A Simple Method for Calibrating Dielectric Soil Moisture Sensors: Laboratory Validation in Sands

作者：Sakaki Toshihiro^*; Limsuwat Anuchit; Illangasekare Tissa H

来源：Vadose Zone Journal, 2011, 10(2): 526-531.

DOI：10.2136/vzj2010.0036

With the goal of an effective method for calibrating dielectric soil moisture sensors that can be implemented rapidly, the applicability of a two-point alpha-mixing model was examined for a variety of sensor types. A large number of sensor outputs (X) were taken for four different types of ECH(2)O soil moisture sensors under varying volumetric water contents (theta) using four test sands with various grain sizes. The two-point alpha-mixing model was fitted to the X-theta data and a fitting parameter, alpha, was determined for each sensor type. Two other widely used sensors, the CS616 and the ThetaProbe ML2x, were also tested using the calibration functions and data provided by the manufacturers, including data for a soil with high electrical conductivity. For the sensors tested in this study, the effects of sensor characteristics were lumped into alpha. The value of alpha was 1.0 to 4.6, generally with high r(2) values. Some of these were as accurate as polynomial models that require a large number of X-theta data. After the alpha value is fitted for a specific sensor type, the two-point alpha-mixing model requires only the measurement of porosity and two extreme X values, i.e., sensor outputs in dry and saturated soils, and does not require soil samples with intermediate water content. Therefore, the two-point alpha-mixing model can be considered as an alternative method for calibrating dielectric soil moisture sensors, especially when porosity is known with small uncertainty such as relatively homogeneous field or laboratory experiments.

• 出版日期2011-5