Assessment of the Combined Effect of Temperature and Salinity on the Outputs of Soil Dielectric Sensors in Coconut Fiber

Sebastián Bañón, Jesús Ochoa, Daniel Bañón, María Fernanda Ortuño and María Jesús Sánchez-Blanco
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Sebastián Bañón: Department of Agricultural Engineering, UPCT—Technical University of Cartagena, 30203 Cartagena, Spain
Jesús Ochoa: Department of Agricultural Engineering, UPCT—Technical University of Cartagena, 30203 Cartagena, Spain
Daniel Bañón: Department of Irrigation, CEBAS-CSIC—Center for Edaphology and Applied Biology of Segura, 30100 Murcia, Spain
María Fernanda Ortuño: Department of Irrigation, CEBAS-CSIC—Center for Edaphology and Applied Biology of Segura, 30100 Murcia, Spain
María Jesús Sánchez-Blanco: Department of Irrigation, CEBAS-CSIC—Center for Edaphology and Applied Biology of Segura, 30100 Murcia, Spain

Sustainability, 2020, vol. 12, issue 16, 1-14

Abstract: Dielectric sensors are useful instruments for measuring soil moisture and salinity. The soil moisture is determined by measuring the dielectric permittivity, while bulk electrical conductivity (EC) is measured directly. However, permittivity and bulk EC can be altered by many variables such as measurement frequency, soil texture, salinity, or temperature. Soil temperature variation is a crucial factor as there is much evidence showing that global warming is taking place. This work aims to assess how variations in the temperature and salinity of coconut fiber affect the output of EC5 (voltage) and GS3 (permittivity and bulk EC) Decagon sensors. The results showed that the effect of temperature and salinity on the output of the sensors can lead to substantial errors in moisture estimations. At low salinity values, permittivity readings decreased as temperature increased, while voltage readings were not affected, regardless of substrate moisture. The GS3 sensor underestimated the bulk EC when it is measured below 25 °C. The temperature dependence of the voltage of EC5 was not significant up to 10 dS m −1 , and the permittivity of the GS3 was more affected by the interaction between temperature and salinity. The effect that salinity has on the permittivity of the GS3 sensor can be reduced if a permittivity–moisture calibration is performed with saline solutions, while the effect resulting from the interaction between temperature and salinity can be minimized using a regression model that considers such an interaction.

Keywords: soil moisture; probe; salinity; volumetric water content; temperature (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
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