the water content of soils decreases. The soil resistivity test can be performed with little penetration, or little disturbance to the tested soils by the four-electrode method. Alternating current test signal should be used to prevent polarization effect of DC voltage. Due to the fact that thermal capacity of the test soil is limited, current densities should be kept less than 1 mA•cm-2 to test soils with electrical resistivity less than 200 Ω•m. Soil resistivity has been found to be decreased as test signal frequency increases.

Key words: soil resistivity, two-electrode method, four-electrode method, contact resistance, polarization effect