Moisture–Conductivity Calibration for Electrical Imaging of Horticultural Substrate

Peng-Fei Zhao, Li-Feng Fan, Yong-Qian Wang, Yang Li, Nan Wang, Zhong-Yi Wang, Qiang Cheng and Lan Huang
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Peng-Fei Zhao: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Li-Feng Fan: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Yong-Qian Wang: School of Instrument Science and Opto Electronic Engineering, Beijing Information Science and Technology University, Beijing 100192, China
Yang Li: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Nan Wang: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Zhong-Yi Wang: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Qiang Cheng: College of Information and Electrical Engineering, China Agricultural University, Beijing 100083, China
Lan Huang: Key Laboratory of Agricultural Information Acquisition Technology (Beijing), Ministry of Agriculture, Beijing 100083, China

Agriculture, 2021, vol. 11, issue 9, 1-24

Abstract: Electrical imaging studies of laboratory- and small-scale plant root zones are gaining increasing attention. However, for essential moisture–conductivity calibrations on numerous substrate columns with variability in dry density, the use of one conventional strategy is relatively laborious or complicated. Thus, in this work, a relatively convenient calibration method is presented, and the objective is to identify its feasibility and potential to assess the effects of factors (e.g., volumetric water content (VWC), and dry density) on conductivity and establish necessary moisture–conductivity curves for porous materials (e.g., soils and substrates). In the method, with a specially designed fixture, variable VWCs, dry densities and related complex conductivities of the samples can be easily acquired through static compaction. The results show that the in-phase conductivity (or magnitude of conductivity) increases with the increasing VWC or dry density, primarily owing to the increase in the dominant pore water connectivity. Moreover, the effect of dry density on conductivity is relatively smaller than that of VWC. Thus, for the substrates at dry densities with certain variability, good power law relations ( R 2 ≥ 0.99) between in-phase conductivity (or magnitude of conductivity) and VWC at different frequencies can be established. Overall, the proposed approach is practical, promising, and relatively time- and labor-saving.

Keywords: horticultural substrate; complex conductivity; frequency; moisture; density; calibration (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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