Abstract
Abstract. Soil water content and matric potential are central hydrological state variables. A large variety of automated probes and sensor systems for state monitoring exist and are frequently applied. Most applications solely rely on the calibration by the manufacturers. Until now, there has been no commonly agreed-upon calibration procedure. Moreover, several opinions about the capabilities and reliabilities of specific sensing methods or sensor systems exist and compete. A consortium of several institutions conducted a comparison study of currently available sensor systems for soil water content and matric potential under field conditions. All probes were installed at 0.2 m b.s. (metres below surface), following best-practice procedures. We present the set-up and the recorded data of 58 probes of 15 different systems measuring soil moisture and 50 further probes of 14 different systems for matric potential. We briefly discuss the limited coherence of the measurements in a cross-correlation analysis. The measuring campaign was conducted during the growing period of 2016. The monitoring data, results from pedophysical analyses of the soil and laboratory reference measurements for calibration are published in Jackisch et al. (2018, https://doi.org/10.1594/PANGAEA.892319).
Highlights
Soil water content is defined as the volumetric proportion of water in the multiphase bulk soil
Since the proposition of soil moisture determination based on relative electrical permittivity of the bulk soil in the 1970s many commercially available systems have been developed
They can be roughly grouped into timedomain reflectometry (TDR), mostly impedance-based determination of the capacitance and time-domain transmission (TDT) techniques, which all rely on the strong contrast of the relative electrical permittivity of water (80) with air (1) and minerals (3–5) in the bulk soil
Summary
Soil water content is defined as the volumetric proportion of water in the multiphase bulk soil. Since the proposition of soil moisture determination based on relative electrical permittivity of the bulk soil in the 1970s (presumably starting with Davis et al, 1966; Geiger and Williams, 1972; Chudobiak et al, 1979) many commercially available systems have been developed. One has to be aware that the theoretically more appropriate TDR technology might not deliver more precise readings per se when technical issues obscure the actual measurement Another common assumption relates to a large sensing volume being more favourable. Accompanying soil water content, matric potential is the second central hydrological state variable of soils It is an integral over the macroscopic interfacial tension of the porescale menisci of all air–water–soil interfaces. In order to identify conceptual limits and technological issues of currently available systems for measurement of soil water content and matric potential we conducted a comparison study under field conditions.
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