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Laboratory calibration and field validation of soil water content and salinity measurements using the 5TE sensor

Zemni, Nessrine LU ; Bouksila, Fethi LU ; Persson, Magnus LU ; Slama, Fairouz ; Berndtsson, Ronny LU and Bouhlila, Rachida (2019) In Sensors (Switzerland) 19(23).
Abstract

Capacitance sensors are widely used in agriculture for irrigation and soil management purposes. However, their use under saline conditions is a major challenge, especially for sensors operating with low frequency. Their dielectric readings are often biased by high soil electrical conductivity. New calculation approaches for soil water content (θ) and pore water electrical conductivity (ECp), in which apparent soil electrical conductivity (ECa) is included, have been suggested in recent research. However, these methods have neither been tested with low-cost capacitance probes such as the 5TE (70 MHz, Decagon Devices, Pullman, WA, USA) nor for field conditions. Thus, it is important to determine the performance of these approaches and to... (More)

Capacitance sensors are widely used in agriculture for irrigation and soil management purposes. However, their use under saline conditions is a major challenge, especially for sensors operating with low frequency. Their dielectric readings are often biased by high soil electrical conductivity. New calculation approaches for soil water content (θ) and pore water electrical conductivity (ECp), in which apparent soil electrical conductivity (ECa) is included, have been suggested in recent research. However, these methods have neither been tested with low-cost capacitance probes such as the 5TE (70 MHz, Decagon Devices, Pullman, WA, USA) nor for field conditions. Thus, it is important to determine the performance of these approaches and to test the application range using the 5TE sensor for irrigated soils. For this purpose, sandy soil was collected from the Jemna oasis in southern Tunisia and four 5TE sensors were installed in the field at four soil depths. Measurements of apparent dielectric permittivity (Ka), ECa, and soil temperature were taken under different electrical conductivity of soil moisture solutions. Results show that, under field conditions, 5TE accuracy for θ estimation increased when considering the ECa effect. Field calibrated models gave better θ estimation (root mean square error (RMSE) = 0.03 m3 m−3) as compared to laboratory experiments (RMSE = 0.06 m3 m−3). For ECp prediction, two corrections of the Hilhorst model were investigated. The first approach, which considers the ECa effect on K’ reading, failed to improve the Hilhorst model for ECp > 3 dS m−1 for both laboratory and field conditions. However, the second approach, which considers the effect of ECa on the soil parameter K0, increased the performance of the Hilhorst model and gave accurate measurements of ECp using the 5TE sensor for irrigated soil.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
FDR sensor, Real time monitoring, Sensor calibration and validation, Soil pore water electrical conductivity, Soil salinity, Soil water content
in
Sensors (Switzerland)
volume
19
issue
23
article number
5272
publisher
MDPI AG
external identifiers
  • scopus:85076115125
  • pmid:31795495
ISSN
1424-8220
DOI
10.3390/s19235272
language
English
LU publication?
yes
id
5a12db28-4625-4ab9-bc93-6855122e79d9
date added to LUP
2020-01-03 16:20:36
date last changed
2020-01-04 03:00:03
@article{5a12db28-4625-4ab9-bc93-6855122e79d9,
  abstract     = {<p>Capacitance sensors are widely used in agriculture for irrigation and soil management purposes. However, their use under saline conditions is a major challenge, especially for sensors operating with low frequency. Their dielectric readings are often biased by high soil electrical conductivity. New calculation approaches for soil water content (θ) and pore water electrical conductivity (ECp), in which apparent soil electrical conductivity (ECa) is included, have been suggested in recent research. However, these methods have neither been tested with low-cost capacitance probes such as the 5TE (70 MHz, Decagon Devices, Pullman, WA, USA) nor for field conditions. Thus, it is important to determine the performance of these approaches and to test the application range using the 5TE sensor for irrigated soils. For this purpose, sandy soil was collected from the Jemna oasis in southern Tunisia and four 5TE sensors were installed in the field at four soil depths. Measurements of apparent dielectric permittivity (Ka), ECa, and soil temperature were taken under different electrical conductivity of soil moisture solutions. Results show that, under field conditions, 5TE accuracy for θ estimation increased when considering the ECa effect. Field calibrated models gave better θ estimation (root mean square error (RMSE) = 0.03 m<sup>3</sup> m<sup>−3</sup>) as compared to laboratory experiments (RMSE = 0.06 m<sup>3</sup> m<sup>−3</sup>). For ECp prediction, two corrections of the Hilhorst model were investigated. The first approach, which considers the ECa effect on K’ reading, failed to improve the Hilhorst model for ECp &gt; 3 dS m<sup>−1</sup> for both laboratory and field conditions. However, the second approach, which considers the effect of ECa on the soil parameter K0, increased the performance of the Hilhorst model and gave accurate measurements of ECp using the 5TE sensor for irrigated soil.</p>},
  author       = {Zemni, Nessrine and Bouksila, Fethi and Persson, Magnus and Slama, Fairouz and Berndtsson, Ronny and Bouhlila, Rachida},
  issn         = {1424-8220},
  language     = {eng},
  month        = {11},
  number       = {23},
  publisher    = {MDPI AG},
  series       = {Sensors (Switzerland)},
  title        = {Laboratory calibration and field validation of soil water content and salinity measurements using the 5TE sensor},
  url          = {http://dx.doi.org/10.3390/s19235272},
  doi          = {10.3390/s19235272},
  volume       = {19},
  year         = {2019},
}