Reproducibility of the wet part of the soil water retention curve: a European interlaboratory comparison

Summary

This European interlaboratory study reveals substantial variability in soil water retention curve measurements, with interlaboratory differences exceeding intralaboratory variability across 14 participating laboratories. The authors attribute these differences primarily to non-standardised and non-harmonised measurement methods and procedures. The findings raise important quality concerns for soil property databases derived from multiple laboratories and suggest that harmonisation and standardisation of SWRC measurement procedures is necessary to improve the reliability of pedotransfer functions and soil maps.

UK applicability

These findings are directly applicable to UK soil science and hydrology research, where SWRC data from multiple laboratories are routinely integrated into national soil property databases and pedotransfer function development. The recommendations for harmonisation and standardisation of measurement procedures would benefit UK soil monitoring networks, hydrological modelling efforts, and the quality of soil-water property information used in environmental impact assessments and land management planning.

Key measures

Inter- and intralaboratory variability in soil water retention measurements; sample-to-sample variability; effects of sample changes between measurements; interlaboratory variability, intralaboratory variability, and sample change effects in SWRC measurements; matric potential range 10–300 hPa

Outcomes reported

The study quantified inter- and intralaboratory variability in measurements of the wet part of the soil water retention curve (10–300 hPa) across 14 European laboratories using standardised reference samples. Results demonstrated that interlaboratory variability was the largest source of measurement differences, with substantial variation in intralaboratory reproducibility between laboratories. Bayesian linear mixed modelling was used to partition variability sources and assess the reproducibility of SWRC measurements.

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