Calibrating electromagnetic short soil water sensors

• Published in: Journal of Hydrology and Hydromechanics Vol. 58; no. 2; pp. 114 - 125
• Main Authors: Loiskandl, W., University of Natural Resources and Applied Life Sciences, Vienna (Austria), Buchan, D. G., Lincoln University, Canterbury (New Zealand), Sokol, W., University of Natural Resources and Applied Life Sciences, Vienna (Austria), Novak, V., Slovak Academy of Sciences, Bratislava (Slovak Republic). Institute of Hydrology, Himmelbauer, M., University of Natural Resources and Applied Life Sciences, Vienna (Austria)
• Format: Journal Article
• Language: English
• Published: Bratislava Versita 01.06.2010; De Gruyter Poland; Sciendo
• Subjects: Accuracy; Calibration; CAMPO ELECTROMAGNETICO; CHAMP ELECTROMAGNETIQUE; CONTENIDO DE AGUA EN EL SUELO; ELECTROMAGNETIC FIELD; Electromagnetic Probes; elektromagnetické snímače; http://www.fao.org/aos/agrovoc#c_34267; http://www.fao.org/aos/agrovoc#c_36855; http://www.fao.org/aos/agrovoc#c_7208; kalibrácia; REFLECTOMETRIA; REFLECTOMETRIE; REFLECTOMETRY; Sensors; snímače vlhkosti pôdy; Soil Moisture Probes; SOIL WATER CONTENT; TDR; TENEUR EN EAU DU SOL
• ISSN: 0042-790X; 1338-4333
• DOI: 10.2478/v10098-010-0011-3

The use of electromagnetic (EM) soil moisture probes is proliferating rapidly, in two broad domains: in field and laboratory research; and in strongly practical applications such as irrigation scheduling in farms or horticultural enterprises, and hydrological monitoring. Numerous commercial EM probes are available for measurement of volumetric water content (θv), spanning a range of measurement principles, and of probe dimensions and sensing volumes. However probe calibration (i.e. the relationship of actual 9V to probe electrical output) can shift, often substantially, with variations in parameters such as soil texture, or­ganic matter content, wetness range, electrical conductivity and temperature. Hence a single-valued, manu­facturer-supplied calibration function is often inadequate, forcing the user to seek an application-specific calibration. The purpose of this paper is to describe systematic procedures which probe users can use to check or re-determine the calibration of their selected probe(s). Given the wide diversity of operating prin­ciples and designs of commercially-available EM probes, we illustrate these procedures with results from our own calibrations of five different short probes (length of 5 to 20 cm). Users are strongly recommended to undertake such calibration checks, which provide both a) pre-use experience, and b) more reliable in-use data.