TITLE:
Performance of Hydra Probe and MPS-1 Soil Water Sensors in Topsoil Tested in Lab and Field
AUTHORS:
Gerhard Kammerer, Reinhard Nolz, Marek Rodny, Willibald Loiskandl
KEYWORDS:
Water Content, Matric Potential, Temperature
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.6 No.13,
September
29,
2014
ABSTRACT: Soil water
sensors are commonly used to monitor water content and matric potential in order
to study hydrological processes such as evaporation. Finding a proper sensor is
sometimes difficult, especially for measurements in topsoil, where changes of temperature
and soil water dynamics occur generally with greater intensity compared to deeper
soil layers. We assessed the perfor-mance of Hydra Probe water content sensors and
MPS-1 matric potential sensors in topsoil in the laboratory and in the field. A
common soil-specific calibration function was determined for the Hydra Probes. Measurement
accuracy and sensor-to-sensor variation were within the manufacturer specification
of ±0.03 m3·m-3. Hydra Probes can operate from dry to saturated conditions.
Sensor-specific calibrations from a previous study were used to reduce sensor-to-sensor
variation of MPS-1. Measurement accuracy can be expressed by a mean relative error
of 10%. According to the manufacturer, the application range of matric potential
readings is from -10 kPa to -500 kPa. MPS-1 delivered also values beyond this range,
but they were not reliable. Sensor electronics of the MPS-1 were sensitive to ambient
temperature changes. Beyond instrument effects, field measurements showed substantial
temperature-driven fluctuations of soil water content and matric potential, which
complicated data interpretation.