Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe

Abstract

Capacitance and resistivity sensors can be used to continuously monitor soil volumetric water content (θ) and pore-water electrical conductivity (ECp) with non-destructive methods. However, dielectric readings of capacitance sensors operating at low frequencies are normally biased by high soil electrical conductivity. A procedure to calibrate capacitance-resistance probes in saline conditions was implemented in contrasting soils. A low-cost capacitance-resistance probe (ECH2O-5TE, 70 MHz, Decagon Devices, Pullman, WA, USA) was used in five soils at four water contents (i.e., from dry conditions to saturation) and four salinity levels of the wetting solution (0, 5, 10, and 15 dS·m−1). θ was accurately predicted as a function of the dielectric constant, apparent electrical conductivity (ECa), texture and organic carbon content, even in high salinity conditions. Four models to estimate pore-water electrical conductivity were tested and a set of empirical predicting functions were identified to estimate the model parameters based on easily available soil properties (e.g., texture, soil organic matter). The four models were reformulated to estimate ECp as a function of ECa, dielectric readings, and soil characteristics, improving their performances with respect to the original model formulation. Low-cost capacitance-resistance probes, if properly calibrated, can be effectively used to monitor water and solute dynamics in saline soils.

Laboratory Performance of Five Selected Soil Moisture Sensors Applying Factory and Own Calibration Equations for Two Soil Media of Different Bulk Density and Salinity Levels

“…They also stated that the older type ECH 2 O EC-20 was more sensitive to bulk electrical conductivity than ECH 2 O EC-5. Scudiero et al [53] suggested using a newer version of ECH 2 O TE, ECH 2 O 5TE, which works at a frequency of 70 MHz for continuous monitoring of soil moisture content and solute dynamics in saline soils. …”

Experimental study of the complex resistivity and dielectric constant of chrome-contaminated soil

“…The coaxial terminal open circuit reflection method was used to determine the complex dielectric constant within a frequency range of 10 MHz to 1 GHz (Sakellis et al, 2014;Scudiero et al, 2012). Fig.…”

Recent developments in nanotechnology transforming the agricultural sector: a transition replete with opportunities

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