06 Jan 2023
06 Jan 2023
Status: this preprint is open for discussion.

Reproducibility of the Wet Part of the Soil Water Retention Curve: A European Interlaboratory Comparison

Benjamin Guillaume1, Hanane Aroui Boukbida2, Gerben Bakker3, Andrzej Bieganowski4, Yves Brostaux1, Wim Cornelis5, Wolfgang Durner6, Christian Hartmann2, Bo V. Iversen7, Mathieu Javaux8, Joachim Ingwersen13, Krzysztof Lamorski4, Axel Lamparter9, András Makó10, Ana María Mingot Soriano11, Ingmar Messing11, Attila Nemes12, Alexandre Pomes-Bordedebat1, Martine van der Ploeg3, Tobias Weber Karl David13, Lutz Weihermüller14, Joost Wellens1, and Aurore Degré1 Benjamin Guillaume et al.
  • 1Uliège - Gembloux Agro-Bio Tech, TERRA Teaching and Research Centre, Passage des Déportés 2, 5030 Gembloux, Belgium
  • 2Instrumentation, Moyens Analytiques, observatoire en Géophysique et Océanographie (UAR IMAGO), Institut de Recherche pour le Développement (IRD)
  • 3Wageningen University and Research, Netherlands
  • 4Institute of Agrophysics, Polish Academy of Sciences, Poland
  • 5Ghent University, Belgium
  • 6Technische Universität Braunschweig, Germany
  • 7Department of Agroecology, Aarhus University, Denmark
  • 8UCLouvain, Earth and Life Institute, Belgium
  • 9Federal Institute for Geosciences and Natural Resources, Germany
  • 10Department of Soil Physics and Water Management, Institute for Soil Sciences, Centre for Agricultural Research, Herman Ottó street 15, 1022 Budapest, Hungary
  • 11Swedish University of Agricultural Sciences, Sweden
  • 12Norwegian Institute of Bioeconomy Research, Norway
  • 13Institute of Soil Science and Land Evaluation, University of Hohenheim, Germany
  • 14Agrosphere Institute IBG-3, Forschungszentrum Jülich GmbH, Germany

Abstract. The soil water retention curve (SWRC) is a key soil property required for predicting basic hydrological processes. SWRC is often obtained in laboratory with non-harmonized methods. Moreover, procedures associated to each method are not standardized. This can induce a lack of reproducibility between laboratories using different methods and procedures or using the same methods with different procedures. The goal of this study was to estimate the inter/intralaboratory variability of the measurement of the wet part (from 10 to 300 hPa) of the SWRC. An interlaboratory comparison was conducted between 14 laboratories, using artificially constructed, porous and structured samples as references. The bulk densities of samples were different at the very beginning of the experiment. This resulted in a variability of retention properties between the samples, which was estimated by a linear mixed model with a "sample" random effect. Our estimate of inter/intralaboratory variability was therefore not affected by intrinsic differences between samples. The greatest portion of the differences in the measurement of SWRCs was due to interlaboratory variability. The intralaboratory variability was highly variable depending on the laboratory. Some laboratories successfully reproduced the same SWRC on the same sample, while others did not. The mean intralaboratory variability over all laboratories was smaller than the mean interlaboratory variability. A possible explanation for these results is that all laboratories used slightly different methods and procedures. We believe that this result may be of great importance regarding the quality of SWRC databases built by pooling SWRCs obtained in different laboratories. The quality of pedotransfer functions or maps that might be derived is probably hampered by this inter-/intralaboratory variability. The way forward is that measurement procedures of the SWRC need to be harmonized and standardized.

Benjamin Guillaume et al.

Status: open (until 17 Feb 2023)

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  • RC1: 'Comment on egusphere-2022-1496', Anonymous Referee #1, 26 Jan 2023 reply

Benjamin Guillaume et al.

Benjamin Guillaume et al.


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Short summary
Measurements of soil water retention properties play an important role in a variety of societal issues that depend on soil-water conditions. However, there is little concern about the consistency of these measurements between laboratories. We conducted an interlaboratory comparison to assess the reproducibility of the measurement of the soil water retention curve. Results highlight the need to harmonize and standardize procedures to improve the description of unsaturated processes in soils.