Articles
MEASURE OF SUBSTRATES UNSATURATED HYDRAULIC CONDUCTIVITY (REFEREED)
Article number
450_35
Pages
297 – 304
Language
Abstract
A computerized apparatus has been devised to measure unsaturated hydraulic conductivity of horticultural substrates with the long-column version of the steady-state flux control method, consisting of a pumping system (CCSA) and a long column.
The CCSA consists of three connected units: a mechanic device that provides a constant water flux by means of a set of two syringe pumps of different piston area with double direction, an electronic part that acts as an interface between the mechanical device and a computer and that controls a step by step engine and detection systems, and a computer software developed in C language that sets ranges of start and working times.
These units allow to apply a constant water flux to a column containing the substrate sample, where four pressure transducer-tensiometers control pressure head.
Program provides a user interface with several options; with these one can set the CCSA to change flow rates at given times.
The CCSA allows for future improvements, such as changes in column length, operation at controlled gas pressure, computer control of tensiometers, and complete computerized control of apparatus from sensor measurements.
Expanded perlite has been used to assess performance of CCSA. Obtained results for unsaturated hydraulic conductivity have been compared with those calculated with Van Genuchten’s analytical method.
There is good agreement between experimental and calculated results when saturation of sample is done at atmospheric pressure and this value is used as an input for the analytical model.
Accurately obtaining saturation porosity is very important when applying Van Genuchten’s analytical method and specially when substrates have internal porosity.
The CCSA consists of three connected units: a mechanic device that provides a constant water flux by means of a set of two syringe pumps of different piston area with double direction, an electronic part that acts as an interface between the mechanical device and a computer and that controls a step by step engine and detection systems, and a computer software developed in C language that sets ranges of start and working times.
These units allow to apply a constant water flux to a column containing the substrate sample, where four pressure transducer-tensiometers control pressure head.
Program provides a user interface with several options; with these one can set the CCSA to change flow rates at given times.
The CCSA allows for future improvements, such as changes in column length, operation at controlled gas pressure, computer control of tensiometers, and complete computerized control of apparatus from sensor measurements.
Expanded perlite has been used to assess performance of CCSA. Obtained results for unsaturated hydraulic conductivity have been compared with those calculated with Van Genuchten’s analytical method.
There is good agreement between experimental and calculated results when saturation of sample is done at atmospheric pressure and this value is used as an input for the analytical model.
Accurately obtaining saturation porosity is very important when applying Van Genuchten’s analytical method and specially when substrates have internal porosity.
Authors
S. Burés, O. Marfà, T. Pérez, J. Tébar, A. Lloret
Keywords
analytical models, container media, perlite, physical properties
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