Electrical Resistivity Changes Due to Fertilization in Agricultural Soil

Excessive use of fertilizers in agriculture can cause soil contamination. The worst impact of this is making the land unproductive for farming. One of the things that can be done to prevent soil contamination is to identify the content of the fertilizer solution in the soil by utilizing the electrical properties of the soil. In this study, the soil electrical resistivity changes affected by fertilizer solution content were analyzed by measuring soil samples and electrical resistivity tomography (ERT). Twelve soil samples from agricultural land were prepared for laboratory-scale resistivity measurements. The samples were injected with four fluid solutions, i.e., compost, NPK, urea, and rainwater, with various concentrations and degrees of saturation. The results of laboratory investigations form the basis for interpreting ERT data in the field. Then ERT was carried out in the agricultural area before and after the fertilization process to analyze changes in the electrical resistivity of the soil using the dipole-dipole configuration. The results show that the electrical resistivity of the soil is very dependent on the level, concentration, and type of fertilizer. The correlation between soil electrical resistivity and fertilizer content can be approximated by the Archie equation with R2 = 0.9. In addition, empirical relationships between soil electrical resistivity and the physical properties of the fertilizer solution, i.e., resistivity, total dissolved solids (TDS), salinity, and pH, were also obtained. The study findings should make an important contribution to determining fertilizer levels and the sustainability of the agricultural environment.