The application of TDR in laboratory column experiments

• Published in: Soil technology Vol. 6; no. 3; pp. 261 - 272
• Main Authors: Heimovaara, T.J., Freijer, J.I., Bouten, W.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 1993; Amsterdam Elsevier; New York, NY
• Subjects: Agronomy. Soil science and plant productions; automation; Biological and medical sciences; Entisols; evaporation; Fundamental and applied biological sciences. Psychology; hysteresis; laboratory techniques; measurement; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; pressure; pressure head; soil analysis; Soil science; soil water; soil water content; soil water retention; tensiometers; time domain reflectometry; unsaturated flow; unsaturated hydraulic conductivity; Water and solute dynamics; Water infiltration; Laboratory study; Soils; Soil column; Time domain method; Water content; Reflectometry; Hydraulic conductivity; Method; Evaporation; Entisols; Hydraulic properties
• ISSN: 0933-3630
• DOI: 10.1016/0933-3630(93)90015-7

An automated TDR system was used together with an automated tensiometer system in laboratory column experiments for the measurement of unsaturated hydraulic properties of soils. The laboratory experiments were a stationary flux (sprinkling infiltrometer) carried out with different fluxes, and a transient (evaporation) method. Simultaneous measurements of water content and pressure head give the water retention characteristic and enable the application of the instantaneous profile analysis for calculating the hydraulic conductivity. This direct analysis is compared with the traditional analysis methods normally used for the laboratory experiments. The application of automated measurement techniques and the use of TDR increases the speed of the measurements, generates more data points and requires less assumptions in the data analysis. Moreover, TDR measurements give insight in the flow process, including effects of hysteresis and heterogeneity within a sample. Performing the sprinkling infiltrometer and evaporation experiments on the same sample enables the determination of the unsaturated hydraulic conductivity at pressure heads ranging from −0.01 m to −6 m.