Xicai Pan
On the laboratory calibration of dielectric permittivity models for agricultural soils: Effect of systematic porosity variation
Pan, Xicai; Han, Yudi; Chun, Kwok Pan; Zhang, Jiabao; Ma, Donghao; Gao, Hongkai
Authors
Yudi Han
Dr Kwok Chun Kwok.Chun@uwe.ac.uk
Lecturer in Environmental Managment
Jiabao Zhang
Donghao Ma
Hongkai Gao
Abstract
Dielectric techniques are fundamental methods for measuring soil water content, and they commonly rely on the conventional laboratory calibration of the dielectric permittivity models between a dielectric constant and water content. As a non-negligible factor, porosity has been constructed differently in some models as a calibration constant, but the systematic porosity variations during the laboratory model calibration and field applications are not yet well addressed. Based on time-domain reflectometer laboratory calibration experiments, this study investigated this issue using three preestablished dielectric permittivity models: the Purdue calibration equation (American Society for Testing and Materials model [ASTM]), the complex refractive index model (CRIM), and a piecewise CRIM model (CRIMP). Results demonstrate that a generalized porosity constant used in the calibration would bring in additional structural bias compared with the calibration using variable porosities, and its magnitude varies with the model structure. The deviation of the generalized porosity constant can further amplify the structural bias of ASTM and CRIM for soils with low clay content, but it is insensitive for the soils with high clay content due to the overwhelming role of model structure error. Only the model CRIMP with a “perfect” model structure can effectively cope with the systematic porosity variation and keep a stable built-in capability for estimating calibration constants from readily available soil data. These findings highlight ignoring porosity variation should not be taken for granted for calibrating and applying the preestablished models.
Citation
Pan, X., Han, Y., Chun, K. P., Zhang, J., Ma, D., & Gao, H. (2021). On the laboratory calibration of dielectric permittivity models for agricultural soils: Effect of systematic porosity variation. Vadose Zone Journal, 20(1), Article e20096. https://doi.org/10.1002/vzj2.20096
Journal Article Type | Article |
---|---|
Acceptance Date | Sep 15, 2020 |
Online Publication Date | Jan 12, 2021 |
Publication Date | 2021-02 |
Deposit Date | Jan 19, 2022 |
Publicly Available Date | Mar 29, 2024 |
Journal | Vadose Zone Journal |
Electronic ISSN | 1539-1663 |
Publisher | Soil Science Society of America |
Peer Reviewed | Peer Reviewed |
Volume | 20 |
Issue | 1 |
Article Number | e20096 |
DOI | https://doi.org/10.1002/vzj2.20096 |
Public URL | https://uwe-repository.worktribe.com/output/8545535 |
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On the laboratory calibration of dielectric permittivity models for agricultural soils: Effect of systematic porosity variation
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Licence
http://creativecommons.org/licenses/by/4.0/
Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/
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