An improved formula for evaluating electrical capacitance using the dissipation factor

Imre Cseresnyés, Sándor Kabos, Tünde Takács, Krisztina R. Végh, Eszter Vozáry, K. Rajkai

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Abstract

Background and aims: The measurement of electrical capacitance in root–soil system (CR) is a useful method for estimating the root system size (RSS) in situ; however, CR–RSS regressions are often poor. It was hypothesized that this weak relationships could be partly due to the variable energy-loss rate, indicated by the dissipation factor (DF). Methods: The values of CR and the associated DF were measured in six plant species grown in quasi-hydroponic pumice medium, arenosol and chernozem soil. The dielectric properties of the plant growth media were also recorded. A modified root–soil capacitance, CDF, was calculated from each CR/DF pair according to the formula CDF = CR·(DF/DFmean)α by estimating α with a standard nonlinear minimization of the sum of squared residuals for CDF–RSS regressions. Results: The capacitive behavior of the medium improved (mean DF decreased) but fluctuated increasingly as the substrate became more complex. The mean DF values in plant–substrate systems were chiefly determined by the plant and were the most variable in chernozem soil. This strengthening substrate effect on CR measurements appeared as a decreasing trend in the R2 values obtained for the CR–RSS regressions. The regression slope was influenced by plant species and medium, while the y-intercept differed only between substrate types. The proposed use of CDF in place of CR could significantly improve the R2 of CDF–RSS regressions, particularly in chernozem soil (R2 increased by 0.07–0.31). Conclusions: The application of CDF will provide more reliable and accurate RSS estimations and more efficient statistical comparisons. The findings are worth considering in future investigations using the root capacitance method.

Original languageEnglish
Pages (from-to)237-256
Number of pages20
JournalPlant and Soil
Volume419
Issue number1-2
DOIs
Publication statusPublished - Oct 1 2017

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Keywords

  • Complex permittivity
  • Dissipation factor
  • Plant–soil system
  • Root electrical capacitance
  • Root system size
  • Soil dielectric

ASJC Scopus subject areas

  • Soil Science
  • Plant Science

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