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Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe
Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE), University of Padua, Viale dell'Università, 16, 35020 Legnaro, Italy
Department of Civil, Environmental and Architectural Engineering (ICEA), University of Padua, Via Trieste, 63, 35131 Padova, Italy
* Author to whom correspondence should be addressed.
Received: 12 November 2012; in revised form: 13 December 2012 / Accepted: 14 December 2012 / Published: 18 December 2012
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.
Keywords: capacitance-resistance probe; salinity; water content; pore-water electrical conductivity; probe calibration
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MDPI and ACS Style
Scudiero, E.; Berti, A.; Teatini, P.; Morari, F. Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe. Sensors 2012, 12, 17588-17607.
Scudiero E, Berti A, Teatini P, Morari F. Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe. Sensors. 2012; 12(12):17588-17607.
Scudiero, Elia; Berti, Antonio; Teatini, Pietro; Morari, Francesco. 2012. "Simultaneous Monitoring of Soil Water Content and Salinity with a Low-Cost Capacitance-Resistance Probe." Sensors 12, no. 12: 17588-17607.