Conductivity and relative permittivity measurements in different soil types and moisture levels

Relative permittivity and electric conductivity measurements were taken from soil samples at different moisture levels. Sand, sandy loam, and silty loam soil samples were dried and moisture was then elevated gradually by 5% intervals up to 35% and measurements were taken at each moisture level (0, 5, 10, 15, 20,... 35%). Moisture was increased on a volumetric soil water basis (cm³ of water /cm³ of soil) in a 588cm³ soil sample. This experiment was replicated 6 times. The sensor types used to capture measurements were SMT100 (Truebner, Germany) for relative permittivity and a TZT module (China) with an inverted signal (1/ρ) for conductivity. Relative permittivity measurements were recorded using the Modbus V3 software, and using an Arduino uno board (ATmega328P microcontroller) which inverted the raw resistance signal (1/ρ) to a unitless conductivity signal.All soil samples had low salinity levels (~0.1 dS/m) and slightly alkaline pH (8.4). Water added to control moisture levels has low salinity (TDS: 370 ppm) and slightly alkaline (pH: 7.9) characteristics.