Currently, the 5TE sensor (Decagon Inc.) is widely used for monitoring soil water content and electrical conductivity. A practical calibration method and validation of the values recorded by the 5TE are required for volcanic ash soils. We investigated a simple correction method to estimate the soil water content (
θ) and showed that a calibration approach with a few ( or even one ) points could be used to correct 5TE readings. We also validated estimation method of 1:5 soil to water extract electrical conductivity (
EC1:5) and soil pore water electrical conductivity (
ECp) with the 5TE.
EC1:5 was obtained based on a proportional relation with bulk electrical conductivity (
ECa) , and
ECp could be estimated from
ECa using the Hilhorst model with a simple calibration. However, the measurement accuracy of the 5TE decreased when
ECp>1.0 S/m for Toyoura sand and
ECp>0.8 S/m for Gandai soil. When
θ<0.2 for Toyoura sand and
θ<0.275 for Gandai soil, the 5TE could not estimate the
ECp. This should be considered when analyzing water content and electrical conductivity values measured in the field with 5TE.
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