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@ARTICLE{DomnguezNio:863833,
      author       = {Domínguez-Niño, Jesús María and Bogena, Heye Reemt and
                      Huisman, Johan Alexander and Schilling, Bernd and
                      Casadesús, Jaume},
      title        = {{O}n the {A}ccuracy of {F}actory-{C}alibrated {L}ow-{C}ost
                      {S}oil {W}ater {C}ontent {S}ensors},
      journal      = {Sensors},
      volume       = {19},
      number       = {14},
      issn         = {1424-8220},
      address      = {Basel},
      publisher    = {MDPI},
      reportid     = {FZJ-2019-03813},
      pages        = {3101 -},
      year         = {2019},
      abstract     = {Soil water content (SWC) monitoring is often used to
                      optimize agricultural irrigation. Commonly, capacitance
                      sensors are used for this task. However, the factory
                      calibrations have been often criticized for their limited
                      accuracy. The aim of this paper is to test the degree of
                      improvement of various sensor- and soil-specific calibration
                      options compared to factory calibrations by taking the 10HS
                      sensor as an example. To this end, a two-step sensor
                      calibration was carried out. In the first step, the sensor
                      response was related to dielectric permittivity using
                      calibration in media with well-defined permittivity. The
                      second step involved the establishment of a site-specific
                      relationship between permittivity and soil water content
                      using undisturbed soil samples and time domain reflectometry
                      (TDR) measurements. Our results showed that a model, which
                      considered the mean porosity and a fitted dielectric
                      permittivity of the solid phase for each soil and depth,
                      provided the best fit between bulk permittivity and SWC.
                      Most importantly, it was found that the two-step calibration
                      approach (RMSE: 1.03 $vol.\%)$ provided more accurate SWC
                      estimates compared to the factory calibration (RMSE: 5.33
                      $vol.\%).$ Finally, we used these calibrations on data from
                      drip-irrigated almond and apple orchards and compared the
                      factory calibration with our two-step calibration approach.},
      cin          = {IBG-3},
      ddc          = {620},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31337053},
      UT           = {WOS:000479160300068},
      doi          = {10.3390/s19143101},
      url          = {https://juser.fz-juelich.de/record/863833},
}