Articles
IN SITU MONITORING WATER CONTENT AND ELECTRICAL CONDUCTIVITY IN SOILLESS MEDIA USING A FREQUENCY-DOMAIN SENSOR
Article number
562_34
Pages
295 – 303
Language
English
Abstract
A frequency-domain (FD) sensor with four cm long electrodes was calibrated for measurement of volumetric water content(
), and EC for use in horticultural growing media.
The calibrations were conducted under laboratory conditions in solution, rockwool and potting media.
Linear relations between permittivity
(dielectric constant) and bulk electrical conductivity (ECb) were found in rockwool, allowing to estimate the EC of the medium solution (ECms) up to at least 6 mS/cm after temperature correction.
Volumetric water content () was highly correlated with after temperature and EC-corrrections (c), and appeared to be independent of bulk density in mineral wool.
The sensor was used for determining vertical differences inc in 6.5 cm high rockwool cubes used for rose propagation.
In organic media such as potting soil used for ebb-and flow fertigation, linear relations between and ECb were found as well.
However, sensitivity to differences in ECms was lower in these organic media than in rockwool.
ECms could be estimated reliably up to 3 mS/cm.
Thec and ECms were measured in potting soil during ebb-and flow cycles under greenhouse conditions.
This in situ measuring showed that ECms increased at decreased. Practical implications for use of the sensor are adressed.
Additional index words: ebb/flow cultivation, EC, hydroponics, root alcohol dehydrogenase activity, salinity
), and EC for use in horticultural growing media.The calibrations were conducted under laboratory conditions in solution, rockwool and potting media.
Linear relations between permittivity
(dielectric constant) and bulk electrical conductivity (ECb) were found in rockwool, allowing to estimate the EC of the medium solution (ECms) up to at least 6 mS/cm after temperature correction.Volumetric water content (
) was highly correlated with after temperature and EC-corrrections (c), and appeared to be independent of bulk density in mineral wool.The sensor was used for determining vertical differences in
c in 6.5 cm high rockwool cubes used for rose propagation.In organic media such as potting soil used for ebb-and flow fertigation, linear relations between
and ECb were found as well.However, sensitivity to differences in ECms was lower in these organic media than in rockwool.
ECms could be estimated reliably up to 3 mS/cm.
The
c and ECms were measured in potting soil during ebb-and flow cycles under greenhouse conditions.This in situ measuring showed that ECms increased at decreased
. Practical implications for use of the sensor are adressed.Additional index words: ebb/flow cultivation, EC, hydroponics, root alcohol dehydrogenase activity, salinity
Authors
R. Baas, N.A. Straver
Keywords
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