
TY  - JOUR
A1  - Geesing, Dieter 
A1  - Bachmaier, Martin 
A1  - Schmidhalter, Urs 
T1  - Field calibration of a capacitance soil water probe in heterogeneous fields
JF  - Soil Research
JO  - Soil Res.
Y1  - 2004
VL  - 42
IS  - 3
SP  - 289
EP  - 299
KW  - soil water variability, site-specific calibration, portable capacitance probe, soil water monitoring.
UR  - https://doi.org/10.1071/SR03051 
N2  - Soil water research requires methods to perform accurate measurements. A capacitance probe gauge has characteristics that seem to make it an attractive replacement for neutron scatter gauges to measure soil water content, but there is evidence that capacitance systems should be calibrated for individual soils. Laboratory calibrations and many field calibration methods are costly and time-consuming, and controlled conditions and disturbed soil samples do not always reflect field conditions, and thus, they are inadequate for practical use. The objectives of the present study were (i) to test a simple field calibration method for a recently developed capacitive sensor even under highly variable soil texture conditions, and (ii) to validate this approach under various soil moisture conditions. Soil samples were taken 0.5 m from the access tube of the sensor and a whole field calibration and several site-specific calibrations were developed using 10&#8211;142 observations per site under different soil water regimes. A regression of soil water content estimated by sensor reading on water content obtained by core sampling showed no significant difference in the slope and intercept of the 1:1 line when the field calibration was applied. However, the precision of the calibration was only considerably increased if the estimations were based on site-specific calibrations developed on at least 35 observations per site. The precision and accuracy of the calibration equations were not affected when data were obtained only under wet or dry soil conditions. The method presented in this paper is a speedy and cheap way to calibrate capacitance probe sensors. 
ER  -

