THE MEASUREMENT OF SOIL WATER CONTENT USING A PORTABLE TDR HAND PROBE

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Abstract
The time-domain reflectrometry (TDR) technique had previously been shown to measure the volumetric water content of soil accurately when applied to long-term installations of parallel transmission lines. In this study a hand probe was used with a portable TDR instrument to measure water content of soil down the wall of soils pits to a depth greater than 1 m. In a separate experiment the water content of the surface soil at two sites was measured repeatedly in increasing depth increments of 50 mm to 300 mm. The TDR measured values were compared with values obtained by a gravimetric determination on a sample of soil. The TDR gave values that were calculated at the time of measurement in the field. TDR measured values were as accurate and precise as those from gravimetric samples. Key words: Volumetric water content, soil, time domain reflectometry