ISHS Acta Horticulturae 807: International Symposium on Strategies Towards Sustainability of Protected Cultivation in Mild Winter Climate
THE CALIBRATION OF WET-SENSOR FOR VOLUMETRIC WATER CONTENT AND PORE WATER ELECTRICAL CONDUCTIVITY IN DIFFERENT HORTICULTURAL SUBSTRATES |
| Authors: | L. Incrocci, G. Incrocci, A. Pardossi, G. Lock, C. Nicholl, J. Balendonck |
| Keywords: | growing media, root zone sensor, peat, pumice, perlite |
| Abstract:
A frequency domain dielectric sensor (WETŪ), which measures permittivity (  ), temperature (T, °C) and bulk electrical conductivity (σ, dS/m) simultaneously in the same soil volume, was calibrated for the volumetric water content ( , m3 m-3) and the salinity of both pore water (σP) and water extract (σE) in different horticultural substrates: peat, pumice, perlite, peat-perlite and peat-pumice.
The experiment was conducted under laboratory conditions over a T range between 22 and 28°C using plastic pots filled with each substrate, irrigated to fully container capacity with nutrient solutions of known concentrations and let to dry (in air) to ranging from approx. 0.20 and 0.50 m3 m-3. In order to avoid the development of significant gradients in substrate moisture and salinity, the pots did not host plants and the evaporation from the top surface was prevented by means of a plastic wrap.
Pore water was collected by centrifugation, whereas water extract was obtained by means of 1 substrate: 2 water suspension method.
The values of both and σ were corrected for T. The main results of the experiment are the following: i) calibration was faintly dependent on the type of substrate and was only slightly affected by the salinity of irrigation water; ii) a significant linear relationship was found between σE and σP, with the slope dependent on the type of substrate; iii) the linear relationship of against was highly significant and unaffected by the salinity of irrigation water; iv) at least in the peat-pumice mixture, the only substrate used for this kind of calibration, the linear regression between σ and σP was markedly affected by , since the slope decreased with increasing .
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