Resistivity characteristics of organic soils under different water content and temperature conditions

This dataset provides raw AC impedance measurements and derived electrical resistivity of an organic-matter-amended clay-rich soil under controlled temperature (including frozen states), water content, and organic-matter (OM) content. We hypothesize that soil resistivity is governed by the coupled effects of temperature/freezing, moisture level, and OM amendment, while compaction-induced porosity variability and exogenous water chemistry are minimized so that observed electrical differences primarily reflect the designed factors. A composite bulk soil sample was collected from 10 random points (20–50 cm depth) within a relatively uniform field site in Lintong District, Xi’an, China, homogenized in the laboratory, and characterized by basic physical properties, particle-size distribution, and qualitative XRD mineralogy (illite/kaolinite with quartz). Sycamore residues were dried, ground (<2 mm), and mixed into the soil at OM contents of 1%, 3%, 4%, and 5%, with target gravimetric water contents of 12%, 14%, 16%, and 18%. Specimens were compacted in a fixed-volume ring cutter (D = 61.8 mm, L = 20 mm), and representative mass checks confirm a narrow dry-density range (≈1.669–1.688 g/cm³), indicating consistent compaction among groups.
A full-factorial design of 7 temperatures (10, 0, −3, −5, −10, −15, −20 °C) × 4 water contents × 4 OM contents was implemented (112 conditions), with two parallel compacted specimens tested per condition (n = 2; 224 specimens total). After isothermal equilibration (12 h at each target temperature), complex impedance was measured using a Tonghui TH2816A LCR meter at 1 kHz and 1.0 V with a two-plate electrode configuration (polished copper), OPEN/SHORT compensation, and controlled normal load. The raw outputs include the real and imaginary impedance components (R = Re(Z), X = Im(Z), in Ω) and the phase angle (φ, in degrees). Resistivity is calculated using the fixed specimen geometry as ρ = (S/L)·R = 0.15·R (Ω·m). The phase angles are consistently small and negative under the 1 kHz protocol, indicating that the response is predominantly resistive with limited reactive contribution, and contact/polarization effects are treated as part of measurement uncertainty. To aid interpretation of ionic-strength effects, electrical conductivity (EC) of 1:5 soil–water extracts was measured at 15 °C for representative OM levels (1% and 5%) with short-term repeatability checks (48 h), providing a comparable indicator of relative pore-water salinity among mixtures.
The dataset can be used to quantify resistivity–temperature relationships across unfrozen and frozen conditions, evaluate the effects of moisture and OM amendment (and their interactions), and support empirical modeling or calibration/validation studies.